the influence of insulation styles on the air conditioning ... · yupeng wang is a postdoc fellow...

Yupeng Wang is a Postdoc Fellow in the Department of BCEE, Concordia University, Montreal, Canada. Hiroatsu Fukuda is a Professor at the University of Kitakyushu, Kitakyushu, Japan.

The Influence of Insulation Styles on the

Air Conditioning Load of Japanese Multi-

Family Residences

Yupeng Wang1, and Hiroatsu Fukuda

2

1Department of BCEE, Concordia University, Canada, Email: [email protected] 2Department of Architecture, The University of Kitakyushu, Japan

ABSTR ACT HEADING

The performance of building envelopes significantly affects the indoor energy consumption,

thermal comfort, and durability of a building. Numerous studies have focused on the thickness of

insulation materials and considerations for insulation placement (installing insulation inside or outside

the wall), however most of the studies have discussed insulation placement in each building’s

components and form (wall, roof, floor), and very few of them have considered the insulation as an

insulation system of the building. In 1999, the Japanese Institute for Building Environment and Energy

Conservation issued the standards for residential energy efficiency that specified the standards of

building envelope thermal transmittance and overall heat loss coefficients however; the insulation

placement was not well explained. Additionally, it is common in Japan to use intermittent air-condition

systems rather than having the air conditioning units continuously operating. It is necessary to

investigate the performance of insulation taking into consideration the specific life styles of people living

and working in Japan. In this research, we will (1) develop new interior insulation to conduct insulation

on all of the interior surfaces of building units (walls, ceilings and floors) for environmental building

design based on the calculation of heat loss; (2) discuss and demonstrate the effect of high heat capacity

on each of the building components and thermal bridge by building environmental simulations; (3) carry

out the simulation in different cities in Japan (Sapporo, Hachinohe, Sendai, Toyama, Tokyo, Miyazaki

and Naha) and discuss the applicability in these different areas of Japan. Comparing the environmental

qualities among three insulation styles (outside insulation on outside walls, inside insulation on outside

walls, and interior insulation which is an innovative insulation style in Japan), the energy saving and

thermal comfort advantages will be demonstrated. This research will provide an innovative insulation

style that could contribute to new generations of energy-saving standards and formulations in Japan.

INTRODUCTION

In order to tackle global environmental issues in Japan, the “Act of The Rational Use of Energy”

and the “Energy-Saving Standards for Houses and Buildings” were reformed in May 2008 and January

2009 respectively (IBEEC, 2009). These were aimed not to improve energy conservation performance at

individual houses, but rather to focus on promoting and spreading energy savings throughout the whole

housing industry, indicating that further discussion of housing energy savings will be anticipated.

Therefore, we once again need to clarify the features of different insulations in common housing

complexes, as well as how insulation affects indoor thermal environment and energetic load (Wang et

al., 2010). Meanwhile, the building envelope thermal performance consideration shows building

materials with high thermal insulation properties should be used in the outer walls, floors and other parts

30th INTERNATIONAL PLEA CONFERENCE16-18 December 2014, CEPT University, Ahmedabad

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of the building envelop (Evans et al., 2009). This guideline is not including a detailed indication about

the difference of outside and inside insulation with a dynamic indoor and outdoor enviormant and the

comparsion of the impacts of Heat Bridges. We need to coordinate indoor thermal environment that are

looked around about thermal comfort as shown by (Kuma et al., 2008). This study aimed indoor thermal

environment and comfort. Three insulation methods were compared from an indoor thermal environment

perspective in which the room temperature, surface temperature, operative temperature at a model

dwelling unit was adjusted by Thermal Load Calculation Software (THERB) to modify conditions such

as location, climate and air conditioning. This research could contribute to the expansion of Japanese

sustainable building standard development.

METHODOLOGY

Environmental Simulation Program

For the environmental performance evaluation, simulation program “THERB” was used in this

research. THERB for this analysis is dynamic simulation software which can estimate temperature,

humidity, sensible temperature, and heating/cooling loads for multiple-zone buildings (Ozaki, 2004;

Ozaki and Tsujimaru, 2006). THERB has the following features:

1) Successive transition method and a trapezoid hold function that can adjust itself to a time-

discrete domain are used.

2) Dimensionless equations are used to calculate convective heat transfer coefficients for every part

of the unit under study.

3) Longwave and shortwave absorption coefficients are taken into account in order to simulate the

net absorption of radiant heat and transmitted solar radiation.

4) A multilayer window model, which defines the overall transmittance, absorptance, and

reflectance of solar radiation, is used. (At present, the model cannot account for window curtains.)

5) A network airflow model is used to calculate ventilation quantities.

Model

The unit model that used in this simulation is a common dwelling in a residential complex in

Tokyo; that mentioned in Journal of Architectural Knowledge (2004). We are going to analysis the unit

which is on the middle floor, at the centre of the floor. Figure 1 shows floor plan, and figure 2 shows the

details of three insulation types.

Figure 1. Unit Plan Figure 2. Details of the Three Heat-Insulation Styles, Dark Circles are

Showing the Locations of Heat Bridge

[Type a quot

South

South

Sout

h

Outside Insulation Inside Insulation Interior Insulation

Balcony Living Room Living Room Living Room

Living Room Living Room Living Room

Balcony Balcony Balcony

Pla

ns

Sect

ion

s

30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad

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Heat Insulation Styles

In the 1980s, interior insulation used to be the common insulation style in Japan. However, dewing

inside of the wall was observed in most of inside insulation buildings, because of the underdeveloped

construction technique at that age. After that, outside insulation is becoming the common insulation style

in Japan, but the performance on thermal comfort and energy consumption between these two insulation

styles are still being argued in the academic world. A new insulation style as the promoted inside

insulation is proposed and compared with the traditional outside insulation and inside insulation.

In the interior insulation method, not only areas exposed to the air such as external wall and roof

but also confining wall, flooring and ceiling were insulated aiming to insulate the whole building from

the inner side. We complied with the Next Generation Energy-Saving Standards regarding what

materials were used, how thick they were or where they were installed. Three kinds of Class A Extruded

Polystyrene Form Heat Insulation were mainly used as insulation materials. High Grade Glass Wool

16K was used on the flooring only for the interior insulation4). Except for the external wall and roof for

the interior insulation, the thicknesses of insulation materials were 30mm Class A Extruded Polystyrene

Form Heat Insulation for walls and 50mm High Grade Glass Wool 16K insulation for flooring. Figure 2

and Table 2 show location and thickness of insulation materials.

HEAT LOSS CALCULATION

Currently, in Japan, standards and guidelines such like CASBEE and “Explanation of the energy-

saving standards for houses” are indicated the performance about inside insulation and outside insulation

of exterior walls and floors. However, these discussions are not including the consideration about

interior walls and ceiling, which also has a high heat capacity to affect the indoor thermal comfort and

energy use. Meanwhile, heat loss through Heat Bridge is also a big issue of building thermal

performance. In this section, thermal resistance and thermal transmittance are calculated following

equation 1 and 2, and the results are showing in table 1. The total heat loss by thermal transmittance of

the unit model is calculated according to equation 3 and the unit construction and volum, and the result

is shown in figure 3.

Thermal Resistance (m2·K/W) = Thickness (m) / Thermal Conductivity (W/m·K) (1)

Thermal Transmittance (U) (W/m2·K) = 1 / Thermal Resistance (m2·K/W) (2)

Heat Loss through Thermal Transmittance (W/K) = U·A·K (3)

Where: U is Thermal Transmittance (W/m2·K)

A is Area (m2)

K is Temperature Difference Coefficient (K=1.0, for exterior walls)

Table 1. Thermal Transmittance Calculation

Exterior Walls Heat Bridge

Thermal Thermal conductivity resistance

(m) (W/m·K) (m2·K/W)Extruded poly styrene foam blooks A-3

Concrete 0.20 1.600 0.13

Plaster board 0.01 0.220 0.05

1.24

0.81

0.03 0.028 1.07

Total thermal resistance (m2·K/W)

Thermal transmittance (W/m2·K)

Thickness Thermal Thermal conductivity resistance

(m) (W/m·K) (m2·K/W)

Concrete 0.20 1.600 0.13

Plaster board 0.01 0.220 0.05

0.17

5.87

Total thermal resistance (m2·K/W)

Thermal transmittance (W/m2·K)

Thickness


3

Figure 3. Heat Loss by Thermal Transmittance with Three Insulation Styles

As the result in the table 1, the thermal transmittance of Heat Bridge is over 7 times of that of

exterior walls. Heat loss through Heat Bridge is obveriously higher than that through exterior walls.

According to that pointed in figure 2, Heat Bridge in the units with exsting outside insulation and inside

insulation style could be founded between the floor and the exterior walls, and between the pillers and

interior walls. In the porposed interior insulation unit, Heat Bridge could be avoided by conducting

insultion at all of the interior surfaces. Compare the total heat loss through unit envelop among three

insulation types, the unit with inside insulation is slightly higher than outside insulation unit. This is

because of the Heat Brigh between the pillers and the interior walls which is not exst in outside

insulation units. The heat loss in units with interior insulation is about 40% lower than the other two

units. This is because of the promotion in the respect of Heat Bridge. Heat loss through the exterior walls

is also slightly changed by the different insulation thickness requirement by “Explanation of the energy-

saving standards for houses” in Japan, which is indicated in table 2. But the consideration of the whole

unit and the comprehensive building envelop thermal performance, the consideration of the complete

combination of the insulation performance in each building components is also an important issue for

building thermal insulation.

AC ENERGY CONSUMPTION IN VARIED JAPANESE CITIES

Simulation Details

In this simulation, we used reference data from Expanded AMeDAS Weather Data that in the

period between 1981 and 2000. We compared the effects with different weather conditions. We chose

seven target cities in six areas that assigned in Japanese Next Generation Energy-Saving Standards

(Explanation of the energy-saving standards for houses) by different weather characters. Figure 4 shows

the location of seven cities. The average temperature in north cities is lower than that in south cities.

According to different areas, the recommended thicknesses of insulation materials are provided in

the Explanation of the energy-saving standards for houses in Japan. The detail of varied insulation

materials thickness is showing in table 2. Considering the different characters of seven cities, heating

and cooling periods are varied. Heating period is that monthly average temperature is equal to or lower

than 15 ℃ (setting temperature: 20 ℃, percentage humidity: 40%). Period of cooling is that which

monthly average temperature is higher than 15 ℃ (setting temperature: 26 ℃, percentage humidity:

60%). Table 3 shows varied heating and cooling period in different cities.

To observe how difference in life style affects heat load, we prepared four different air-conditioned

rooms where residents with a different lifestyle were allocated to live with different AC usage patterns.

Table 4 shows the AC details. These conditions were as follows:

①. No one is at home during the day, and the air-conditioner is not in use during sleeping hours. (A

couple with dual income no kids – DINK);


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②. No one is at home during the day, and the air-conditioner is not in use during sleeping hours. (A

family consisting of a husband, a full-time housewife and a primary school child.);

③. No one is at home during the day, and the air-conditioner is in use during sleeping hours. (An

elderly couple);

④. 24-hour air-conditioning.

Additionally, all rooms were continuously ventilated once every two hours, as well as

automatically ventilated on an as-needed basis in the living room, dining room, kitchen and bathroom.

Area Thickness (mm) Outside Inside Interior

Ceiling 85 105 105

Exterior Wall 55 65 65

Ceiling 65 80 80


Ceiling 60 70 70


Ceiling 60 70 70


1

2

3, 4, 5

6

Figure 4. Weather Areas and Target Cities

Table 3. Heating and Cooling Periods in Different Cities (Kuma et al., 2008)

1 Sapporo, 2 Hachinohe 3 Sendai, 4 Toyama 4 Tokyo 5 Miyazaki 6 Naha

Heating Period Jan.-May, Oct.-Dec. Jan.-Apr., Nov.-Dec. Jan.-Mar., Nov.-Dec. Jan.-Mar., Dec.

Cooling Period Jun.-Sep. May-Oct. Apr.-Oct. Apr.-Nov. Jan.-Dec.

Table 4. AC Operating Details

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Living Room 6 Hours

Master Room 2 Hours

Child's Room 0 Hours

The Others 0 Hours

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Living Room 11 Hours

Master Room 2 Hours


The Others 0 Hours

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24


Master Room 11 Hours


The Others 0 Hours

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24


Master Room 24 Hours


The Others 24 Hours

AC off

AC

③

AC

①

AC

②

AC

④

AC on

Table 2. Thickness of Insulation Materials


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Effect Variation in Japanese Cities (Simulation Result 1)

Figure 5. Heating Load in Seven Japanese Cites with all AC Usage Patterns

Figure 6. Cooling Load in Seven Japanese Cites with all AC-usage Patterns

Figure 7. Annual AC Load in Seven Japanese Cites with all AC Usage Patterns

Figure 5 shows the comparison of heating load in seven Japanese cites with all AC usage patterns.

Overall, heating load in warm city is lower than that in cold city. In the seven cities with four AC usage

patterns, heating load of interior insulation unit is lower than that of outside insulation unit. The average


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decreased ratio is 29.7%. The highest decreased ratio is 45.5% in Miyazaki with using AC ④. Heating

load of inside insulation unit is slightly lower than that of outside insulation. The averagely decreased

ratio is 0.9%.

Figure 6 shows cooling load in summer in the units with varied conditions. Cooling load in north

cities is lower than that in south cities. Cooling load in Sapporo is the lowest, and that in Naha is the

highest. Cooling load of inside insulation unit is mostly higher than that of outside insulation unit, except

using AC ① in Naha. Cooling load in inside insulation unit is averagely 3.7% higher than that in outside

insulation unit. In interior insulation unit, cooling load is mostly higher than that in outside insulation

unit. The highest ratio of the difference is using AC ① in Sapporo, cooling load of interior insulation

unit is 56.3% higher than that of outside insulation unit. However, with using AC ④ in Tokyo, Miyazaki

and using AC ③,④ in Naha, cooling load is lower in interior insulation unit than that in outside

insulation unit. Generally, the differences between three insulation types are not as big as heating load in

winter.

Figure 7 shows AC load in seven Japanese cities. In warmer cities, annual AC load is lower than

that in colder cities. This is because heating load consists mostly of annual AC load. Annually, with the

same AC usage pattern in a same city, AC load of apartment unit with outside insulation is higher than

that of inside insulation unit. AC load of interior insulation unit is the lowest in the units with three

varied insulation styles. AC load of inside and outside insulation units is very small. In all of the cases,

inside insulation unit is averagely 0.5% lower than that of outside insulation unit. For comparison, AC

load of interior insulation unit is averagely 25.8% lower than that of outside insulation unit. The highest

ratio of AC load decrease between these two insulation styles is 39.7%, in Hachinohe, using AC ④. In

Sapporo, almost 100% of AC consumption is heating. And the heating load in Hachinohe and Sendai is

over 90% of annual AC load. On another hand, in Naha, annual ratio of heating load is under 15%. How

to reduce heating load in northern cities is an important mission.

Effects of Heat Capacity on Indoor Thermal Environment (Simulation Result 2)

Outside Insulation Interior Insulation

Figure 8. Cooling Load and temperature change in two summer days with outside insulation and interior

insulation from 15th

to 16th

, August, use AC ④, in Tokyo

For demonstrating the effect from the high heat capacity walls, the comparsion of indoor air

temperature and wall surface temperatures are carried out in the figure 8. The peak of outdoor air

temperature is observed between 12am to 15pm. In outside insulation, the peak temperature of exterior

and interior walls surface is observed around 18pm, about 3 to 6 hours later than the outside air

temperature. This is because of the high heat capacity of interior building materials. In the interior

insulation unit, the peaks of interior surfaces are the same of outside air temperature, and the temperature

of interior wall surface temperature is about 1.5 ℃ lower than that in outside insulation unit. Therefore,

low heat capacity of walls creats a controllable indoor thermal condition, and reduces cooling load in

summer days.


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CONCLUSION

In this paper, an innovative insulation style of interior insulation is proposed and investigated. A

calculation of heat loss in three types of insulated units demonstrated the mechanism of heat loss through

Heat Bridge, and the advantage of interior insulation. Heat Bridge in outside and inside insulation units

is distinctly effect to the building thermal performance, and the heat loss through Heat Bridge is avoided

by interior insulation implement. Subsequently, AC load and thermal comfort of apartment unit with

three insulation types are compared and discussed with numerical simulation. In both of heating and

cooling seasons, indoor air temperature of outside insulation unit is the most stable. In cooling season,

indoor temperature of the interior insulation unit is the lowest in three insulation type units when the

cooling is not in use. Look at the AC load, it is various in different cities and seasons. Compare to

outside and inside insulation units, annual AC load of interior insulation unit is the lowest in all of the

conditions.

In terms of indoor thermal environment, outside insulation is the best to stabilize room temperature.

However, in winter, the temperature of indoor wall surfaces in outside insulation unit is much lower than

that in interior insulated unit. This leads to an uncomfortable indoor environment and high heating

energy comsumption.

Finally, as we discussed about the features of the three insulation styles, the advantage of new

proposed interior insulation is demonstrated, and the advantages and disadvantages of these three

insulation styles are verified and expounded. Various factors should be considered such as regional

characteristics, insulation efficiency levels and design conditions, before the building will be built.

REFERENCES

Architectural Institute of Japan (2005): Expanded AMeDAS Weather Data (1981-2000).

Evans M, Shui B, Takagi T. Country report on building energy codes in Japan[J]. Geriatrics, 2009: 2.

Kuma Y., Ozaki A., OZASA (KAGAWA) H., Fukuda H. (2008) Influence of Moisture Sorption and

Desorption of Walls on Space Conditioning Load, Journal of Environmental Engineering, AIJ. Vol.

73 No. 632, pp. 1171-1178.

Ozaki A. (2004). Simulation Software of the Hygrothermal Environment of Buildings Based on Detailed

Thermodynamic Models, eSim 2004, The Canadian Conference on Building Energy Simulation,

pp.45-54.

Ozaki A., Tsujimaru T. (2006): Prediction of Hygrothermal Environment of Buildings Based upon

Combined Simulation of Heat and Moisture Transfer and Airflow, The Journal of the International

Building Performance Simulation Association, Vol.16, No.2, pp.30-37.

The Institute for Building Environment and Energy Conservation (IBEEC) (2009): Explanation of the

energy-saving standards for houses. Japan

Wang Y, Fukuda H, Kuma Y, et al. (2010): Study of Air-Conditioning Load: Comparison of Steel and

RC Residence Units[J]. Journal of Asian Architecture and Building Engineering, 9(2): 571-576.


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the influence of insulation styles on the air conditioning ... · yupeng wang is a postdoc fellow...

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