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Enclosure Design

Training

AIA Portland

August 2016

Martin Houston

AIA, CSI, LEED AP

Walsh Construction Co.

CLEAResult

Energy Trust of Oregon

Enclosure Design Training

• The role of the Building Enclosure in the creation

of Low Energy Buildings

• Critical Barriers (Control Layers)

• The Thermal Control Layer

• The Air Control Layer

2

Presentation Outline

• Definitions

• Control Layers

• The Thermal Control Layer

• The Air Control Layer

3

Definition:

Water Vapor

Water in it’s gaseous state

4

Definition:

Water Vapor

Water in it’s gaseous state

5

Definition:

Water Vapor Diffusion

The process by which water vapor spreads or

moves through permeable materials caused

by a difference in water vapor pressure.

6

7

Definition:

Vapor Permeability

Permeability, rated in Perms, is a measure of

the rate of transfer of water vapor through a

material.

The higher the number, the easier it is to pass

water vapor through a material.

8

Vapor Permeability of

Standard Building Materials

1. Polyethylene .06

2. XPS Rigid 1

3. OSB 2

4. Plywood 3.5

5. EPS Rigid 3.5

6. 15# Felt 6

7. 2 PSJTX 11

8. Tyvek CW 23

9. Cat5 18

10. Vaproshield 50/212

9

Definition:

Condensation

Condensation is the change in the phase of

water from the gaseous phase into liquid

droplets or solid grains .

10

11

Definition:

Dew Point

• The dew point is the temperature to which a

given parcel of air must be cooled, at

constant barometric pressure, for water vapor

to condense into water.

12

13

14

Pop Quiz

1. How many of you know the difference

between an air barrier, a weather resistive

barrier and a vapor barrier?

2. How many materials do you need to have all

three in one wall

15

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17

The Path to Low Energy Buildings

1

2

3

4

18

Basic Building

Design

Enclosure

MEP

On-site Renewable

Energy

The Path to Low Energy Buildings

1

2

3

4

19

Basic Building

Design

Enclosure

MEP

On-site Renewable

Energy

Load Reduction

The Path to Low Energy Buildings

1

2

3

4

20

Basic Building

Design

Enclosure

MEP

On-site Renewable

Energy

Load Reduction

Meeting loads as

efficiently and cleanly

as possible…

The Path to Low Energy Buildings

1

2

3

4

21

Basic Building

Design

Enclosure

MEP

On-site Renewable

Energy

Load Reduction

Enclosure – Key Attributes

• Insulation

• Airtightness

• Optimized

Glazing

22

Basic Building Design (BBD)

• Low energy building design should focus first

on a few basic building design concepts:

– Building size & shape • As small as possible for the given program

• As compact as possible for the given program, relative to climatic

factors

– Building orientation

– Optimized glazing design

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E-W Orientation = 5%-6% Reduction in Annual Energy Use

Dwg: Building Shape

25

All contain about 8 volume units-

What about surface area?

Enclosure Area to Volume Ratio

Enclosure Area to Volume Ratio

BBD

• Optimized Glazing Design – i.e. windows

sized, configured and oriented to optimize

daylighting, views and solar gain

– Window-to-wall ratio managed to avoid excessive

heat loss while allowing for daylighting and views

– Glazing systems designed to avoid excessive solar

gain – i.e. glass coatings, shadings, etc.

– Use well-insulated & airtight glazing systems

28

29

Window to Wall Ratio

Window-to-Wall Ratio

Assume: Window=U-0.33, Wall=R-15

Window-to-Wall Ratio: 10%

Window-to-Wall Ratio: 50%

Window-to-Wall Ratio: 90%

Critical Barriers

• Water-Shedding Surface Rain Penetration Control

• Water-Resistive Barrier Rain Penetration Control

• Thermal Barrier Thermal Control – Controls conductive and radiant heat flow

• Air Barrier Air Leakage Control – Controls air flow / convective heat flow

• Vapor Barrier Vapor Diffusion Control

34

Critical Barriers

• Water-Shedding Surface Rain Penetration Control

• Water-Resistive Barrier Rain Penetration Control

• Thermal Barrier Thermal Control – Controls conductive and radiant heat flow

• Air Barrier Air Leakage Control – Controls air flow / convective heat flow

• Vapor Barrier Vapor Diffusion Control

35

Critical Barriers

Thermal Barrier

Exterior

Stucco Cladding

Air Space

Sheathing Paper

Exterior Sheathing

Insulated Stud Space

Polyethylene Sheet

Interior Gypsum Board

Interior

Critical Barriers:

Vapor Barrier /Vapor Retarder

Air Barrier

Water Resistive Barrier

Water Shedding Surface

Exterior Interior

Source: RDH Building Sciences

Continuity – A Key Principle

• Continuous barriers are required to achieve

effective thermal and moisture performance

• Continuity of critical barriers must be

provided, not just at field areas, but also at

interface conditions

– Transitions

– Penetrations

– Terminations

37

VAPOR BARRIER

AIR BARRIER

WATER-RESISTIVE BARRIER

WATER SHEDDING SURFACE

AIR BARRIER

VAPOR BARRIER

WATER-RESISTIVE BARRIER

WATER SHEDDING SURFACE

Continuity

Continuity – A Key Principle

• Lack of continuity at critical barriers may result

in:

– Water leakage

– Air leakage

– Thermal bridging

– Condensation

39

Continuity – A Key Principle

• Lack of continuity at critical barriers may result

in:

– Water leakage

– Air leakage

– Thermal bridging

– Condensation

• Leading to:

– Poor energy performance

– Comfort problems

– Durability problems

40

Design of Critical Barriers

• Designer of the building enclosure should be

able to trace the continuity of each critical

barrier through the enclosure system

• Begin with building sections / wall sections

• Continue with foundation, wall and roof details

• Ensure continuity of all five barriers

41

Tracing the

Barriers

42

Thermal

Barrier (TB)

43

Water-shedding

Surface (WSS)

44

Water-resistive

Barrier (WRB)

45

Air Barrier

(AB)

46

Vapor Barrier

(VB)

47

Durability - A Key Principle

• If it doesn’t last very long, it’s not very

sustainable

• Selection and use of durable materials - suited

to the application / exposure - is critical

• Effective enclosure detailing for watertightness,

airtightness and thermal resistance is essential

to achieving both energy performance and

long term durability

48

The Air Barrier

• The air barrier is the system of materials that

controls air leakage / convective heat flow

through the building enclosure

• The air barrier is not one material but instead

is an integrated system of many different

materials/components

49

The Problem of Air Leakage

• Air leakage accounts for 20-40% of the heat

loss through building enclosures…

• Air leakage = higher energy costs

• Air leakage = larger carbon footprint

• Air leakage = reduced water penetration control

• Air leakage = increased condensation risk

• Air leakage = poor airflow control

– Impacts reliability of ventilation system design

50

51

Source: State of Wisconsin Minimium Requirements for the Building Envelope

Air Barrier - Definitions

• Air barriers are defined by their air permeance

• Air Barrier Association of America (ABAA) has taken lead position in developing and promulgating standards

• Now incorporated in many codes - including WSEC

• “Materials” – ≤ 0.04 cfm/sf @ 1.57 psf pressure differential

– ASTM E 2178, Standard Test Method for Air Permeance of Building Materials

52

Air Barrier - Definitions

• “Assemblies” – A collection of air barrier materials and air barrier

components assembled together in a specific manner to create continuity (ABAA)

– ≤ 0.04 cfm/sf @ 1.57 psf

– ASTM E 2357, Standard Test Method for Determining Air Leakage of Air Barrier Assemblies

53

Air Barrier - Definitions

• “System” – An air barrier system is a system of building

assemblies within the building enclosure designed, installed, and integrated in such a manner as to stop the uncontrolled flow of air into and out of the building enclosure (ABAA)

– A whole building air barrier is a system

– ≤ 0.40 cfm/sf @ 1.57 psf

– ASTM E 779, Standard Test Method for Determining Air Leakage Rates by Fan Pressurization

– Alternate standard: ≤ 0.25 cfm/sf @ 1.57 psf (USACE)

54

Air Barrier - Materials

• Exterior cladding

• Sealants

• Flashings (membrane flashing, metal flashing)

• Windows

• Doors (poor AB)

• Housewraps (e.g. Tyvek)

• Wall membranes (e.g. “peel & stick”)

• Roof membranes

• Drywall

• Polyethylene sheet 55

Photo - Air Barrier

56

Air Barrier - Materials

• Material selection criteria includes:

– Air permeance

– Vapor permeance

– Water resistance (if serving as WRB also)

– Cost

– Constructability

– Availability

• Location / placement of air barrier relative to

insulation location is major determinant

57

Air Barrier - Approaches

• Interior Side

– Airtight Drywall Approach

– Sealed Polyethylene Approach

• Exterior Side

– Exterior Sheathing Approach

– Sheathing Membrane Approach (“housewrap”)

• Where cavity insulation approach is used

• Vapor permeable

58

Air Barrier - Approaches

• Exterior Side

– Exterior Sheathing Approach

– Sheathing Membrane Approach (“housewrap”)

• Where cavity insulation approach is used

• Vapor permeable

– Sheathing Membrane Approach (“peel & stick”)

• Where exterior insulation approach is used

• Vapor impermeable

61

Air Barrier - Approaches

• Exterior Side

– Exterior Sheathing Approach

– Sheathing Membrane Approach (“housewrap”)

• Where cavity insulation approach is used

• Vapor permeable

– Sheathing Membrane Approach (“peel & stick”)

• Where exterior insulation approach is used

• Vapor impermeable

– Sheathing Membrane Approach (fluid-applied)

• Vapor permeability dependent on whether cavity

insulation or exterior insulation approach is used

63

Air Barrier - Continuity

• To design and construct a complete air barrier system for the building, continuity must be provided at interfaces between all materials and components…

• Easier said than done!

65

Air Barrier - Continuity

• Key Details for Air Barrier Continuity: – Wall to foundation

– Roof to wall

– Floor lines

– Window and door perimeters

– Other penetrations

– Transitions between wall types

– Transitions between cladding materials

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Airtightness & IAQ

• Mechanical ventilation becomes increasingly important as building airtightness increases

• Effectiveness - and efficiency - of ventilation system becomes more highly critical to ensuring overall building performance, including indoor air quality… – Dedicated fresh air delivery to each space

– Controlled air flow between spaces

– Controlled ventilation rates

– Heat recovery from exhaust air

68

THE THERMAL BARRIER

Can you say “yellow light”?

70

THE THERMAL BARRIER

The Thermal Barrier

• The thermal barrier is the system of materials

that controls conductive and radiant heat flow

through the building enclosure

• Insulation - yes - but many other materials

too…

71

Thermal Barrier Problems

• Thermal Bridges

• Insulation Material Selection

• Insulation Installation Defects

72

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Get your thermal bridge on

74

Thermal Bridging

Thermal Barrier Problems

• Thermal Bridges

• Insulation Material Selection

• Insulation Installation Defects

• Glazing Assemblies

75

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Thermal Barrier Problems

• Thermal Bridges

• Insulation Material Selection

• Insulation Installation Defects

• Glazing Assemblies

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Thermal Bridges

• Exterior Wall Framing Members

– Light gauge steel framing

– Wood framing

80

R-Value Comparison

81 Source: Robert Bombino

Photo - Light Steel Frame Walls

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Thermal Bridges

• Exterior Wall Framing Members

– Light gauge steel framing

– Wood framing

• Regions of Framing “Build-up”

– Exterior Wall Openings (e.g. headers, posts)

– Exterior Wall Corners

– Exterior Wall to Floor Intersections

– Exterior Wall to Roof Intersections

84

Photo: Not so advanced framing…

Other Thermal Bridges

• Window Frames (Aluminum & Steel)

• Metal Subframing at Cladding Systems

• Steel Ledger Angles at Cladding Systems

• Projecting Slab Edges (Concrete)

• Large Structural Framing Members (Steel)

86

Drawing – Straube report

87

Drawing – Straube report

88

Drawing – Straube report

89 Image courtesy of Mike Williams

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Design Overview

Photo Credit: Casey Braunger

Aerial View from South Image courtesy of Ankrom Moisan Architects

First Floor Plan

Image courtesy of Ankrom Moisan Architects

Enclosure Assemblies Images courtesy of Ankrom Moisan Architects

Shading Elements

Balconies

Eyebrows

Image courtesy of William Wilson Architects

HVAC Design

• Highly iterative process

– Design work modeling work costing analysis

constructability review

– Repeat…

• Bidding / procurement

• Coordinating the work…

HVAC Design

• Highly iterative process

– Design work modeling work costing analysis

constructability review

– Repeat…

• Bidding / procurement

• Coordinating the work…

ERV

HEAT

PUMP

Heating & Partial Cooling

Image courtesy of PAE Consulting Engineers

HVAC Design

• Highly iterative process

– Design work modeling work costing analysis

constructability review

– Repeat…

• Bidding / procurement

• Coordinating the work…

Mechanical Penthouse

HVAC Design

• 3 HRV Zones

• Cook ERV serves each zone

HVAC Design

• Continuous 50cfm

supply air per

bedroom

• Continuous

exhaust at kitchen

and bath

• Electric cove

heater in living

room for user

control & backup

heat

- Estimated at 20% of building heating

load • No active cooling at apartments

Image courtesy of PAE Consulting Engineers

R-39

R-40

R-40

R-41

R-48

Coordination Drawing at Typical Exterior Wall to Foundation

Coordination Drawing at Typical Exterior Wall to Roof

Balcony details

Balcony details