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Submitted to:

Mr. Blair Bennett

Soprema Inc.

#101 - 18651 52nd Avenue

Surrey BC V3S 8E5

Mr. Dave Lawlor

Roxul Inc.

#105 - 420 Bronte Street South

Milton, ON L9T 0H9

Submitted Sept. 14, 2014 by:

RDH Building Engineering Ltd.

224 W 8th Avenue

Vancouver BC V5Y 1N5

6230_00 2014 12 15 LR GF RPT - Conventional Roof Monitoring Study.docm

Contents

1 Introduction 1

1.1 Background 1

1.1.1 Durability 2

1.1.2 Heat Flow & Energy Consumption 2

1.2 Objectives 3

1.3 Methodology & Scope 4

1.3.1 Laboratory Testing 4

1.3.2 Field Monitoring 5

1.3.3 Energy Modeling 13

2 Laboratory Results 14

3 Field Monitoring Results 17

3.1 Overview of Boundary Conditions 17

3.2 Thermal Performance - Membrane Cap Sheet Colour 19

3.2.1 Membrane In-Service Reflectance 19

3.2.2 Membrane Temperature 24

3.2.3 Membrane Degradation 27

3.2.4 Urban Heat Island 30

3.2.5 Heat Flux 31

3.2.6 Interior Metal Deck Temperature 32

3.3 Thermal Performance - Insulation Arrangement 34

3.3.1 Heat Flux 34

3.3.2 Membrane Temperature 35

3.3.3 Interior Metal Deck Temperature 37

3.3.4 Insulation Thermal Mass 38

3.3.5 Latent Heat Transfer 39

3.4 Dimensional Stability of Insulation 41

3.4.1 Long-term Displacement 42

3.4.2 Short-term Displacement 47

4 Energy Modeling 49

5 Discussion and Conclusions 54

6 Further Research 56

7 References 57

Contents (continued)…

6230_00 2014 12 15 LR GF RPT - Conventional Roof Monitoring Study.docm

Appendices

Appendix A Additional Graphs

6230.00 RDH Building Engineering Ltd. Page 1

1 Introduction

Conventional roof assemblies make-up the majority of low-slope roof assemblies in North

America. The design of these roof assemblies typically considers a variety of factors

including product availability, economics, aesthetics, energy consumption, building type,

local industry familiarity, and compliance with building codes and green building programs;

however, the implications of these selections are often not fully understood. Factors

including membrane colour and insulation type can have significant impacts on the thermal

performance of the roof assembly and consequently on building energy consumption,

occupant comfort, membrane durability, and assembly service life.

This research study analyzes the performance of nine different roof assemblies with

different membrane colour (white, grey, and black) and insulation arrangements

(polyisocyanurate, stone wool, and hybrid) with respect to energy transfer and membrane

durability. This assessment includes consideration of insulation thermal mass, insulation

age, insulation dimensional stability, latent heat transfer, roof membrane reflectance1, roof

membrane soiling, and roof membrane temperatures.

1.1 Background

Conventional roof assemblies, also known as exposed membrane roof assemblies, are roofs

which have the roof membrane on the exterior of the roof insulation and structure.

Typically there is also an air and vapour barrier membrane installed on the underside of the

roof insulation to prevent condensation and associated damaged within the roof assembly.

Various types of insulation are used within conventional roof assemblies including rigid

polyisocyanurate (polyiso, approximately R-5 to R-6 ft²∙°F∙hr/Btu per inch), expanded

polystyrene (EPS, approximately R-4 to R-4.5 ft²∙°F∙hr/Btu per inch), or rigid stone wool

(approximately R-3.7 to R-4.3 ft²∙°F∙hr/Btu per inch). Wood fiberboard, rigid fiberglass,

extruded polystyrene (XPS), and spray polyurethane foam (SPF) insulation are also used in

conventional roofs, but are less common. It is also possible to use a combination of

insulation layers within conventional roofs, thus blending the positive attributes of each

insulation type in “hybrid” systems. One common example of a hybrid system is to use EPS

insulation to achieve the required slope, and then use polyiso insulation for the majority of

the insulation due to its high R-value per inch of thickness.

While insulation products are typically rated based on their thermal resistance at the time

of manufacture according to standardized test procedures, this testing does not consider

in-service temperatures, and potential latent heat transfer. Additionally, the impacts of

insulation thermal mass and roof membrane temperatures on net heat flow, and

subsequently on building energy consumption and membrane durability, are not typically

considered. For the purposes of this study, rated R-value refers to the R-value of the

insulation per the manufacturer’s specifications, and apparent R-value refers to the in-

service R-value of the insulation including the effects of temperature dependent

conductivities and aging.

1 For readability, this report uses the term “reflectance” to refer to the ability of the surface (i.e. membrane) to reflect radiation (i.e. solar radiation) in all directions measured as a fraction of the incident radiation; however, this is more accurately referred to as “albedo” and “reflectance” technically is only for a specific incident angle.

RDH Building Engineering Ltd. 6230.00

Different roof membrane colours are also used in conventional roof assemblies. Reflective

roof membranes are typically selected to provide increased reflection of solar radiation

thereby decreasing roof membrane temperature and urban heat island effect, and often this

selection is part of meeting green building program requirements. However, much of the

work with regards to reflective roofs does not consider the effects of soiling as roof

membranes age.

This study addresses durability and thermal performance of conventional roof assemblies

with respect to roof membrane colour and insulation arrangement.

1.1.1 Durability

Conventional roof assemblies (i.e. exposed roof assemblies) expose the waterproof

membrane to exterior conditions including exterior temperature, radiation from the sun

including ultraviolet (UV), precipitation, wind, atmospheric pollution and dirt. All of these

exposures can degrade the roof membrane, and its ability to resist this degradation

determines its durability and service life.

Temperature is of particular importance to roof membrane durability. Increased

temperature can “accelerate deleterious chemical reactions, cause loss of volatile

constituents, and soften some polymers” (pg. 424, Berdahl et al., 2008). Additionally,

thermal expansion and contraction due to changes in temperature can stress roof

membranes and can affect the durability of the membrane. (Berdahl et al., 2008) Typically

faster rates of dimensional change and larger magnitude changes will more rapidly degrade

a roof membrane and shorten its service life. (Dell, 1990)

It is well known that exposed roof membranes can reach temperatures significantly higher

than ambient air temperatures due to absorption of solar radiation. Consequently, the

absorptivity, and reflectivity of the roof can significantly impact of the roof temperatures

and thus roof membrane durability. A more reflective roof may cause a roof membrane to

heat up less quickly, and reduce both average and maximum membrane temperatures

which would likely extend the service life of the roof membrane.

The rate of change and magnitude of exposed roof membrane temperatures may also be

impacted by the thermal mass of the membrane substrate, which in conventional roofs is

provided by the insulation. Insulation with a higher thermal mass per square foot of roof

area may provide a buffer to changes in temperature. This buffer effect could potentially

change the net heat flow through the assembly and could also potentially act to moderate

roof membrane temperatures and extend its service life.

The dimensional stability of the roof membrane substrate (i.e. the insulation) can also

impact roof membrane durability. Typically foam insulations are less dimensionally stable

than mineral fibre insulations and movement of the insulation can potentially cause

creasing of the roof membrane and accelerate degradation due to increased strain induced

in the roof membrane.

1.1.2 Heat Flow & Energy Consumption

Heat flow through conventional assemblies, and consequently building energy

consumption, is also impacted by the combination of the roof membrane colour and the

insulation arrangement. Roof membranes with a higher Solar Reflective Index (SRI) are

commonly used in the Southern United States where regulated by energy standards such as


ASHRAE 90.1, and are also used in other areas as part of green building programs such as

Leadership in Energy and Environmental Design (LEED) which provides credits for use of a

high SRI roof. In northern climates the benefit of using white membrane roofs to achieve

cooling savings is often small and can be offset by higher wintertime heating loads. (DOE

Cool Roof Calculator, 2013; Roof Savings Calculator, 2013; Smith, 2001)

The insulation arrangement in a roof can also impact the heat flow through the assembly

and consequently the building energy consumption. Even for the same rated R-value,

different insulation types have different apparent thermal resistances due to operating

temperatures that are different than test conditions, and latent heat transfer. Additionally,

more thermally massive insulation types (such as stone wool) can buffer changes in a

temperature and consequently affect heat flow through roof assemblies.

In particular, it is generally recognized that the thermal resistance of polyiso insulation (and

some other foam insulations) decreases as it ages, and since circa 2001 most

manufacturers have reported the long-term thermal resistance (LTTR) of polyiso insulation.

(Roe, 2007; Christian et al., 1995) The LTTR is currently determined according to three

standards, the most recent versions of which are CAN/ULC-S770-09 Standard Test Method

for Determination of Long-term Thermal Resistance of Closed-Cell Thermal Insulating

Foams, or ASTM C1303-12 Standard Test Method for Predicting Long-Term Thermal

Resistance of Closed-Cell Foam Insulation. (Graham, 2013; Graham, 2014)

1.2 Objectives

This research study aims to evaluate the impact of roof membrane colour and insulation

type on the performance of conventional roof assemblies. In particular this study aims to

develop understanding in the following areas:

The difference in maximum and average roof membrane temperatures

The difference between rated and apparent in-service R-values for two common roof

insulations (polyiso and stone wool) due to the combination of in-service insulation

temperatures and aging effects

How membrane colour, insulation apparent R-value, and insulation thermal mass affect

net heat flow through different conventional roof assemblies

The potential interior surface temperature and thermal comfort benefits related to

membrane solar reflectance and roof insulation arrangement

The impact of aging and soiling on the reflectance of white SBS roof membranes

The in-service dimensional stability of two common roof insulations (polyiso and stone

wool)

The impact of insulation moisture content on latent heat transfer through conventional

roof assemblies

The impact of roof membrane colour and arrangement on whole building heating and

cooling energy consumption in various North American climates


1.3 Methodology & Scope

The experimental phase of this project includes three main components: laboratory testing

of insulation samples, field monitoring of roof assembly performance, and energy modeling

of building energy consumption implications.

1.3.1 Laboratory Testing

To determine the thermal resistance (R-value) of the insulation products being used in this

study, a number of polyiso and stone wool insulation samples were tested in general

accordance with ASTM C518 Standard Test Method for Steady-State Thermal Transmission

Properties by Means of Heat Flow Meter Apparatus (ASTM, 2010). This test method applies

a temperature difference across an insulation sample and measures the heat flux through

the sample under these conditions. A picture of the testing apparatus is shown in Figure

1.1.

Figure 1.1 Material conductivity testing machine used to measure insulation conductivity (Photo courtesy of Building Science Consulting Inc.)

Typically this test is performed at a mean temperature of 24°C (75°F) with a temperature

difference of approximately 28°C (50°F) across the insulation sample; however, this study

is also interested in the impact of temperature on the apparent R-value of the insulation

product, so the testing was also conducted at mean temperatures of -4°C, 4.5°C, 24°C, and

43°C (25°F, 40°F, 75°F, 110°F) with the same 28°C (50°F) temperature difference.

To investigate the impact of aging on the apparent R-value of polyiso insulation, three 4-

year-old samples were tested and six un-aged (approximately 2-month-old) samples were

tested. The 4-year-old samples were stored in laboratory conditions during the aging

period, and the six un-aged samples were removed from the same batches of insulation

installed in the test roofs for this research study.

Three stone wool insulation samples were also tested. These samples were removed from

the same batches of insulation installed in the test roofs for this research study.


1.3.2 Field Monitoring

A large-scale field monitoring program was implemented to evaluate the in-service

performance of conventional roof assemblies with three different colour membranes and

three different insulation arrangements for a total of 9 different roof assemblies. The three

roof membranes are all 2-ply SBS roof membranes with the same base sheet and a black,

grey, or white (LEED compliant SRI) granulated cap sheet. The three cap sheet colours are

shown in Figure 1.2, and the solar properties of the sheets as specified by the manufacturer

are provided in Table 1.1.

Figure 1.2 Samples of the three different SBS granulated cap sheet colour used in the field monitoring portion of this study

TABLE 1.1 ROOF MEMBRANE CAP SHEET PROPERTIES SPECIFIED BY MANUFACTURER

Cap Sheet Colour Solar Reflective

Index (SRI) Solar Reflectance

Thermal Emittance (Infrared)

White 70 0.582 0.91

Grey 9 0.138 0.85

Black -4 0.04 0.85

The three different insulation strategies are: all polyiso, all stone wool, and a hybrid roof

assembly with polyiso insulation underneath stone wool insulation. The hybrid system is

intended to optimize the apparent R-value of the polyiso insulation by maintaining it closer

to its optimal performance temperature, and also takes advantage of the dimensional

stability of the stone wool insulation. These three insulation assemblies are shown in Figure

1.3, Figure 1.4, and Figure 1.5 respectively.


Figure 1.3 Polyiso Roof Assembly – Two layers of polyiso insulation

Figure 1.4 Hybrid Roof Assembly – Base layer of polyiso insulation and top layer of stone wool insulation

Figure 1.5 Stone Wool Roof Assembly – Two layers of stone wool insulation

The thickness of the insulation layers in the roof assemblies were varied to achieve similar

rated R-values of approximately R-21.5 hr∙ft²∙°F/Btu based on values of R-6 hr∙ft²∙°F/Btu per

inch for the polyiso and R-3.8 hr∙ft²∙°F/Btu per inch for the stone wool. The layer thicknesses


and assembly rated R-values are provided below. The polyiso R-value (R-6 hr∙ft²∙°F/Btu per

inch) used to calculate the rated thermal performance of these assemblies was standard

practice at the start of the project; however, recently the methods of determination and

reporting of LTTR have been updated and typically lower values (R-5.6 hr∙ft²∙°F/Btu per inch)

are now reported. (Graham, 2014)

The rated R-values of the insulation installed in these assemblies are:

Polyiso = R-21.0 hr∙ft²∙°F/Btu

Lower Layer: 2” polyiso (R-12.0 hr∙ft²∙°F/Btu)

Upper Layer: 1 ½” polyiso (R-9.0 hr∙ft²∙°F/Btu)

Hybrid = R-21.5 hr∙ft²∙°F/Btu

Lower Layer: 2” polyiso (R-12.0 hr∙ft²∙°F/Btu)

Upper Layer: 2 ½” stone wool (R-9.5 hr∙ft²∙°F/Btu)

Stone Wool = R-21.9 hr∙ft²∙°F/Btu

Lower Layer: 2 ½” stone wool (R-9.5 hr∙ft²∙°F/Btu)

Upper Layer: 3 ¼” stone wool (R-12.4 hr∙ft²∙°F/Btu)

The nine roof assemblies created by the three different membrane colours and three

different insulation arrangements were installed on a large roof with relatively few

obstructions located on an industrial building in Chilliwack, within the Lower Mainland of

British Columbia. Each of the roof assemblies covers an area of approximately 150 m².

Figure 1.6 shows the arrangement of the roof assemblies on the building, and Figure 1.7

shows an aerial view of the test roofs.

Figure 1.6 Layout of test roofs on the test building

Polyiso

Hybrid

Stone wool

G-ISO

W-ISO

B-ISO

G-ISO-SW

W-ISO-SW

B-ISO-SW

G-SW

W-SW

B-SW


Figure 1.7 Layout of test roofs on the test building

Figure 1.8 to Figure 1.13 show images of the test roof assemblies being constructed

including installation of the air and vapour barrier, the insulation layers, and the 2-ply SBS

roof membranes. The insulation layers are adhered to the air and vapour barrier and to

each other with a two component polyurethane foam adhesive to limit the movement of the

insulation withen the assemblies. In the case of the roof assemblies with only polyiso

insulation, an asphaltic protection board is also installed to facilitate installation of the roof

membrane, and this projection board is adhered to the upper polyiso layer. In the stone

wool cases, the top surface of the stone wool is impregnated with asphalt and the

membrane is applied directly to this impregnated surface.

Figure 1.8 Installation of the self-adhered air and vapour barrier membrane on the metal roof deck

Figure 1.9 First layer of the polyiso roof being installed on the self-adhered air and vapour barrier membrane and adhered with pulyurethane foam adhesive


Figure 1.10 Stone wool insulation being installed in the stone wool only roof assembly

Figure 1.11 Stone wool insulation being adhered to bottom layer of polyiso insulation using polyurethan foam in the hybrid roof assembly

Figure 1.12 Bottom layer of polyiso insulation, upper layer of stone wool insulation, and base sheet of the 2-ply SBS membrane during construction

Figure 1.13 Completed roofs showing black, white, and grey SBS cap sheet colours

Various sensors were installed within each of the different roof assemblies to measure

indicators of their performance including material temperatures, relative humidity, heat

flux, and dimensional stability of the insulation. The monitoring equipment and sensors

were supplied and installed by SMT Research Ltd. (SMT) under direction of RDH Building

Engineering Ltd. (RDH) and specifications are available through the SMT website

(http://www.smtresearch.ca/). A schematic roof cross-section is provided in Figure 1.14

which illustrates the typical layout of the sensors in each roof assembly and the naming

convention for the sensors installed in the roof assemblies is provided in Table 1.2. When

sensor names do not follow this convention, appropriate sensor name descriptors were

used.

The heat flux sensors were installed between the insulation layers such that they would be

protected from potential wetting (i.e. not at the bottom of the assembly) and from damage

during the torch application of the roof membrane (i.e. not at the bottom of the assembly).

Due to the difference in the thickness of the insulation layers in the different insulation

arrangements, the heat flux sensors were installed at a different depth for the different roof

assemblies. The heat flux sensors were installed under approximately R-9 hr∙°F∙ft²/Btu, R-


9.5 hr∙°F∙ft²/Btu, and R-12.4 hr∙°F∙ft²/Btu of rated R-value for the polyiso, hybrid, and stone

wool roof assemblies respectively. These differences in R-values above the heat flux

sensors may potentially affect the non-steady state heat flux measurements due to the

buffering effect of the insulation; however, under relatively steady state conditions, the

relative depth of the heat flux sensors would have no impact on the measurements.

Figure 1.14 Schematic roof cross-section showing typical arrangement of sensors installed in each roof assembly

TABLE 1.2 SENSOR NAMING CONVENTION

Membrane Colour

- Insulation Arrangement - Sensor Type - Optional

Descriptor

B Black ISO Polyisocyanurate T Temperature Additional descriptors of sensor positioning

G Grey ISO-SW Hybrid (stone wool on top of polyiso)

RH Relative Humidity

W White SW Stone Wool HF Heat Flux

Figure 1.15 to Figure 1.19 show how these sensors were installed in to the roof assemblies

during construction.


Figure 1.15 Monitoring unit located under the metal deck of the roof attached to sensor to measure ambient interior conditions and metal deck temperature

Figure 1.16 Temperature and relative humidity sensor installed on top of the air and vapour barrier prior to installation of the insulation boards

Figure 1.17 Series of three images showing the displacement sensor installed within the stone wool insulation (left), a contact plate being installed on the edge of the insulation to ensure solid contact of the displacement sensor (middle), and a deisplacement sensor and contact plate installed in the insulation such that when the insulation sheets are butted against each other the displacement sensor will touch the contact plate (right)


Figure 1.18 Heat flux sensors are installed between the insulation layers to measure heat flow through the assembly

Figure 1.19 Thermistors installed at the top of the insulation (will be just under the roof membrane once membrane installed) to measure roof membrane temperature

Reflected solar radiation from the roof cap sheets was measured using solar radiation

sensors (pyranometers) mounted approximately 1 m above the roof surface and pointed

downwards as shown in Figure 1.20. Sensors to measure reflected solar radiation were

installed at a high point and low point on the white roof membrane (likely to become less

and more soiled respectively), and also at one location on the roof with a grey cap sheet,

for comparison. The measurements from these sensors can be compared with the

measurements from the solar radiation sensor on the weather station to provide an

indication of in-service reflectance of the roof membranes.

Figure 1.20 Three solar radiation sensors were installed to measure reflected solar radiation from the roof membranes

The exterior conditions were monitored using a weather station located on the building

adjacent to the test roof as shown in Figure 1.21. The weather station includes sensors to

measure ambient temperature, relative humidity, precipitation, wind speed, wind direction,

and total horizontal solar radiation. A camera was also installed to automatically capture

photos of the roof surfaces every hour to allow for study of soiling of the roof membranes.


Figure 1.21 Weather station installed adjacent to test roofs

In some cases the data collection system lost data from the weather station. In these cases

data from the Chilliwack Airport was used to supplement the available monitoring data.

(Environment Canada, 2013)

1.3.3 Energy Modeling

Building energy modeling was performed to assess how the thermal performance of the

roof assemblies, as determined in the laboratory and field testing phases of the study,

affects whole building energy consumption. Additionally, the energy modeling investigates

the optimum roof membrane colour (solar absorptivity) and insulation strategy for

conventional roof assemblies in various North American climates. Simulations were

conducted to compare the same white, grey, and black roof membranes, and the same three

insulation arrangements: polyiso, stone wool, and hybrid.

The building energy modeling was conducted using the U.S. Department of Energy (DOE)

Building Energy Codes Program commercial building prototype model for a stand-alone

retail building designed to meet ASHRAE 90.1-2010 requirements. The building

information files are available online and use the hourly energy modeling program

EnergyPlus. (DOE, 2012) Models were run for one representative city in each of the eight

ASHRAE North American climate zones. A specific goal of the energy modeling was to

investigate the impact of temperature dependant insulation R-values on whole building

energy consumption. This effect is typically not modeled in most whole building simulation

programs, but can be modeled in EnergyPlus.


2 Laboratory Results

The results of the thermal conductivity laboratory testing of the polyiso (fiberglass facer)

and stone wool insulation samples are provided graphically in Figure 2.1 for a range of

mean temperatures. The maximum, minimum, and average performances are shown for

the polyiso samples to provide an indication of the range of performance in the tested

samples. The stone wool did not show the same variation so only the average is provided.

Figure 2.1 Insulation R-value versus mean temperature for polyiso, aged polyiso, and stone wool insulation

Figure 2.1 illustrates that the R-value of polyiso insulation varies more with temperature

than does the R-value of stone wool insulation. Additionally, aged (4-year-old) polyiso has

a significantly reduced R-value as compared to new polyiso at all temperatures, with the

largest difference in R-value being measured at lower mean temperatures. The aging effects

measured in the polyiso insulation are likely as a result of off-gassing of the insulation

product post-manufacturing. Overall, the results of this testing agree well with published

data for polyiso and stone wool from the National Roofing Contractors Association (Graham,

2010; BSC, 2013) Additional testing would be required to determine the thermal

resistances of these insulation types at higher and lower temperatures.

These laboratory measurements can be applied to the insulation assemblies that were

constructed as part of the field monitoring component of this study. Despite having very

similar rated R-values, the insulation in these roof assemblies likely performs significantly

differently due to temperature and aging effects. The graph shown in Figure 2.2

demonstrates how temperature and aging effects would theoretically impact the apparent

R-value of the insulation in each of the assemblies. The mean insulation temperatures for

each of these cases were calculated using an indoor temperature of 21°C.

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

‐10 0 10 20 30 40 50

R‐value per inch

Mean Temperature of Insulation

Polyiso ‐ Maximum

Polyiso ‐ Average

Polyiso ‐ Minimum

Polyiso ‐ Aged (4 years)

Stone Wool ‐ Average


Figure 2.2 Apparent R-values of roof assemblies used in field monitoring calculated based on insulation conductivity testing.

This figure demonstrates the sensitivity of the apparent R-value of the polyiso roof

assemblies to hot and cold temperatures. The R-value (thermal resistance) of the polyiso

roof assemblies decrease significantly at outdoor temperatures either hotter or colder than

approximately 25°C. The lowest R-value within the tested range was determined at a high

exterior surface temperature of approximately -10°C. At this temperature the R-value was

determined to be approximately 4.8 hr∙ft²∙°F/Btu less than the R-value of this assembly at

25°C, which is approximately at 22% decrease. Temperature of the roof membrane was

measured as part of the field monitoring component of this study and is discussed further

in Section 3.

The polyiso roof also shows significantly reduced apparent R-values due to aging effects.

The 4-year-old polyiso insulation ranges from approximately 9 to 18% less than the un-aged

insulation.

The stone wool insulation assembly also demonstrates temperature dependence; however

the effect is significantly less pronounced than that of the polyiso. Additionally, the R-value

of this assembly does not decrease at both warmer and colder mean temperatures, and

instead actually increases as the mean temperature decreases. The maximum decrease in

the apparent R-value of the stone wool assembly is also at the highest surface temperature

for which conductivities were measured, 60°C. The R-value of the assembly at this

temperature is approximately R-1.0 hr∙ft²∙°F/Btu (5%) lower than the R-value at 25°C (R-21.2

hr∙ft²∙°F/Btu). The R-value at a mean temperature of -10°C is approximately R-1.0

hr∙ft²∙°F/Btu higher than the R-value at 25°C.

The hybrid roof assembly provides a combination of the effects noted for the polyiso and

stone wool roof assemblies. The stone wool insulation buffers the temperatures

experienced by the underlying polyiso consequently allowing the polyiso to operate closer

to its optimum temperature range. This assembly has very similar temperature response

to the stone wool assembly except for at temperatures below 10°C where slightly lower R-

values were determined. The decrease in R-value of the roof assembly due to polyiso aging

effects is also somewhat mitigated by the hybrid roof assembly. While the polyiso insulation

still decreases in R-value, in this assembly it only provides approximately 55% of the rated

R-value, and thus the decrease in apparent R-value is significantly less in this hybrid

assembly that in the polyiso assembly.

14

15

16

17

18

19

20

21

22

23

24

‐10 0 10 20 30 40 50 60

Effective Assembly R‐value

Outdoor Membrane Surface Temperature (Indoor, 21oC)

Stone Wool (Initial or Aged)

Hybrid (Initial Average)

Hybrid (Aged)

Polyiso (Initial Average)

Polyiso (Aged)


Overall, the R-value of the polyiso was determined to be significantly more sensitive to aging

and temperature affects than is the stone wool insulation. As a result, roofs using

exclusively polyiso insulation may provide significantly less thermal resistance in-service at

temperature extremes (hot or cold) than is indicated by its rated R-value.


3 Field Monitoring Results

This study assesses the effect of two different parameters affecting conventional roof

assembly performance: the cap sheet colour (reflectance), and the insulation arrangements.

These factors are addressed separately in the subsequent sections so that their affects can

be determined independently. To facilitate this independent analysis this results section

has been subdivided into four main sections with subsections:

Overview of Boundary Conditions

Thermal Performance – Membrane Cap Sheet Colour

Membrane In-Service Reflectance

Membrane Temperature

Heat Flux

Interior Metal Deck Temperature

Thermal Performance – Insulation Arrangement

Heat Flux

Membrane Temperature

Interior Metal Deck Temperature

Dimensional Stability of Insulation

Long-term Displacement

Short-term Displacement

In some cases data is not available due to intermittent malfunctioning of the installed

monitoring equipment, but these instances do not significantly affect the findings and are

discussed where appropriate. Annual data in this report is typically presented from May

2013 to April 2014 as this is when the data collection was most consistent. Graphs provided

in this section of the report are supplemented with additional graphs provided in Appendix

A.

3.1 Overview of Boundary Conditions

The test roof assemblies were located in Chilliwack, British Columbia which is located within

the Lower Mainland region surrounding Vancouver. The roofs were monitored from

September 2012 to June 2014, and data is typically presented from May 2013 to April 2014

because data collection was most consistent during this period.

Graphs providing the average exterior and interior conditions for each month are provided

the following figures. The average exterior monthly temperature, exterior dew point

temperature, and interior temperature are provided in Figure 3.1. Monthly heating degree

days (HDD), and cooling degree days (CDD) are provided in Figure 3.2. The average monthly

relative humidity and total daily solar radiation are provide in Figure 3.3 and Figure 3.4

respectively. Figure 3.5 provides the distribution of wind direction and speed during this

period.


Figure 3.1 Graph of monthly average temperature and dew point temperature during the main monitoring period from May 2013 to April 2014

Figure 3.2 Graph of monthly average HDD (18°C, 64°F) and CDD (10°C, 50°F) during the main monitoring period from May 2013 to April 2014

Figure 3.3 Graph of monthly average relative humidity during the main monitoring period from May 2013 to April 2014

14

23

32

41

50

59

68

77

‐10

‐5

0

5

10

15

20

25

May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr

Temperature [°F]

Temperature [°C]

Exterior Temperature Exterior Dew Point Temperature Interior Temperature

0

180

360

540

720

900

1080

0

100

200

300

400

500

600


Degree Days [°F∙days]

Degree Days [°C∙days]

HDD (18°C, 64°F) CDD (10°C, 50°F)

0

10

20

30

40

50

60

70

80

90

100


Relative

Humidity [%

]

Relative Humidity


Figure 3.4 Graph of monthly average total daily solar radiation during the main monitoring period from May 2013 to April 2014

Figure 3.5 Wind rose indicating the average wind speed and frequency of wind for each direction during the main monitoring period from May 2013 to April 2014

3.2 Thermal Performance - Membrane Cap Sheet Colour

The field monitoring component of this study evaluated the performance of white (W), grey

(G), and black (B) membrane cap sheets. The colour of these membranes primarily affects

their solar reflectance. The subsequent sections assess the in-service solar reflectance of

the membranes and the impact on membrane temperatures, interior metal deck

temperatures, and heat flux through the assemblies. Supplementary graphs are provided

in Appendix A.

3.2.1 Membrane In-Service Reflectance

The different membrane cap sheet colours have different rated solar reflectance values as

previously provided in Table 1.1. As part of this study, the total horizontal solar radiation

from the sun was measured as well as the reflected solar radiation from the white (at a high

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May

Total D

aily Horizontal Solar Rad

iation

[Whr/m²]

Total Daily Solar Radiation

0

1

2

3

4N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

Average Wind Speed [m/s]

Frequency [%/4]Average Wind Speed = 1.4 m/s


and a low point on the roof surface) and grey roofs to determine their in-service solar

reflectance. This testing was not performed in accordance with ASTM reflectance

measurements and instead provides a relative measurement intended to facilitate

comparison of the roof membranes. Figure 3.6 shows these measurements for a period

from June 2nd to 8th, 2013 to demonstrate the difference in in-service roof reflectance.

Note that the results for the two white roofs are nearly identical and so overlap almost

exactly on the graph.

Figure 3.6 Graph of total solar radiation and reflected radiation from the roof surface from June 2 to 8, 2013

The preceding figure indicates that for the given period from June 2nd to June 8th, 2013,

approximately 51% of the incident solar radiation is reflected by the white roof (both

locations), and 27% by the grey roof. The white roof and the grey roof have manufacturer

rated solar reflectance values of 58% and 14% respectively, and the difference between these

values and the field measured values is expected due to the difference in measuring

techniques. The technique used in this study is intended to provide a relative measure of

reflectance to allow for comparison of the roofs in the study, but is not intended to provide

a measurement of the actual reflectance of the membranes as would be consistent with the

manufacturer rating. While the in-service reflectance of the white roof was similar to this

rated value, the grey roof reflected significantly more solar radiation in-service. This is

potentially because the reflected solar radiation sensor on the grey roof is located relatively

close to the white roof and may have been measuring some reflected radiation from the

white roof or other adjacent surfaces.

Typically the measured reflectance values were lowest in the summer and highest in the

winter as shown on a monthly average basis in Figure 3.7. During the winter months there

is less direct solar radiation due to cloud cover and consequently diffuse solar radiation is

a larger proportion of the total solar radiation incident on the roof surface. This diffuse

radiation also has a slightly different spectrum than does direct solar radiation. The

reflectance of the roof membrane was measured for the solar spectrum, so the roof

membranes likely have a different reflectance with respect to this diffuse radiation which

may be the cause of the observed seasonal variation in the measured reflectance. It is also

possible that the diffuse radiation is more likely to irradiate the roof and sensor equally and

consequently that a larger proportion of the solar radiation measured by the sensor is not

reflected from the roof which leads to a higher measured reflectance that is not indicative

of the actual reflectance of the roof. The increased measured reflectance in the winter could

0

200

400

600

800

1000

1200

Jun 2 Jun 3 Jun 4 Jun 5 Jun 6 Jun 7 Jun 8

Solar Rad

iation [W/m

²]

Solar Radiation

Reflected Solar ‐ White (High)

Reflected Solar ‐ White (Low)

Reflected Solar ‐ Grey

Average Incident SolarRadiation Reflected

White (High) = 51%

White (Low) = 51%

Grey = 27%


also be caused by increased moisture on the surface of the roof (water and ice) during the

winter periods due to more precipitation and colder temperatures.

The annual average reflectance shows good correlation between the measured reflectance

of the white membrane and the values provided by the manufacturer. The measurement of

the reflectance of the white membrane at a low point is slightly lower than that of the

membrane at a high point which is likely due to the low point being more likely to collect

dirt and becoming soiled more quickly than the high point. The grey membrane reflectance

is significantly higher than the rated value and is likely due to placement of the sensor near

to the white roofs as discussed earlier with respect to Figure 3.6.

Figure 3.7 Chart of average monthly measured cap sheet membrane reflectances

As noticeable in the reflectance measurements of the two white membrane locations, the

in-service solar reflectance of the roof membrane will be affected by soiling which can

potentially decrease the reflectance of the roof, particularly of the white roof. The effects

of soiling on roof membrane reflectance have previously been studied by Koshiishi et al

(2014) who found a significant reduction in the reflectance of reflective (i.e. white) roof

membranes over the first year of exposure, and limited reductions thereafter. To

qualitatively assess roof membrane soiling for the test roofs in this study, a camera was

installed to periodically take pictures of each of the roofs. Figure 3.8 provides images of

the roof when it was newly installed. Figure 3.9 and Figure 3.10 provide images the roof

after approximately 7 months of service (March 15, 2013) and after approximately 13

months of service (October 21, 2013).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual Rated

Reflectan

ce

White (high) White (low) Grey

*

*Rated reflectance was measured using a different method than was used in the field study.


Figure 3.8 Set of three images documenting the condition of the roof membranes shortly after insatllation on August 21, 2012

Figure 3.9 Set of three images documenting the condition of the roof membranes on March 15, 2013 approximately 7 months after installation.

Figure 3.10 Set of three images documenting the condition of the roof membranes on October 21, 2013 approximately 14 months after installation.

These images illustrate that there is significant soiling of the roof membrane in close

proximity to the roof drains, but that in general the roof membranes have not become

significantly visually soiled over the course of approximately a year of service.

Consequently, the reflectance of these roofs has not likely changed significantly since they

were installed. Figure 3.11 provides a chart of average seasonal reflectance of the three

roofs to facilitate comparison of reflectance in Winter 2013 to reflectance in Winter 2014.


Figure 3.11 Chart of seasonal average and annual average (Spring 2013 to Winter 2014) reflectance of roof membranes

This comparison indicates that soiling of the roof membranes has had a small effect on the

white membrane located at a low point on the roof. The limited soiling that is observed

on these test roof may in part be due to the relatively unpolluted atmospheric conditions in

the vicinity of the test building. The test roofs are located in rural semi-industrial area as

shown in Figure 3.12, and airborne particulates are typically found in relatively low

quantities in rural areas as compared to urban centres.

Figure 3.12 Aerial image showing terrain surround the test roof location

There is also limited vegetation in close proximity to the test roofs so leaves and other

debris from vegetation does not typically fall on the test roofs and the absence of this debris

source could also be contributing to the lack of soiling which was observed.

Despite the limited soiling observed to this point, future years of service and associated

continued soiling may gradually degrade the reflectance of the roof membranes, and in

particular of the white roof membrane. Continued monitoring of these membranes would

allow for the evaluation of long-term soiling effects.

After soiling, it may be possible to restore these membranes to their initial reflectance by

cleaning the membrane or recoating. Both Akbari et al (2005) and Koshiishi et al (2014)

found that for most roofs cleaning of the roof membrane using water and wiping

(simulating annual rain) was sufficient to restore the roof membrane reflectance to near its

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Winter2013

Spring2013

Summer2013

Fall2013

Winter2014

Annual

Reflectan

ce

White (high) White (low) Grey


initial value, but that for membranes with “deep irregularities” (Koshiishi et al, 2014) (such

as those created by granules on SBS cap sheets) or algae growth, additional cleaning

measures are required. Further monitoring and research would be required to evaluate the

long-term impact of soiling of these roof membranes, and the effectiveness of roof cleaning

methods.

3.2.2 Membrane Temperature

It is generally understood within the roof industry that roof membrane temperatures are

largely dependent on absorption of solar radiation; consequently, roof temperatures are

often significantly warmer than ambient air temperatures and largely dependent on roof

membrane reflectance (i.e. colour). The increased solar reflectance of the white membrane

relative to the grey membrane and of the grey membrane relative to black membrane means

that less solar energy is absorbed by these membranes. This difference in the amount of

absorbed radiation causes significant differences in the roof membrane temperatures.

Figure 3.13 to Figure 3.15 provide graphs of the roof membrane temperatures from June

2nd to June 8th, 2013 grouped by insulation type to allow for evaluation of the effect of

membrane reflectance (i.e. colour) on membrane temperature. The effect of membrane

reflectance is most noticeable during sunny summer periods when, in the climate of Lower

Mainland British Columbia where the study was conducted, there is typically more direct

solar radiation. For this reason, the figures provided in this section are primarily during

sunny summer periods, though increased roof temperatures compared to the ambient

exterior temperature are noticeable throughout the year.

Figure 3.13 Graph of roof membrane cap sheet temperature for the three polyiso roof assemblies from June 2 to 8, 2013

32

50

68

86

104

122

140

158

176

0

10

20

30

40

50

60

70

80


Temperature [°C]

p p

W‐ISO T‐CAP

G‐ISO T‐CAP

B‐ISO T‐CAP

Ambient Exterior

Temperatu

re [°F]


Figure 3.14 Graph of roof membrane cap sheet temperature for the three hybrid roof assemblies from June 2 to 8, 2013

Figure 3.15 Graph of roof membrane cap sheet temperature for the three stone wool roof assemblies from June 2 to 8, 2013

These figures show that maximum roof temperatures are significantly reduced for the more

reflective white roofs than for the other roofs and the temperatures also change more slowly

for the white roofs than for the grey and black roofs. The grey roof also experienced

reduced maximum temperatures and rates of temperature change relative to the black

roofs; however, as one would expect, this effect is not as significant as for the white roofs.

The impact of roof membrane colour on roof membrane temperatures is most significant

during sunny and warm periods when roof membrane temperatures reach their annual

maximums; however, it is noticeable year-round. To illustrate the annual variation in the

impact of membrane colour on peak roof membrane temperatures, the monthly average

daily maximum temperatures and the maximum membrane temperature for each month

are graphed in Figure 3.16. The decreases in maximum membrane temperature of the

white and grey roofs relative to the black roofs are shown in Figure 3.17.

32

50

68

86

104

122

140

158

176

0

10

20

30

40

50

60

70

80


Temperature [°C]

W‐ISO‐SW T‐CAP

G‐ISO‐SW T‐CAP

B‐ISO‐SW T‐CAP

Ambient Exterior

Temperatu

re [°F]

32

50

68

86

104

122

140

158

176

0

10

20

30

40

50

60

70

80


Temperature [°C]

W‐SW T‐CAP

G‐SW T‐CAP

B‐SW T‐CAP

Ambient Exterior

Temperatu

re [°F]


Figure 3.16 Chart of monthly average of the maximum daily membrane temperatures an maximum membrane temperature for each month for the white, grey, and black roofs, averaged for the different insulation arrangements

Figure 3.17 Chart of monthly average reduction in maximum daily membrane temperatures for the roofs with white and grey membrane cap sheets as compared to the roofs with black membrane cap sheets

The effect of membrane colour on the maximum roof membrane temperature can also be

assessed for the different insulation arrangements. Figure 3.18 shows the monthly average

reduction in maximum membrane temperature for the white roofs compared to the black

roof for all of the roofs with white membrane cap sheets. This figure indicates that typically

the reduction in daily maximum membrane temperature created by the use of a more

reflective membrane is largest for the polyiso roof assemblies, though the cause of this

effect is unknown.

32

50

68

86

104

122

140

158

176

194

0

10

20

30

40

50

60

70

80

90


Temperature [°F]

Temperature [°C]

White Grey Black White ‐ Maximum Grey ‐ Maximum Black ‐ Maximum

* *

*W‐ISO‐SW had significant data loss in August and September and is removed from the average for those months.

0

9

18

27

36

45

0

5

10

15

20

25

May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual

Decrease in

Temperature [°F]

Decrease in

Temperature [°C]

White Grey

* *



Figure 3.18 Chart of monthly average reduction in maximum daily membrane temperatures for the roofs with white membrane cap sheets as compared to the roofs with the same insulation arrangements and black membrane cap sheets

While more reflective roof membranes were found to reduce the maximum membrane

temperature and consequently to likely extend the service life of the roof membrane, there

was no noticeable effect of roof membrane colour on the minimum night-time

temperatures. This finding is likely because while night sky radiation can frequently cause

roofs to cool below ambient outdoor temperatures, this radiation is primarily in the infrared

spectrum (not solar spectrum) and consequently the infrared (i.e. thermal) absorption and

emittance of the membranes are of most importance. As shown previously in Table 1.1,

the thermal emittances (and consequently absorptance) of the three tested membranes are

very similar, and consequently the reduction in temperature due to night sky radiation

would be expected to be similar for all of the tested membrane colours.

3.2.3 Membrane Degradation

The degradation of roof membranes often occurs as the result of chemical reactions and

most chemical reactions happen faster at higher temperatures. In many cases the

relationship between temperature and reaction rate is described using the Arrhenius

equation as shown in Equation 3-1.

∙ ∙ Equation 3-1

k = Reaction Rate Constant [units vary]

C1 = Constant Depending on the Reaction [units vary]

Ea = Activation Energy [J/mol]

R = Universal Gas Constant [8.314 J/mol∙K]

T = Absolute Temperature [K]


0

5

10

15

20

25


Decrease in

Temperature [°C]

Monthly Average Decrease in Daily Maximum Membrane Temperature Compared to Black for White Membrane

W‐ISO W‐ISO‐SW W‐SW

* *


Importantly this equation indicates that for a given increase in temperature, the increase in

the reaction rate can be significantly greater. A rule of thumb is that the increase in the

oxidation rate of roof membranes roughly doubles for every 10°C increase in temperature.

(Docent n.d.) Using this rule of thumb and Equation 3-1, the relative rate of reaction, and

consequently of membrane degradation, was calculated over a range of membrane

temperatures and graphed in Figure 3.19. The degradation rate was set at 1 for a

temperature of 20°C and all other reaction rates are relative to the rate at this temperature.

Figure 3.19 Graph of reaction rate relative to reaction rate at 20°C versus temperature assuming that reaction rate doubles from 20°C to 30°C

Using the relationship shown in Figure 3.19, the relative degradation rates of the roof

membrane cap sheets were determined and are plotted in Figure 3.20, Figure 3.21, and

Figure 3.22 for the polyiso, hybrid, and stone wool roof assemblies respectively. These

figures show a similar relationship to the membrane temperature graphs provided earlier

(Figure 3.13 to Figure 3.15), but the difference in degradation rate is exaggerated compared

to the difference in temperature due to the governing Arrhenius equation. Consequently,

a relatively small reduction in the maximum membrane temperature as a result of the use

of a more reflective roof membrane could potentially significantly extend the service life of

the membrane. For example, during the maximum temperature on June 4th, 2013 the black

polyiso roof was calculated to be aging due to chemical reactions approximately 12 times

faster than the white roof.

Figure 3.20 Graph of relative degradation due to chemical reactions assuming the Arrhenius equation describes relationship of reaction rate to temperature for polyiso roofs

0

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100

150

200

250

300

350

400

450

500

‐20 ‐10 0 10 20 30 40 50 60 70 80 90 100

Reaction Rate Relative to Rate at 20°C

Temperature [°C]

0

20

40

60

80

100

120

140

160

180



W‐ISO

G‐ISO

B‐ISO

Ambient Exterior

x12

x5.5


Figure 3.21 Graph of relative degradation due to chemical reactions assuming the Arrhenius equation describes relationship of reaction rate to temperature for hybrid roofs

Figure 3.22 Graph of relative degradation due to chemical reactions assuming the Arrhenius equation describes relationship of reaction rate to temperature for stone wool roofs

To examine the relative amounts of degradation that the roof membranes undergo as a

result of the differences in temperatures created by the white, grey, and black roof

membrane colours, the cumulative degradation (degradation integrated over the operating

time period) for each of the roof assemblies was calculated and are plotted in Figure 3.23.

The amount of relative degradation was only summed for hours in which all roof

membranes had data to avoid a misleading comparison due to one roof having more or less

data than another.

0

20

40

60

80

100

120

140

160

180



W‐ISO‐SW

G‐ISO‐SW

B‐ISO‐SW

Ambient Exterior

0

20

40

60

80

100

120

140

160

180


Reaction Rate Relative

to Rate at 20°C

W‐SW

G‐SW

B‐SW

Ambient Exterior

x11x6

x9 x5


Figure 3.23 Graph of cumulative relative degradation due to chemical reactions assuming Arrhenius equation describes relationship of reaction rate to temperature

This figures clearly illustrates the decrease in membrane degradation due to chemical

reactions as a result of the use of a reflective membrane. For example, according to the

Arrhenius equation, the white roof membrane and the grey roof membrane on polyiso

underwent approximately 5 times and 3 times less aging due to chemical reactions than

did the black membrane on polyiso for the same one year period. Consequently, the use

of more reflective roof membranes can potentially significantly extended roof membrane

service-life. There is also a noticeable difference in the calculated weathering for the

different insulation arrangements with black membrane; however, this difference is small

compared to the difference created by membrane colour.

This extension of service-life of the roof membrane does not account for the potential

additional benefits associated with more reflective roof membranes moderating membrane

temperatures including less thermal expansion and contraction. That said, it is likely that

in-service roof membrane service-life would not be extended by the same amount as

indicated by these results because of weathering of the roof membranes by other factors.

Overall, the reduction of both temperature magnitude and rate of temperature change

caused by the increased reflectance of the white and grey membranes is likely to improve

roof membrane durability and extend the roof service-life by: reducing the maximum strain

magnitudes and rates on the roof membrane caused by thermal expansion and contraction;

reducing the rate of deleterious chemical reactions; and by reducing the loss of volatile

membrane constituents. This effect is likely to be more pronounced in the white membrane

than the grey as it is more reflective and consequently experiences lower peak temperatures

and slower rates of temperature change than does the grey membrane.

Further research and testing could be performed in a few years to confirm and evaluate the

effect of this calculated increased aging rate on the membrane performance. This work

could include testing of the physical properties of the membrane including evaluation of

the stress-strain relationship of the membrane samples.

3.2.4 Urban Heat Island

Reduced membrane temperatures can also have positive implications with respect to urban

heat island effect. Urban heat island is an affect by which the more solar absorptive roofs,

walls, and pavement of urban areas increases in heat more relative to the surface in rural

areas and consequently causes the average temperature in urban areas to be higher than

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May

Relative

Degradation

W‐ISO

W‐ISO‐SW

W‐SW

G‐ISO

G‐ISO‐SW

G‐SW

B‐ISO

B‐ISO‐SW

B‐SW

x5

x3


in rural areas. It is also attributed to less evapotransporative cooling and less efficient

transport of heat energy by convection. (Hewitt et al., 2014; Zhao et al, 2014) Increased

temperatures, in particular in urban areas, have been correlated with health issues, and

increased peak electricity use. Reflective roofs have been found to reduce summertime air

temperatures of the surrounding area by approximately 1 to 2°C. (Sproul et al, 2014; Akbari

et al, 2005) Large scale evaluation of the urban heat island implications of reflective roof

membranes is beyond the scope of this study.

3.2.5 Heat Flux

The difference in roof membrane temperatures as a result of roof membrane reflectance

also affects the heat flux through the roof assembly. The measured heat flux through the

polyiso roof assemblies during the same period from June 2nd to 8th, 2013 is shown in

Figure 3.24. Note that in this figure and all subsequent heat flux graphs, positive heat flux

is heat flow out of the building and negative heat flux is heat flow in to the building.

Figure 3.24 Graph of heat flux through the three polyiso roofs from June 2 to 8, 2013

The effect of roof membrane reflectance (i.e. colour) on the net heat flux into or out of the

building through the roof assembly is also apparent on an annual basis. Figure 3.25

provides monthly average heat flux out of the building through the roof (outward heat flow

is positive) from May 2013 to April 2014.

‐25

‐20

‐15

‐10

‐5

0

5

10


Heat Flux [W

/m²]

Heat Flux Sensors

W‐ISO HF

G‐ISO HF

B‐ISO HF

Outw

ardHeat Flo

wInward

Heat Flo

w


Figure 3.25 Chart of monthly average daily heat flow through the roof assemblies averaged for each roof membrane colour

It is apparent from this figure that the black roofs on average transfer more heat in to the

building during relatively warm periods of the year than do the white and grey roofs. The

heat transfer out through roofs during the colder months is slightly higher for the black

roofs, but this difference is less significant than the difference during warm periods.

Important to note from this figure is that over the course of the year there is more heat gain

in to the building through the roofs than there is heat loss. This was initially a surprising

finding given that the test roofs are located in a heating dominated climate (ASHRAE Climate

Zone 5).

The difference in heat flux caused by the difference in reflectance of the roof membranes

likely has implications with respect to building energy consumption. This potential impact

is analysed in Section 4.

3.2.6 Interior Metal Deck Temperature

The interior metal deck temperature influences the thermal comfort of building occupants

as it composes part of the mean radiant temperature for the interior space. The

temperature of the metal deck is potentially impacted by the roof membrane colour, and to

examine this potential impact the interior metal deck surface temperatures were plotted for

a warm day, June 30th, 2013, in Figure 3.26, Figure 3.27, and Figure 3.28 for the polyiso,

hybrid, and stone wool roof assemblies respectively. It is important to note that interior

metal deck temperatures are also significantly impacted by interior temperature

fluctuations and given that the test roofs are installed on a manufacturing facility,

fluctuations in interior temperature due to manufacturing operations could potentially

impact the measured interior metal deck temperatures; however, this was not noted to be

a significant factor. The average monthly interior temperatures were provided in Section

3.1.

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Tran

sfer [W

∙hr/m² per day]

White Grey Black

Outw

ardHeat Flo

wInward

Heat Flo

w


Figure 3.26 Graph of interior metal deck temperature on June 30th, 2013 for the polyiso roof assemblies

Figure 3.27 Graph of interior metal deck temperature on June 30th, 2013 for the hybrid roof assemblies

Figure 3.28 Graph of interior metal deck temperature on June 30th, 2013 for the stone wool roof assemblies

The preceding figures indicate that typically the interior metal deck temperature is more

stable (less extreme minimum and maximum temperatures) for the white roofs than for the

23

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25

26

27

28

29

30

31

32

33

34

35

36

37

Jun 30 00:00 Jun 30 06:00 Jun 30 12:00 Jun 30 18:00 Jul 1 00:00

Temperature [°C]

W‐ISO TEMP‐DECK

G‐ISO TEMP‐DECK

B‐ISO TEMP‐DECK

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37


Tem

perature [°C]

W‐ISO‐SW TEMP‐DECK

G‐ISO‐SW TEMP‐DECK

B‐ISO‐SW TEMP‐DECK

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37


Temperature [°C]

W‐SW TEMP‐DECK

G‐SW TEMP‐DECK

B‐SW TEMP‐DECK


grey roofs, and more stable for the grey roofs than for the black roofs. This improved

stability for the more reflective roofs would likely result in improved thermal comfort for

the building occupants as the metal deck temperature stays closer to the ambient interior

air temperature. The differences in metal deck temperatures based on insulation

arrangement are discussed in later sections of this report.

3.3 Thermal Performance - Insulation Arrangement

The field monitoring evaluated the performance of three different insulation arrangements:

polyisocyanurate (polyiso or ISO), stone wool (SW), and a hybrid (ISO-SW) assembly with a

lower layer of polyiso and an upper layer of stone wool. As discussed in Section 2,

laboratory testing indicates that the R-value of these insulation arrangements vary with

temperature, and in particular that the polyiso insulation becomes significantly less

insolative at both high and low temperatures. The field monitoring of these different

assemblies analyses the impact of this varying R-value on the performance of the roof

assemblies. The impact of the difference in thermal mass between the assemblies and of

potential latent heat transfer are also assessed.

Supplementary graphs are provided in Appendix A.

3.3.1 Heat Flux

To assess the impact of the insulation arrangement on the heat flux through the roof

assemblies, the heat flux measurements have been averaged on a monthly basis for each

insulation arrangement and are provided in Figure 3.29. The heat flux measurements for

each of the roof insulation arrangements are presented separately in Appendix A.

Figure 3.29 Chart of monthly average daily heat flow through the roof assemblies averaged for each insulation arrangement

The monitoring results presented in Figure 3.29 indicate that on average the heat flow both

in to and out of the building through the roof assembly is of largest magnitude for the

polyiso (ISO) insulation arrangement, followed by the hybrid (ISO-SW) insulation

arrangement, and then the stone wool (SW) insulation arrangement. This finding is in

0

100

200

300

400

500

600

‐150

‐100

‐50

0

50

100


Degree Days [°C∙days]

Daily Energy Tran

sfer [W∙hr/m² per day]

ISO ISO‐SW SW Heating Degree Days (18°C)

Outw

ardHeat Flow

InwardHeat Flow


contrast to the similar rated R-value of the three different roof assembly insulation

arrangements and indicates that heat flow through the roof assemblies is impacted by the

apparent in-service thermal performance of the insulation which is consistent with the

laboratory measurements of insulation conductivity presented in Section 1.3.1. In other

words, despite the similar rated R-values of these roof assemblies, the polyiso roof

assemblies allow noticeably more heat flow through the assembly than do the stone wool

insulation assemblies for the same rated R-value. The whole building energy consumption

implications of this finding are assessed in Section 4.

Theoretically it is possible to determine in-service R-values of each assembly based on a

measurement of the heat flux through the insulation and of the temperature difference

across the insulation; however, it was not possible to determine consistent in-service R-

values using this method due to a combination of factors including in particular the non-

steady state nature of the exterior conditions created in part by solar heat gains and night

sky cooling effects.

3.3.2 Membrane Temperature

The different characteristics of the insulation arrangements may have an impact on

membrane cap sheet temperatures. To evaluate this potential impact, the cap sheet

temperatures for each of the white, grey, and black roof assemblies are graphed in Figure

3.30, Figure 3.31, and Figure 3.32 respectively.

Figure 3.30 Graph of roof membrane temperatures for roof assemblies with a white cap sheet on June 30, 2013

32

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158

176

194

0

10

20

30

40

50

60

70

80

90


Temperature [°C]

W‐ISO T‐CAP

W‐ISO‐SW T‐CAP

W‐SW T‐CAP

Ambient Exterior

Temperatu

re [°F]

56°C at 13:00

55°C at 13:0055°C at 15:00


Figure 3.31 Graph of roof membrane temperatures for roof assemblies with a grey cap sheet on June 30, 2013

Figure 3.32 Graph of roof membrane temperatures for roof assemblies with a black cap sheet on June 30, 2013

Each of the preceding figures clearly indicates a lag of approximately 1 to 2 hours in the

membrane cap sheet temperature for the hybrid (ISO-SW) assemblies as compared to both

the polyiso (ISO) and the stone wool (SW) assemblies. While figures illustrating this affect

are only provided for June 30th, 2013, the affect is consistently noticeable during the

monitoring period. In addition to this lag, there is also a noticeable reduction in the daily

maximum membrane temperature for the hybrid roof assemblies as compared to the other

two assembly types. There are a number of possible explanation for this lag and reduction

in peak temperatures including temperature dependent R-values, and potentially also

thermal mass and latent heat transfer affects (Hedline, 1988; Hedlin, 1987).

The minimum daily temperature of the roof membranes was also assessed for the different

insulation arrangements. Figure 3.33 shows the monthly average minimum daily

temperature for each of the insulation arrangements and clearly demonstrates that polyiso

insulation roof typically has the coldest temperatures, followed by the stone wool insulation

and hybrid insulation assemblies. This finding likely indicates either less heat loss through

the polyiso insulation compared to the hybrid or stone wool under these conditions, or

consistently less heat gain for these assemblies. Neither of these potential causes is

32

50

68

86

104

122

140

158

176

194

0

10

20

30

40

50

60

70

80

90


Temperature [°C]

G‐ISO T‐CAP

G‐ISO‐SW T‐CAP

G‐SW T‐CAP

Ambient Exterior

Temperatu

re [°F]

74°C at 14:00 73°C at 14:00

71°C at 14:00

32

50

68

86

104

122

140

158

176

194

0

10

20

30

40

50

60

70

80

90


Temperature [°C]

B‐ISO T‐CAP

B‐ISO‐SW T‐CAP

B‐SW T‐CAP

Ambient Exterior

Temperatu

re [°F]

84°C at 13:00

81°C at 13:0080°C at 14:00


consistent with the other findings presented in this report. Further research is required to

determine the cause of this finding.

Figure 3.33 Graph of monthly average minimum daily roof membrane temperatures

3.3.3 Interior Metal Deck Temperature

As discussed with respect to roof membrane colour, the interior metal deck temperature

influences the thermal comfort of building occupants. The metal deck temperature is

potentially affected by the roof insulation arrangement, and to examine this potential effect

the interior metal deck surface temperatures were plotted for a warm day, June 30th, 2013,

for the black, grey, and white roof assemblies respectively.

Figure 3.34 Graph of interior metal deck temperature on June 30th, 2013 for the white roof assemblies

23

32

41

50

59

‐5

0

5

10

15


Temperature [°F]

Temperature [°C]

ISO ISO‐SW SW

* *


68

77

86

95

104

20

25

30

35

40


Temperature [°F]

Temperature [°C]

W‐ISO TEMP‐DECK

W‐ISO‐SW TEMP‐DECK

W‐SW TEMP‐DECK

33°C at 19:0033°C at 17:00

32°C at 19:00


Figure 3.35 Graph of interior metal deck temperature on June 30th, 2013 for the grey roof assemblies

Figure 3.36 Graph of interior metal deck temperature on June 30th, 2013 for the black roof assemblies

The preceding figures indicate that similarly to the roof membrane temperatures, there is

a lag in the maximum metal deck temperature experienced by the hybrid roof assemblies

as compared to the polyiso roof assembly. There is also a lag in the temperature of the

hybrid roof assemblies, which is less than the lag for the stone wool assemblies for the

white and grey roofs, but more for the black roofs. The cause of this discrepancy is

unknown. Overall, the hybrid roof provides the most stable interior metal deck temperature

for the white and grey roofs, and the stone wool insulation provides the most stable metal

deck temperature for the black roofs. These more stable temperatures would likely result

in improved thermal comfort for the building occupants.

Further research is required to determine the optimal hybrid insulation split between

polyiso and stone wool insulation.

3.3.4 Insulation Thermal Mass

Lags and associated reductions in peak temperatures are commonly created by thermal

mass affects which moderate temperature changes by absorbing and releasing relatively

large amount of thermal energy for a given change in temperature. (Siplast, 2010) In these

68

77

86

95

104

20

25

30

35

40


Temperature [°F]

Temperature [°C]

G‐ISO TEMP‐DECK

G‐ISO‐SW TEMP‐DECK

G‐SW TEMP‐DECK

35°C at 17:00

34°C at 19:00

32°C at 18:00

68

77

86

95

104

20

25

30

35

40


Temperature [°F]

Temperature [°C]

B‐ISO TEMP‐DECK

B‐ISO‐SW TEMP‐DECK

B‐SW TEMP‐DECK

36°C at 17:00

34°C at 19:00

35°C at 18:00


roof assemblies the thermal mass most directly connected to the roof membrane is the

insulation. The approximate density, specific heat capacity, volumetric heat capacity, and

thermal diffusivity for the polyiso, stone wool, and SBS membrane products used in the test

roofs are provided in Table 3.1.

TABLE 3.1 INSULATION PROPERTIES RELEVANT TO THERMAL MASS

Insulation Type Density [kg/m³]

Specific Heat Capacity [J/kg∙K]

Volumetric Heat

Capacity [kJ/m³∙K]

Thermal Diffusivity [m²/s 10-7]

Polyiso 32 1500 48 3.3

Stone Wool 176 800 141 2.4

SBS Membrane 1250 1510 1882 47.8

These values were then used to calculate the thermal mass of the insulation per square

meter of roof area for each of the insulation arrangements. The thermal mass of each of

the roof assemblies per square meter of roof area were determined to be 4.6, 11.4, and

20.6 kJ/m²•K for the polyiso, hybrid, and stone wool roof assemblies respectively which is

in addition to approximately 12.2 kJ/m² provided by the SBS roof membrane. These values

clearly illustrate that there is significantly more thermal mass in the assemblies which

include stone wool than in the assemblies with only polyiso; however, there is more thermal

mass in the only stone wool assembly than in the hybrid assembly, so the thermal mass

affect does not fully explain the measured membrane temperatures.

3.3.5 Latent Heat Transfer

Another potential cause of the lag in the roof membrane and metal deck temperatures is

latent heat transfer within the assembly. Latent heat transfer is the movement of energy as

a result of the movement of moisture within the assembly. (Hedlin, 1988; Hedlin, 1987)

In these roof assemblies the heating during the day and cooling at night of the roof

membrane creates the potential for cyclically driving moisture inward and then outward

over the course of each day. This cyclical moisture movement could potentially transfer

significant amounts of energy through the roof assembly and influence the membrane

temperatures. Evaporation of moisture below the roof membrane as it heats up would

decrease the membrane temperature (or slow the heating), and condensation of moisture

under the roof membrane would increase the roof membrane temperature (or slow cooling).

To assess the movement of moisture within the roof assemblies, the relative humidity

measured below the insulation is graphed for each of the roof membrane colours in Figure

3.37, Figure 3.38, and Figure 3.39. These figures are for June 30th, 2013 which is the same

time period as for the roof membrane cap sheet and metal deck temperature graphs

presented in Section 3.3.2 and Section 3.3.3.


Figure 3.37 Graph of relative humidity below the insulation for assemblies with a white cap sheet on June 30, 2013

Figure 3.38 Graph of relative humidity below the insulation for assemblies with a grey cap sheet on June 30, 2013

Figure 3.39 Graph of relative humidity below the insulation for assemblies with a black cap sheet on June 30, 2013

Each of the preceding three figures indicates the daily cycle of moisture movement within

the roof assemblies. As the temperature of the roof membrane increases during the day,

moisture is driven inwards and the relative humidity below the insulation increases. As the

0

10

20

30

40

50

60

70

80

90

100


Relative Humidity [%

] W‐ISO RH‐B‐INS

W‐ISO‐SW RH‐B‐INS

W‐SW RH‐B‐INS

0

10

20

30

40

50

60

70

80

90

100


Relative

Humidity [%

]

G‐ISO‐SW RH‐B‐INS

G‐SW RH‐B‐INS

G‐ISO RH‐B‐INS was damaged during installation; conseuqently, data is unavailable.

0

10

20

30

40

50

60

70

80

90

100


Relative

Humidity [%

]

B‐ISO RH‐B‐INS

B‐ISO‐SW RH‐B‐INS

B‐SW RH‐B‐INS


temperature of the roof membrane decreases at night, the moisture is then driven outward

and the relative humidity below the insulation decreases. This movement is noticeable in

all of the roof assemblies, and it is most significant for the stone wool assemblies and least

significant for the polyiso roof assemblies which is likely due to the stone wool being

significantly more vapour permeable than the polyiso. It is not readily apparent why the

white hybrid (W-ISO-SW) assembly demonstrates such large changes in relative humidity

compared to the grey and black ISO-SW roofs, but it is possible that a small quantity of

moisture entered the roof assembly during construction.

Cut tests were performed on September 26th, 2013 to assess the amount of moisture that

was present within the roof assemblies. These cut tests were performed in four different

locations including locations with different membrane colours and different insulation

arrangements. The cut tests were performed in the morning when frost was still present

on the membrane surface which is when the maximum amount of moisture would be

present on the underside of the roof membrane. Images of two of these cut tests are

provided in Figure 3.40 to Figure 3.41. All of these cut tests found no visible indications

of moisture within the roof assemblies.

Figure 3.40 Photo of cut test of stone wool insulation under white roof membrane cap sheet indicating no visible signs of moisture within the roof assembly

Figure 3.41 Photo of cut test of polyiso insulation under black roof membrane cap sheet indicating no visible signs of moisture within the roof assembly

Despite the extensive monitoring conducted for this study, it is not possible to quantify the

impact of the latent heat transfer that is occurring in the tested roof assemblies based on

the available information. Further research involving more detailed laboratory testing

would be required to quantify this effect. This research could also investigate the impact

of different amount of water being incorporated into the assembly to simulate rain events

and night sky condensation on exposed insulation which occur during construction and

then subsequently can be included within the assembly if not permitted to dry prior to

installation of the roofing membrane. Further research could also be performed to calibrate

the relative humidity levels measured within the assemblies with the associated moisture

content that would occur in the different materials (i.e. insulation types).

3.4 Dimensional Stability of Insulation

Previous investigation by RDH has indicated that shrinkage of polyiso roof insulation over

time can potentially negatively affect roof performance. While the roof membrane is

typically protected from damage due to shrinkage of the insulation boards by protection

boards installed over the insulation and under the roof membrane, gaps that can open up


between insulation boards can create thermal bypasses which potentially compromise the

thermal performance of the roofing assembly. These gaps could potentially be substantial

in size as the specification of polyiso insulation board which is provided by ASTM C1289

allows for 2% to 4% dimensional change (depending on the exposure conditions) which for

a 48” by 48” board could be as much as almost 2 inches. (NRCA, 1999)

3.4.1 Long-term Displacement

To investigate the relative dimensional stability and potential shrinkage of the polyiso and

stone wool insulation products used in this study, displacement sensors were installed in

the edges of the insulation boards along both the north-south and east-west axes in both

the lower layer of insulation and the upper layer for the white and black roofs. Figure 3.42

illustrates the arrangement of the insulation boards, adhesive, metal deck, open-web steel

joists, and displacement sensors.

Figure 3.42 Graph of relative humidity below the insulation for assemblies with a black cap sheet on June 30, 2013

It is important to note that the displacement sensors installed in the test roofs measure the

size of the gap between the boards, and that changes in this gap size could be the result

of insulation expansion or contraction, insulation shrinkage (permanent contraction) or

could alternatively be caused by movement of the insulation boards. Movement of the

insulation boards could potentially be driven by thermal expansion and contraction of the

roof membrane or by movement of the roof structure. Figure 3.43 illustrates how deflection

of the steel roof structure could manifest as changes in the gap size between insulation

boards.

Displacement sensor will be sandwiched against adjacent insulation board once installed.


Figure 3.43 Schematic cross-section of the roof assemblies showing how deflection of the structural steel trusses can cause changes in the gap size between the insulation boards

The effectiveness of the polyurethane foam adhesive used to adhere the insulation boards

could also have bearing on the measured changes in the size of the gap between the

insulation boards. Different insulation attachment strategies could provide substantially

different responses to movement of the insulation boards. While an adhered system would

likely provide a relatively stiff response until failure of the adhesive, and mechanically

fastened system would likely allow significantly more movement of the insulation boards.

To date, no significant difference in the gap between the insulation boards between the

north-south and east-west directions has been noticed. One example is provided in Figure

3.44 which compares the movement of the lower layer of the hybrid roof assemblies

(polyiso) in each direction and shows similar trends for each. Graphs for each roof type are

provided in Appendix A. Displacement is provided both in millimetres and in % change in

length of the board (change in length divided by length of insulation board, length of

insulation boards is 1219 mm (4 ft)), and negative displacement corresponds with an

increase in the gap between the boards, and potentially with shrinkage of the insulation

boards.

Deflection of steel deck

Deflection causing opening of joint between insulation boards

Potential compression of insulation due to deflection of steel deck


Figure 3.44 Graph of displacement of lower layer of insulation in hybrid roof assemblies (parenthesis indicate insulation type)

Given that there is no significant difference based on direction, north-south and east-west

displacements were averaged for the upper and lower layers of insulation in each roof

assembly. Figure 3.45 and Figure 3.46 provide graphs of these averages for comparing the

roofs with white and black cap sheets. These two figures indicate that there is no significant

correlation between the roof membrane colour and the insulation displacement.

Figure 3.45 Graph of insulation displacement averaged for both north-south and east-west direction for upper insulation layers

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun

Displacement [%

]

Displacement [m

m]

W‐ISO‐SW‐Lower‐W (ISO) B‐ISO‐SW‐Lower‐W (ISO)

W‐ISO‐SW‐Lower‐N (ISO) B‐ISO‐SW‐Lower‐N (ISO)

‐0.2

‐0.16

‐0.12

‐0.08

‐0.04

0

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacemen

t [%

]

Displacement [m

m]

W‐ISO‐Upper (ISO) W‐ISO‐SW‐Upper (SW) W‐SW‐Upper (SW)

B‐ISO‐Upper (ISO) B‐ISO‐SW‐Upper (SW) B‐SW‐Upper (SW)


Figure 3.46 Graph of insulation displacement averaged for both north-south and east-west direction for lower insulation layers

To evaluate the potential correlation between displacement and the insulation arrangement,

the displacement data was averaged for the lower and upper layers of each of the three

insulation arrangements and is plotted in Figure 3.47 and Figure 3.48 for the upper and

lower insulation layers respectively.

Figure 3.47 Graph of insulation displacement averaged for the upper insulation layer of each of the roof insulation arrangements

‐0.2

‐0.16

‐0.12

‐0.08

‐0.04

0

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐Lower (ISO) W‐ISO‐SW‐Lower (ISO) W‐SW‐Lower (SW)

B‐ISO‐Lower (ISO) B‐ISO‐SW‐Lower (ISO) B‐SW‐Lower (SW)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0


Displacemen

t [%

]

Displacemen

t [m

m]

ISO‐Upper (ISO) ISO‐SW‐Upper (ISO) SW‐Upper (SW)


Figure 3.48 Graph of insulation displacement averaged for the lower insulation layer of each of the roof insulation arrangements

These figures indicate that the lower layer of the hybrid roofs, which is polyiso, has

significantly more movement than the lower layers in either of the polyiso only or stone

wool only roof assemblies. This movement corresponds with the gap between the

insulation boards increasing, potentially due to shrinkage of the insulation boards. The

upper layers of insulation all show similar amounts of displacement over the course of the

monitoring period.

To facilitate the comparison of displacement of the lower layers versus displacement of the

upper layers, the data in Figure 3.47 and Figure 3.48 have been combined into Figure 3.49.

This graph illustrates that with the exception of the hybrid roof assembly, the upper

insulation layer typically has more displacement than the lower insulation layer.

Figure 3.49 Graph of insulation displacement averaged for the upper and lower insulation layer of each of the roof insulation arrangements

Overall, nearly all of the insulation has measured displacement of between 0.4 mm and 2.6

mm (0.03% to 0.20%) which corresponds with an increase in the size of the gap between

the insulation boards which could potentially be a result of shrinkage of the insulation

boards. No correlation was found between the amount of displacement and direction (i.e.

north-south or east-west) and roof membrane colour; however, the insulation arrangement

and the location of the insulation (lower or upper layer) did correlate with the measured

displacements. The gap in the polyiso layer in the hybrid roof assemblies was found to

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

ISO‐Lower (ISO) ISO‐SW‐Lower (ISO) SW‐Lower (SW)

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [m

m]

ISO‐Lower (ISO) ISO‐SW‐Lower (ISO) SW‐Lower (SW)

ISO‐Upper (ISO) ISO‐SW‐Upper (ISO) SW‐Upper (SW)


increase in size more than in the other lower layers of insulation, and in general the upper

layers were found to have displaced more than the lower layers.

Further research and continued monitoring of these insulation boards is necessary to

confirm these longer-term displacement trends. This could potentially include making

exploratory openings in the roof assemblies to confirm the size of the gaps between the

insulation boards. Work could also be carried out to investigate the potential driver of these

gaps between the insulation boards including deflection of the roof structure, thermal

expansion and contraction of the roof membrane, and potentially shrinkage of the

insulation boards.

3.4.2 Short-term Displacement

Changes in the size of the gap between the insulation boards is also noticeable over the

short-term. Figure 3.50 and Figure 3.51 show an example of this for June 30th, 2013 for

the upper and lower insulation layers in the black roofs. These figures show that in some

cases the upper layer of stone wool insulation shows significant movement which is

correlated with the temperature of the cap sheet; however this does not occur for all of the

stone wool roofs. The lower layer of insulation shows no displacement in relation to the

cap sheet temperature because it is separated from this change in temperature by the upper

layer of insulation. A similar trend was also determined for the white roofs and these graphs

are provided in Appendix A.

Figure 3.50 Graph of insulation displacement for the upper layer of insulation in the black roofs

0

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30

40

50

60

70

80

90

100

‐2

‐1.5

‐1

‐0.5

0

0.5

1


Cap

Sheet Temperature [°C]

Displacement [m

m]

B‐ISO Upper N

B‐ISO‐SW Upper N

B‐SW Upper N

B‐ISO Upper W

B‐ISO‐SW Upper W

B‐SW Upper W

B‐SW T‐CAP


Figure 3.51 Graph of insulation displacement for the lower layer of insulation in the black roofs

0

10

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30

40

50

60

70

80

90

100

‐2

‐1.5

‐1

‐0.5

0

0.5

1


Cap


Displacement [m

m]

B‐ISO Lower N

B‐ISO‐SW Lower N

B‐SW Lower N

B‐ISO Lower W

B‐ISO‐SW Lower W

B‐SW Lower W

B‐SW T‐CAP


4 Energy Modeling

Whole building energy modeling was performed to assess how the thermal performance of

the roof assemblies, as determined in the laboratory and field testing phases of the study,

affects whole building energy consumption in various North American climates.

Additionally, the energy modeling investigates the optimum roof membrane colour (solar

absorptivity) and insulation strategy for conventional roof assemblies in each of these

climates. Simulations were conducted to compare the same white, grey, and black roof

membranes, and the same polyiso, stone wool, and hybrid insulation arrangements as were

examined in the field monitoring component of this project.

The building energy modeling was conducted using the U.S. Department of Energy (DOE)

Building Energy Codes Program commercial building prototype model for a stand-alone

retail building designed to meet ASHRAE 90.1-2010 requirements. The building

information files are available online and use the hourly energy modeling program

EnergyPlus. (DOE, 2012)

One goal of the energy modeling was to investigate the impact of temperature dependant

insulation R-values on whole building energy consumption. This effect is typically not

modeled in most whole building simulation programs, but can be modeled in EnergyPlus

by making the conductivity of the insulation a function of temperature. Figure 4.1 shows

charts of the modeled energy consumption of the commercial retail building located in

Vancouver, BC first using constant conductivity values for the roof insulation based on the

rated thermal resistance, and then using temperature dependent insulation conductivities

based on the laboratory testing. Though the overall difference in heating consumption

between the two cases in this climate is low (typically within 1 kWh/m², 2%), these results

indicate that the polyiso has the lowest heating energy consumption when constant

conductivities are used, but stone wool insulation has the lowest heating energy

consumption when temperature dependent conductivities more consistent with field and

laboratory findings are used.

It is also important to note that the graphs in this section present totally building energy

consumption; however, the percent change in the heat flow through the roofs is much larger

than the percent change in the total building energy consumption. For example, in

Vancouver heat flow through the roof of the commercial retail building represents between

15% and 36% of the heat flow through the building enclosure depending on the insulation

and roof membrane scenario. Consequently, a 2% change in the overall energy

consumption of the building would correspond with approximately a 6% to 14% change in

the heat flow through the roof.


Figure 4.1 Chart of annual heating energy consumption for a commercial retail building located in Vancouver, BC using constant conductivites and temperature dependent conductivities for the roof insulation

The impact of insulation aging on building energy consumption was also assessed using

the commercial retail building energy model. The building was modeled using insulation

conductivities consistent with the initial thermal performance of the insulation, and then it

was modeled using conductivities consistent with the aged performance measured in the

laboratory. The results of this modeling are provided in Figure 4.2 and demonstrate a clear

increase in the energy consumption of the building using polyiso insulation between the

initially installed and aged cases. This effect is largest in the polyiso roof, making it the

case with the most annual heating energy use. The difference in heating energy between

the un-aged and aged cases would increase in more extreme climates than Vancouver.

Figure 4.2 Chart of annual heating energy consumption for a commercial retail building located in Vancouver, BC showing the differnce between the initial and aged insulation cases

To evaluate the impact of roof membrane colour and insulation arrangement on building

energy consumption throughout North America, energy models were developed for one

representative city in each of the eight ASHRAE climate zones. The climate zones and the

cities used for the modeling are illustrated in Figure 4.3.

35

36

37

38

39

40

41

42

43

44

45

Black Grey White Average

Annual Heating En

ergy

[kWh/m

²]


ISO

ISO‐SW

SW

35

36

37

38

39

40

41

42

43

44

45


Annual Heating En

ergy

[kWh/m

²]

ISO

ISO (Aged)

ISO‐SW

ISO‐SW (Aged)

SW

Constant Conductivity (Default)

Temperature Dependent Conductivity (Adjusted to match lab data)

5%2%


Figure 4.3 Map of ASHRAE Climate zones indicating the cities selected for the energy modeling

Figure 4.4, Figure 4.5, and Figure 4.6 show the annual heating, cooling, and total heating

and cooling energy consumption, respectively, for the commercial retail building in each of

the eight ASHRAE climate zones with black, grey, and white roof membranes, and aged

polyiso, stone wool, or hybrid insulation. The numerical results of this analysis are

tabulated in Appendix A.

Houston Miami

San Francisco Baltimore

Burlington Vancouver

Duluth

Fairbanks


Figure 4.4 Chart of annual heating energy use intensity for a commercial retail building in each of the eight ASHRAE climate zones

Figure 4.5 Chart of annual cooling energy use intensity for a commercial retail building in each of the eight ASHRAE climate zones

0

20

40

60

80

100

120

140

1Miami

2Houston

3San Francisco

4Baltimore

5Vancouver

6Burlington, V

T

7Duluth

8Fairbanks

Average

Annual Heating En

ergy [kWh/m

²]

B‐ISO (Aged) B‐ISO‐SW (Aged) B‐SW

G‐ISO (Aged) G‐ISO‐SW (Aged) G‐SW

W‐ISO (Aged) W‐ISO‐SW (Aged) W‐SW

0

20

40

60

80

100

120

140

1Miami

2Houston

3San Francisco

4Baltimore

5Vancouver

6Burlington, V

T

7Duluth

8Fairbanks

Average

Annual Coolin

g En

ergy [kWh/m

²]





Figure 4.6 Chart of annual heating & cooling energy use intensity for a commercial retail building in each of the eight ASHRAE climate zones

Comparing roof membrane colour, the buildings with black membranes use less heating

energy but more cooling energy, while the buildings with white roofs use more cooling

energy but less heating energy. The total heating and cooling plot (Figure 4.6) shows that

overall energy use is lower for white roofs in cooling dominated climate zones, and lower

for black roofs in heating dominated climate zones. This finding also suggests that in some

temperate climates there could theoretically be an optimal grey roof membrane colour for

energy efficiency. Across all climate zones, stone wool insulation results in the lowest

heating and cooling energy consumption, while aged polyiso insulation has the highest

energy consumption.

0

20

40

60

80

100

120

140

1Miami

2Houston

3San Francisco

4Baltimore

5Vancouver

6Burlington, V

T

7Duluth

8Fairbanks

Average

Annual Heating & Coolin

g En

ergy [kWh/m

²]





5 Discussion and Conclusions

A large-scale study incorporating a combination of laboratory testing, field monitoring, and

energy modelling was implemented to measure the impacts and benefits of roof membrane

color and insulation strategy on the long-term thermal and hygrothermal performance of

conventional roofing assemblies. At the study building in the Lower Mainland of British

Columbia, Canada, three different 2-ply SBS membrane cap sheet colors (white, grey, black)

were placed over three different conventional insulation strategies (polyiso, stone wool, and

a hybrid combination of both) creating a total of nine unique conventional roofing

assemblies. Sensors were installed within each of the roof assemblies to measure material

and surface temperatures, relative humidity, moisture content, heat flux, and dimensional

stability of the insulation.

As part of the study, thermal resistance testing of the polyiso and stone wool insulation

was performed using ASTM C518 procedures. The insulation products were tested at a

range of in-service temperatures, and a relationship between R-value and temperature was

developed. The results were then applied to the three insulation arrangements monitored

within this study to determine in-service apparent R-values based on exterior membrane

temperature. The findings show that the stone wool and hybrid roofs will maintain apparent

R-values close to rated values, whereas the apparent R-value in the polyiso roofs decreases

significantly when exposed to either extreme of cold or hot outdoor (and solar radiation

induced) temperatures. This is an important consideration when designing roof assemblies.

The difference in performance between the roofs with black, grey, and white membrane cap

sheets was examined using the field monitoring data. The in-service reflectance of these

roofs was measured and determined to be relatively similar to the rated reflectance and

also to not have significantly changed due to soiling of the roof membrane over the course

of the monitoring period except around drain locations. However, with continued exposure,

soiling of the roof membrane may worsen and affect the reflectance. Generally, the more

reflective the roof membrane, the lower the daily maximum membrane temperature and

the more moderate the fluctuations in interior metal deck temperature which will likely

extend the service life of the membranes, reduce heat gain in to the building through the

roof assembly, and improve the thermal comfort of the building occupants.

The relative performance of the three different roof insulation arrangements was also

evaluated using the field monitoring data. The heat flow (flux) and temperature

measurements show a difference in behaviour between the polyiso, stone wool, and hybrid

insulation strategies. The peak membrane temperature was reduced and offset for the

hybrid roof assemblies which is likely due to a combination of temperature dependent

thermal conductivity, thermal mass, and latent heat transfer effects; however, it was not

possible to fully determine the cause of this effect as part of this study. This reduction in

peak roof membrane temperatures positively affects the longevity of the membrane as it

reduces the rate of various weathering mechanisms. An offset was also noted in the

maximum metal deck temperatures, though the measured effect was different for the white

and grey roofs as compared to the black roofs. In all cases the hybrid and stone wool

insulation arrangements provided more stable interior metal deck temperatures and

consequently would likely provide improved thermal comfort for the building occupants.


Whole building energy modeling was performed to investigate the optimum roof membrane

color (solar absorptivity) and insulation strategy for a conventional roof with respect to

building energy consumption. Simulation runs were used to compare the same white, gray,

and black roof membranes, and polyiso, stone wool and hybrid insulation strategies as used

in the monitoring study, and accounted for the temperature dependence of the insulation

thermal resistance. Energy modeling of these variables was performed using the U.S.

Department of Energy (DOE) Building Energy Codes Program commercial building prototype

model for a stand-alone retail building designed to meet ASHRAE 90.1-2010 requirements.

Models were run for one representative city in each of the eight ASHRAE North American

climate zones.

Comparing roof membrane color across each climate zone, the black membrane uses less

heating energy but more cooling energy, while the white roof uses more heating energy but

less cooling energy. Overall energy use is lower for white roofs in cooling dominated climate

zones (zones 1 and 2), and lower for black roofs in heating dominated climate zones (zones

5 through 8). In mixed heating and cooling climate zones (zone 3 and 4), the differences

are very small between light and dark colored roof membranes. With membrane aging and

soiling, the cooling savings of white membranes will likely be reduced as the surface

reflectivity decreases; however, cleaning or recoating of the roof could potentially help to

maintain the roof reflectance.

Across all climate zones, the energy modeling indicates that the stone wool insulation

results in the lowest heating and cooling energy consumption for the same rated R-value,

while aged polyiso insulation has the highest energy consumption due to the loss of its

initial R-value. The hybrid approach of stone wool over polyiso results in a good compromise

of performance and maintains the higher R-value of the polyiso insulation by buffering it

from the exterior temperature.

Overall this study provides insight into the performance of conventional roof assemblies

depending on insulation arrangement and roof membrane solar reflectance (i.e. colour).

The findings of this study can be used to guide the design of conventional roof assemblies

to optimize both roof membrane durability and building energy performance.


6 Further Research

This study has identified a number of areas for potential further research that could be

pursued to continue to develop the understanding of conventional roof performance.

Potential further research areas include:

Continued monitoring and research to evaluate the long-term impact of roof

membrane soiling and potentially also of the effectiveness of cleaning and

recoating methods at restoring membrane reflectance.

Testing of samples of the aged roof membrane samples after additional years of

exposure to evaluate the effect of the roof membrane colour on the deterioration

of the membrane. This testing would likely include testing of the physical

properties of the aged membrane and comparison of the performance based on

the insulation arrangement on which it was placed and based on membrane colour.

Research to determine the optimal hybrid insulation split between polyiso and

stone wool insulation.

Laboratory testing to quantify the impact of latent heat transfer and thermal mass

on net heat transfer through the roof assemblies, roof membrane temperatures,

and interior metal deck temperatures. This research could include the intentional

introduction of water in to roof assemblies and could also work to calibrate the

relative humidity levels measured in the roof assemblies with the associated

moisture content of the different insulation products.

Continued monitoring and research to evaluate long-term displacement trends and

the impact on membrane durability and effective thermal performance. This

analysis could include the evaluation of potential drivers of these gaps including

roof membrane thermal expansion and contraction, roof deflection, and insulation

shrinkage.

Research to assess the performance of hybrid roof with different insulation types

including extruded polystyrene (XPS) and expanded polystyrene (EPS).

Research to assess the performance of different membrane types.

Similar field studies to evaluate the performance of conventional roof assemblies

in different climate zones.

Additional energy modeling to evaluate the impact of different roof colours and

insulation arrangements for building types including multi-unit residential,

commercial office towers, etc.

Monitoring of energy consumption of a building with different insulation

arrangements and/or insulation colours by monitoring it with one roof assembly

and then with an alternate roof assembly.


7 References

Akbari, H., Berhe, A., Levinson, R., Graveline, S., Foley, K., Delgado, A., & Paroli, R. 2005. Aging and Weathering of Cool Roofing Membranes. (LBNL-58055)

ASTM Standard C518, 2010, “Standard Test Method for Steady-State Thermal

Transmission Properties by Means of the Heat Flow Meter Apparatus” ASTM International, West Conshohocken, PA, 2010. Available at http://www.astm.org/Standards/C518.htm.

ASHRAE Standard 90.1 “Energy Standard for Buildings except Low-Rise Residential

Buildings” I-P and S-I Editions. 2007, 2010. ANSI/ASHRAE/IESNA. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Available at: http://www.ashrae.org.

Berdahl et al. (2008) Weathering of Roofing Materials - An Overview. Construction and

Building Materials, vol. 22, pg. 423-433. Building Science Corporation (BSC). 2013a. BSC Information Sheet 502: Understanding the

Temperature Dependence of R-values for Polyisocyanurate Roof Insulation. Available at: http://www.buildingscience.com.

Christian, J., Desjarlais, A., Graves, R., Smith, T. 1995. Five-Year Field Study Confirms the

PIMA Standard fro Estimating Polyisocyanurate Insulation Long-Term Thermal Performance. Proceedings of the 11th Conference on Roofing Technology, September 1995, Gaithersburg, MD.

DOE. 2012. Building Energy Codes Program – Commercial Prototype Building Models.

Available at: http://www.energycodes.gov/development/commercial/90.1_models DOE Cool Roof Calculator. 2013. Oak Ridge National Laboratory. Software Version 1.2.

Available online: http://web.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm. Dell, M. 1990. Behavioral characteristics of fully adhered modified bitumen roof

membranes when subjected to in-plane loads. University of Waterloo, 1990. Waterloo, Ontario.

Dell, M., and Finch, G., 2013. Monitored Field Performance of Conventional Roofing

Assemblies – Measuring the Benefits of Insulation Strategy. Proceedings from the 2013 RCI Symposium on Building Envelope Technology, November 13-14, 2013, Minneapolis, Minnesota.

Dell, M., Finch, G., Ricketts, L, and Hanam, B. 2014. Conventional Roofing Assemblies:

Measured Thermal Benefits of Light to Dark Roof Membranes and Alternate Insulation Strategies. Proceedings from the 2014 RCI Symposium on Building Envelope Technology, March 20-25, 2014, Anaheim, California.

Environment Canada. 2013. Canadian Climate Normals, Chilliwack Airport. Available at:

http://climate.weather.gc.ca/climate_normals/ Graham, M., 2010. Revised R-values, Professional Roofing, May 2010. Available at:

http://www.professionalroofing.net/. Graham, M., 2013. New LTTR values: PIMA updates its QualityMark Program. Professional

Roofing, vol. 42, issue 8, p 12, August 2013. Available at: http://www.professionalroofing.net/.

Graham, M., 2014. Polyiso’s R-value: NRCA recommends Polyisocyanurate insulation be

specified by its desired thickness. NRCA Industry Issue Update, January 2014. National Roofing Contractors Association, Rosemont, Illinois.


Hedlin, C.P., 1987. Seasonal Variations in the Modes of Heat Transfer in Moisture Porous Thermal Insulation in a Flat Roof. Journal of Thermal Insulation, Vol. 11, p 54-66, July 1987, (IRC Paper No. 1496).

Hedlin, C. 1988. Heat Flow Through a Roof Insulation Having Moisture Contents Between

0 and 1% by Volume, in Summer. ASHRAE Transactions 1988, Part 2, p 1579-1594. (IRC Paper No. 1636.)

Hewitt, V., Mackres, E., Shickman, K. 2014. Cool Policies for Cool Cities: Best Practices for

Mitigating urban Heat Islands in North American Cities. American Council for an Energy-Efficient Economy and Global Cool Cities Alliance, Washington, DC. (Report Number U1405)

Koshiishi, N., Shoji, T., Shimizu, I., Tanaka, K. 2014. Changes in the solar reflectance of

membrane waterproofing materials exposed to different atmospheric conditions. Proceedings from the International Conference on Building Envelope Systems and Technologies (ICBEST) 2014, June 9-12, 2014, Aachen, Germany.

NRCA, 2011. Special Report: Considerations Pertaining to Polyisocyanurate Insulation.

Accessed August 18, 2014 at http://www.nrca.net/roofing/-Special-Report-Considerations-Pertaining-to-Polyisocyanurate-Insulation-May-1999-263.

Roe, R. 2007. Long-Term Thermal Resistance (LTTR): 5 Years Later. Interface Technical

Journal, March 2007, p 12-15. Roof Savings Calculator (RSC). 2013. Oak Ridge National Laboratory and Lawrence

Berkeley National Laboratory. Software Version v0.92. Available online: http://www.roofcalc.com/index.shtml.

Siplast. 2010. Mass Effect – Substrate Influences on Modified Bitumen Roof Membrane

Longevity. North Vancouver, British Columbia, Canada. Smith, T.L., 2001. Benefits of Reflective Roofs in Northern Areas of the U.S.. Proceedings

of the 16th International Convention & Trade Show, April 20-24, 2001, Baltimore, Maryland.

Sproul, J., Pun Wan, M., Mandel, B. H., Rosenfeld, A. H. 2014. Economic comparison of

white, green, and black flat roofs in the United States. Energy and Buildings 71 (2014), p 20-27.

Zhao, L., Lee, X., Smith, R., Oleson, K. 2014. Strong contributions of local background

climate to urban heat islands – abstract. Accessed July 22, 2014 to http://www.nature.com/nature/journal/v511/n7508/full/nature13462.html


We trust that this report meets your needs at this time. Please contact the undersigned

with any questions or concerns.

Yours truly,

Lorne Ricketts | MASc, EIT Building Science Research Engineer (EIT) [email protected] RDH Building Engineering Ltd.

Graham Finch | MASc, P.Eng Principal, Building Science Research Specialist [email protected] RDH Building Engineering Ltd.

Marcus Dell | MASc, P.Eng. Managing Principal, Senior Building Science Specialist [email protected] RDH Building Engineering Ltd.

Ap

pen

dix

A

Ad

ditio

nal G

rap

hs


Additional graphs and data are provided in this appendix to supplement the main body of

the report. In some cases graphs are repeated here from the main body of the report for

completeness.

Maximum and Minimum Daily Membrane Temperatures

Figure A.1 Chart of monthly average peak daily membrane temperatures from May 2013 to April 2014

Figure A.2 Chart of monthly average reduction in peak daily membrane temperatures for the roofs with white membrane cap sheets as compared to the roofs with black membrane cap sheets

0

10

20

30

40

50

60

70

80


Temperature [°C]

W‐ISO

W‐ISO‐SW

W‐SW

G‐ISO

G‐ISO‐SW

G‐SW

B‐ISO

B‐ISO‐SW

B‐SW

* *

*W‐ISO‐SW had significant data loss in August and September which is likely the cause of colder than typical temperatures.


0

5

10

15

20

25


Decrease in

Temperature [°C]


* *

Figure A.3 Chart of monthly average reduction in peak daily membrane temperatures for the roofs with grey membrane cap sheets as compared to the roofs with black membrane cap sheets

Figure A.4 Chart of monthly average reduction in peak daily membrane temperatures for the roofs with white and grey membrane cap sheets as compared to the roofs with black membrane cap sheets for each of the insulation arrangements

0

5

10

15

20

25

30

35


Decrease in

Tem

perature [°C]

G‐ISO G‐ISO‐SW G‐SW

0

9

18

27

36

45

0

2

4

6

8

10

12

14

16

18


Decrease in

Temperature [°F]

Decrease in

Tem

perature [°C]

ISO ISO‐SW SW



Figure A.5 Chart of monthly average minimum daily membrane temperatures from May 2013 to April 2014

Heat Flux

Figure A.6 Graph of heat flux through the three polyiso roofs from June 2 to 8, 2013

Figure A.7 Graph of heat flux through the three hybrid roofs from June 2 to 8, 2013

‐5

0

5

10

15


Temperature [°C]

W‐ISO

W‐ISO‐SW

W‐SW

G‐ISO

G‐ISO‐SW

G‐SW

B‐ISO

B‐ISO‐SW

B‐SW

*W‐ISO‐SW had significant data loss in August and September which is likely the cause of colder than typical temperatures.

‐25

‐20

‐15

‐10

‐5

0

5

10


Heat Flux [W

/m²]

W‐ISO HF

G‐ISO HF

B‐ISO HF

Outw

ardHeat Flo

wInward

Heat Flo

w

‐25

‐20

‐15

‐10

‐5

0

5

10


Heat Flux [W

/m²]

W‐ISO‐SW HF

G‐ISO‐SW HF

B‐ISO‐SW HF

Outw

ardHeat Flo

wInward

Heat Flo

w

Figure A.8 Graph of heat flux through the three stone wool roofs from June 2 to 8, 2013

Figure A.9 Chart of monthly average daily heat flow through the roof assemblies for polyiso insulation arrangements

Figure A.10 Chart of monthly average daily heat flow through the roof assemblies for hybrid insulation arrangements

‐25

‐20

‐15

‐10

‐5

0

5

10


Heat Flux [W

/m²]

W‐SW HF

G‐SW HF

B‐SW HF

Outw

ardHeat Flo

wInward

Heat Flo

w

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Tran

sfer [W

∙hr/m² per day]

W‐ISO G‐ISO B‐ISO

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Tran

sfer [W

∙hr/m² per day]

W‐ISO‐SW G‐ISO‐SW B‐ISO‐SW


Figure A.11 Chart of monthly average daily heat flow through the roof assemblies for stone wool insulation arrangements

Figure A.12 Chart of monthly average daily heat flow through the roof assemblies for roofs with white cap sheet membrane

Figure A.13 Chart of monthly average daily heat flow through the roof assemblies for roofs with grey cap sheet membrane

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Transfer [W

∙hr/m² per day]

W‐SW G‐SW B‐SW

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Tran

sfer [W∙hr/m² per day]


‐200

‐150

‐100

‐50

0

50

100


Daily Energy Transfer [W∙hr/m² per day]

G‐ISO G‐ISO‐SW G‐SW

Figure A.14 Chart of monthly average daily heat flow through the roof assemblies for roofs with black cap sheet membrane

Figure A.15 Chart of monthly average daily heat flow through the roof assemblies averaged for each roof membrane cap sheet colour and showing percent of the data points that are missing in each month due to failure of the data collection equipement

Figure A.16 Chart of monthly average daily heat flow through the roof assemblies averaged for each insulation arrangement and showing percent of the data points that are missing in each month due to failure of the data collection equipement

‐200

‐150

‐100

‐50

0

50

100


Daily Energy Transfer [W

∙hr/m² per day]

B‐ISO B‐ISO‐SW B‐SW

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

‐200

‐150

‐100

‐50

0

50

100

150

Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun

Daily Energy Tran

sfer [W

∙hr/m² per day]

White Grey Black % Data Missing

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

‐150

‐100

‐50

0

50

100

Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May JunDaily Energy Transfer [W∙hr/m² per day]

ISO ISO‐SW SW % Data Missing


Dimensional Stability

Figure A.17 Graph of displacement of lower layer of insulatoin in polyiso roof assemblies (parenthesis indicate insulation type)

Figure A.18 Graph of displacement of lower layer of insulatoin in hybrid roof assemblies (parenthesis indicate insulation type)

Figure A.19 Graph of displacement of lower layer of insulatoin in stone wool roof assemblies (parenthesis indicate insulation type)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐Lower‐W (ISO) B‐ISO‐Lower‐W (ISO) W‐ISO‐Lower‐N (ISO) B‐ISO‐Lower‐N (ISO)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐SW‐Lower‐W (ISO) B‐ISO‐SW‐Lower‐W (ISO)

W‐ISO‐SW‐Lower‐N (ISO) B‐ISO‐SW‐Lower‐N (ISO)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐SW‐Lower‐W (SW) B‐SW‐Lower‐W (SW) W‐SW‐Lower‐N (SW) B‐SW‐Lower‐N (SW)

Figure A.20 Graph of displacement of upper layer of insulatoin in polyiso roof assemblies (parenthesis indicate insulation type)

Figure A.21 Graph of displacement of upper layer of insulatoin in hybrid roof assemblies (parenthesis indicate insulation type)

Figure A.22 Graph of displacement of upper layer of insulatoin in stone wool roof assemblies (parenthesis indicate insulation type)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐Upper‐W (ISO) B‐ISO‐Upper‐W (ISO) W‐ISO‐Upper‐N (ISO) B‐ISO‐Upper‐N (ISO)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐SW‐Upper‐W (SW) B‐ISO‐SW‐Upper‐W (SW)

W‐ISO‐SW‐Upper‐N (SW) B‐ISO‐SW‐Upper‐N (SW)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐SW‐Upper‐W (SW) B‐SW‐Upper‐W (SW) W‐SW‐Upper‐N (SW) B‐SW‐Upper‐N (SW)


Figure A.23 Graph of displacement of insulation for roof with white membrane cap sheet (parenthesis indicate insulation type)

Figure A.24 Graph of displacement of insulation for roof with black membrane cap sheet (parenthesis indicate insulation type)

Figure A.25 Graph of insulation displacement for the upper layer of insulation in the white roofs

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

W‐ISO‐Lower (ISO) W‐ISO‐SW‐Lower (ISO) W‐SW‐Lower (SW)

W‐ISO‐Upper (ISO) W‐ISO‐SW‐Upper (SW) W‐SW‐Upper (SW)

‐0.20

‐0.16

‐0.12

‐0.08

‐0.04

0.00

0.04

‐2.5

‐2.0

‐1.5

‐1.0

‐0.5

0.0

0.5


Displacement [%

]

Displacement [m

m]

B‐ISO‐Lower (ISO) B‐ISO‐SW‐Lower (ISO) B‐SW‐Lower (SW)

B‐ISO‐Upper (ISO) B‐ISO‐SW‐Upper (SW) B‐SW‐Upper (SW)

0

10

20

30

40

50

60

70

80

90

100

‐2

‐1.5

‐1

‐0.5

0

0.5

1

Jun 30 Jun 30 Jun 30 Jun 30 Jul 1

Cap


Displacement [m

m] W‐ISO Upper N

W‐ISO‐SW Upper N

W‐SW Upper N

W‐ISO Upper W

W‐ISO‐SW Upper W

W‐SW Upper W

W‐ISO T‐CAP

Figure A.26 Graph of insulation displacement for the lower layer of insulation in the white roofs (data unavailable for ISO roofs)

Whole Building Energy Consumption Modeling Data

ANNUAL HEATING ENERGY [kWh/m² (% savings compared to maximum]

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B-ISO (aged) 0

(22%) 4

(9%) 6

(20%) 18

(13%) 40

(10%) 38

(9%) 54

(8%) 114 (3%)

34 (7%)

B-ISO-SW (aged) 0 (21%)

4 (11%)

6 (20%)

16 (20%)

39 (13%)

35 (18%)

49 (18%)

102 (13%)

31 (15%)

B-SW 0 (23%)

3 (13%)

6 (20%)

15 (26%)

39 (14%)

33 (23%)

46 (22%)

99 (16%)

30 (19%)

G-ISO (aged) 0

(20%) 4

(8%) 7

(16%) 18

(11%) 41

(9%) 39

(8%) 55

(7%) 115 (3%)

35 (6%)

G-ISO-SW (aged) 0 (19%)

4 (10%)

7 (18%)

17 (18%)

40 (11%)

35 (17%)

49 (17%)

103 (13%)

32 (14%)

G-SW 0

(21%) 3

(12%) 7

(19%) 15

(25%) 39

(13%) 33

(21%) 47

(21%) 99

(16%) 30

(18%)

W-ISO (aged) 0 (max)

4 (max)

8 (max)

20 (max)

45 (max)

42 (max)

59 (max)

118 (max)

37 (max)

W-ISO-SW (aged) 0 (2%)

4 (4%)

8 (4%)

19 (9%)

43 (4%)

38 (10%)

52 (12%)

106 (11%)

34 (9%)

W-SW 0

(6%) 4

(7%) 8

(6%) 17

(17%) 42

(7%) 36

(16%) 50

(16%) 102

(14%) 32

(13%)

0

10

20

30

40

50

60

70

80

90

100

‐2

‐1.5

‐1

‐0.5

0

0.5

1

Jun 30 Jun 30 Jun 30 Jun 30 Jul 1

Cap


Displacement [m

m]

Insualation Displacement ‐White Lower

W‐ISO Lower N

W‐ISO‐SW Lower N

W‐SW Lower N

W‐ISO‐SW Lower W

W‐ISO‐SW Lower W

W‐SW Lower W

W‐ISO T‐CAP


ANNUAL COOLING ENERGY [kWh/m² (% savings compared to maximum]

1

Mia

mi

2

Houst

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3

San F

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B-ISO (aged) 61 (max)

36 (max)

4 (max)

20 (max)

2 (max)

9 (max)

6 (max)

3 (max)

18 (max)


35 (4%)

4 (6%)

19 (4%)

2 (7%)

9 (5%)

6 (4%)

3 (1%)

17 (4%)

B-SW 58 (5%)

34 (5%)

3 (8%)

18 (6%)

2 (9%)

9 (6%)

5 (6%)

3 (1%)

17 (5%)

G-ISO (aged) 60 (2%)

36 (2%)

4 (4%)

19 (2%)

2 (5%)

9 (3%)

6 (4%)

3 (3%)

17 (3%)


34 (6%)

3 (9%)

18 (7%)

2 (10%)

9 (7%)

5 (7%)

3 (3%)

17 (6%)

G-SW 57 (6%)

34 (7%)

3 (11%)

18 (8%)

2 (13%)

9 (9%)

5 (8%)

3 (3%)

16 (7%)

W-ISO (aged) 53 (13%)

32 (13%)

3 (26%)

16 (17%)

1 (28%)

7 (20%)

5 (21%)

3 (16%)

15 (15%)


32 (13%)

3 (25%)

16 (17%)

1 (27%)

8 (19%)

5 (20%)

3 (15%)

15 (15%)

W-SW 53 (14%)

32 (13%)

3 (25%)

16 (17%)

1 (28%)

8 (19%)

5 (20%)

3 (14%)

15 (15%)

ANNUAL HEATING & COOLING ENERGY [kWh/m² (% savings compared to maximum]

1

Mia

mi

2

Houst

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3

San F

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4

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5

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B-ISO (aged) 62 (max)

40 (max)

10 (6%)

37 (max)

42 (9%)

48 (4%)

60 (6%)

117 (3%)

52 (0%)


38 (4%)

10 (8%)

35 (6%)

41 (11%)

44 (12%)

54 (15%)

106 (13%)

48 (7%)

B-SW 58 (5%)

38 (5%)

10 (9%)

34 (10%)

40 (13%)

41 (17%)

52 (19%)

102 (16%)

47 (10%)

G-ISO (aged) 60 (2%)

39 (2%)

10 (4%)

37 (0%)

43 (7%)

48 (4%)

61 (5%)

118 (2%)

52 (0%)


38 (6%)

10 (8%)

35 (6%)

42 (10%)

44 (12%)

54 (14%)

106 (12%)

48 (7%)

G-SW 58 (6%)

37 (7%)

10 (9%)

33 (11%)

41 (12%)

42 (16%)

52 (18%)

102 (15%)

47 (10%)

W-ISO (aged) 53 (13%)

36 (11%)

11 (max)

37 (2%)

46 (max)

50 (max)

64 (max)

121 (max)

52 (max)


35 (11%)

11 (3%)

35 (7%)

44 (4%)

45 (9%)

57 (11%)

108 (10%)

49 (7%)

W-SW 53 (14%)

35 (12%)

10 (4%)

33 (11%)

43 (6%)

43 (13%)

55 (14%)

104 (14%)

47 (10%)

study of conventional roof performance · 3.4.1 long-term displacement 42 ... while insulation...

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