Envelope Design Principles

1. Enclosure Design
Training
AIA Portland
August 2016
Martin Houston
AIA, CSI, LEED AP
Walsh Construction Co.
CLEAResult
Energy Trust of Oregon

2. 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

3. Presentation Outline
• Definitions
• Control Layers
• The Thermal Control Layer
• The Air Control Layer
3

4. Definition:
Water Vapor
Water in it’s gaseous state
4

5. Definition:
Water Vapor
Water in it’s gaseous state
5

6. Definition:
Water Vapor Diffusion
The process by which water vapor spreads or
moves through permeable materials caused
by a difference in water vapor pressure.
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7. 7

8. 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

9. 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

10. Definition:
Condensation
Condensation is the change in the phase of
water from the gaseous phase into liquid
droplets or solid grains .
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12. 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.
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15. 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
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17. 17

18. The Path to Low Energy Buildings
1
2
3
4
18
Basic Building
Design
Enclosure
MEP
On-site Renewable
Energy

19. The Path to Low Energy Buildings
1
2
3
4
19
Basic Building
Design
Enclosure
MEP
On-site Renewable
Energy
Load Reduction

20. 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…

21. The Path to Low Energy Buildings
1
2
3
4
21
Basic Building
Design
Enclosure
MEP
On-site Renewable
Energy
Load Reduction

22. Enclosure – Key Attributes
• Insulation
• Airtightness
• Optimized
Glazing
22

23. 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

25. Dwg: Building Shape
25
All contain about 8 volume units-
What about surface area?

26. Enclosure Area to Volume Ratio

27. Enclosure Area to Volume Ratio

28. 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. 29
Window to Wall Ratio

30. Window-to-Wall Ratio
Assume: Window=U-0.33, Wall=R-15

31. Window-to-Wall Ratio: 10%

32. Window-to-Wall Ratio: 50%

33. Window-to-Wall Ratio: 90%

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
34

35. 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

36. 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

37. 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

38. VAPOR BARRIER
AIR BARRIER
WATER-RESISTIVE BARRIER
WATER SHEDDING SURFACE
AIR BARRIER
VAPOR BARRIER
WATER-RESISTIVE BARRIER
WATER SHEDDING SURFACE
Continuity

39. Continuity – A Key Principle
• Lack of continuity at critical barriers may result
in:
– Water leakage
– Air leakage
– Thermal bridging
– Condensation
39

40. 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

41. 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

42. Tracing the
Barriers
42

43. Thermal
Barrier (TB)
43

44. Water-shedding
Surface (WSS)
44

45. Water-resistive
Barrier (WRB)
45

46. Air Barrier
(AB)
46

47. Vapor Barrier
(VB)
47

48. 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

49. 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

50. 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

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Source: State of Wisconsin Minimium Requirements for the Building Envelope

52. 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

53. 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

54. 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

55. 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

56. Photo - Air Barrier
56

57. 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

58. 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

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
61

63. 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

65. 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

66. 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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68. 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

69. THE THERMAL BARRIER
Can you say “yellow light”?

70. 70
THE THERMAL BARRIER

71. 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

72. Thermal Barrier Problems
• Thermal Bridges
• Insulation Material Selection
• Insulation Installation Defects
72

73. 73
Get your thermal bridge on

74. 74
Thermal Bridging

75. Thermal Barrier Problems
• Thermal Bridges
• Insulation Material Selection
• Insulation Installation Defects
• Glazing Assemblies
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78. Thermal Barrier Problems
• Thermal Bridges
• Insulation Material Selection
• Insulation Installation Defects
• Glazing Assemblies
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80. Thermal Bridges
• Exterior Wall Framing Members
– Light gauge steel framing
– Wood framing
80

81. R-Value Comparison
81
Source: Robert Bombino

82. Photo - Light Steel Frame Walls
82

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84. 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

85. Photo: Not so advanced framing…

86. 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

87. Drawing – Straube report
87

88. Drawing – Straube report
88

89. Drawing – Straube report
89
Image courtesy of Mike Williams

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93. Design Overview
Photo Credit: Casey Braunger

94. Aerial View from South
Image courtesy of Ankrom Moisan Architects

95. First Floor Plan
Image courtesy of Ankrom Moisan Architects

96. Enclosure Assemblies
Images courtesy of Ankrom Moisan Architects

97. Shading Elements
Balconies
Eyebrows
Image courtesy of William Wilson Architects

98. HVAC Design
• Highly iterative process
– Design work  modeling work  costing analysis 
constructability review
– Repeat…
• Bidding / procurement
• Coordinating the work…

99. 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

100. HVAC Design
• Highly iterative process
– Design work  modeling work  costing analysis 
constructability review
– Repeat…
• Bidding / procurement
• Coordinating the work…
Mechanical Penthouse

101. HVAC Design
• 3 HRV Zones
• Cook ERV serves each zone

102. 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

103. R-39
R-40
R-40
R-41
R-48

107. Coordination Drawing at Typical Exterior Wall to Foundation

112. Coordination Drawing at Typical Exterior Wall to Roof

123. Balcony details

124. Balcony details