Design objectives, Durability considerations and the Pros & Cons for using alternate highly insulated wall assemblies in the West Pacific Northwest. These include passive design strategies that require airtight and highly insulated walls with minimal thermal bridging to allow for energy efficiency, hygiene (mold/condensation) and thermal comfort. This is in response to a growing desire to apply passive house wall assemblies and windows for houses to taller and more exposed buildings including MURBs. Also, the basic comparison of North American, European and Passivhaus Window rating standards and window selection guidelines. As windows from Europe are rated differently than in North America, passive house guidance from Germany uses European Standards and climate recommendations. The high performance windows provide high interior surface temperatures for thermal comfort and prevent condensation or surface mold growth. This forms an integral part of the strategy to achieve whole building energy targets (ie 4.75 kBtu/sf/y).

1. Passive House Northwest -2013 Annual Conference
Walls and Windows for Highly Insulated Buildings in the Pacific Northwest
Graham Finch, MASc, P.Eng RDH Building Sciences Inc., Seattle, WA

2. Presentation Outline
Design Objectives, Durability Considerations, and the Pros & Cons for Alternate Highly Insulated Wall Assemblies in the Wet Pacific Northwest
Basics of North American, European and Passivhaus Window Rating Standards and Window Selection Guidelines

3. Passive design strategies require airtight & highly insulated walls with minimal thermal bridging
For energy efficiency, hygiene (mold/condensation) and thermal comfort
Effective R-values in range of R-30 to R-60 (depending on climate)
No surface temperatures less than 3oC (5.4oF) below room temperature –for radiant symmetry, comfort, and prevention of condensation or mold
Growing desire to apply passive house wall assemblies & windows for houses to taller and more exposed buildings including MURBs –what are the considerations & risks?
Design Objectives –Passive House Wall Assemblies

4. Thermal insulation continuity –energy & passive design strategy
Airflow control/airtightness –energy & passive design strategy, building code/durability
Vapor diffusion control –building code/durability
Exterior moisture/rainwater control layers & details – building code/durability
More insulation = less heat flow to dry out moisture
Amount, type and placement of insulation matters
Potentially greater sensitivity to vapor diffusion, air leakage, rain water leaks, & built-in moisture
Greater need for more robust assembly designs & details (rainscreen) and more durable materials
Fundamental Requirements

5. What about the Pacific Northwest

6. Climate Zones –Energy Code Classifications
Guides Minimum Insulation levels

7. Climate Zones –Rainfall Exposure
Guides Assembly Choices & Detailing

8. Continue to repair moisture damaged buildings in the Pacific Northwest
Not Passive Houses.. Lower Risk But Still Failed

9. Not Passive Houses.. Lower Risk But Still Failed

10. Definitely Not Passive Houses.. But Still Failed

11. Passive House Performance Level Glazing .. Failed
Systemic Failure of proprietary triple glazing units

12. Rainwater penetration causes most problems –poor details (e.g. lack of, poorly implemented, bad materials)
Air leakage condensation also causes many problems
Vapor diffusion alone contributes but doesn’t cause most problems –unless within a sensitive assembly
Many windows leak and sub-sill drainage and flashings are critical, other details and interfaces also important
Insulation inboard of structural elements decreases temperatures which increases risk for moisture damage
Durability of building materials is very important
Watch over-use of impermeable materials in wet locations
Drained & ventilated rainscreen walls & details work well
Unproven materials/systems can be risky
What Have We Learned from Past Building Failures?

13. Insulation Placement & Wall Design Considerations
Interior Insulation
Exterior Insulation
Split
Insulation

14. Getting to Higher R-values –Insulation Placement
Baseline2x6 w/ R-22 batts = R-16effective
Exterior Insulation –R-20 to R-40+ effective
•Constraints: cladding attachment, wall thickness
•Good for wood/steel/concrete
Deep/Double Stud– R-20 to R-40+ effective
•Constraints wall thickness
•Good for wood, wasted for steel
Split Insulation– R-20 to R-40+ effective
•Constraints: cladding attachment
•Good for wood, palatable for steel
New vs Retrofit Considerations

15. Insulation outboard of structure and control layers (air/vapor/water)
Thermal mass at interior where useful
Excellent performance in all climate zones
Cladding Attachment biggest source of thermal loss/bridging
Not the panacea, can still mess it up
Exterior Insulated Walls
Steel StudConcreteHeavy Timber (CLT)

16. Key Considerations:
Cladding Attachment
Wall Thickness
Heat Control: Exterior Insulation
Air Control: Membrane on exterior of structure
Vapor Control: Membrane on exterior of structure
Water Control: Membrane on exterior of structure (possibly surface of insulation)
Exterior Insulation Assemblies

17. Many Possible Strategies –Wide Range of Performance
Cladding Attachment through Exterior Insulation

18. Minimizing Thermal Bridging through Exterior Insulation
Longer cladding Fasteners directly through rigid insulation (up to 2” for light claddings)
Long screws through vertical strapping and rigid insulation creates truss (8”+) –short cladding fasteners into vertical strapping
Rigid shear block type connection through insulation, cladding to vertical strapping

19. Key Considerations -Split Insulation Assemblies
Key Considerations:
Exterior insulation type
Cladding attachment
Sequencing & detailing
Heat Control: Exterior and stud space Insulation
Air Control: House-wrap adhered/sheet/liquid membrane on sheathing, sealants/tapes etc. Often vapor permeable
Vapor Control: Poly or VB paint at interior, plywood/OSB sheathing
Water Control: Rainscreen cladding, WRB membrane, surface of insulation

20. Split Insulation Assemblies –Exterior Insulation
Foam insulations (XPS, EPS, Polyiso, ccSPF) are vapor impermeable
Is the vapor barrier on the wrong side?
Does your wall have two vapor barriers?
How much insulation should be put outside of the sheathing? –More the better, but room?
Rigid Mineral or Glass Fiber Insulation are vapor permeable and can address these concerns
Vapor permeance properties of WRB and air-barrier also important
Insulation selection suitable for wet exposure –moisture tolerant, non absorptive, hydrophobic, draining

21. Several other alternate strategies to build highly insulated walls including Larsen Trusses and other exterior trussed assemblies filled with low-density fibrous fill or sprayfoam insulation
Split Insulation –Larsen Truss

22. Whole building energy model set a effective R-value design target for ofU-0.055 (R-18.2) for walls, with initial design discussions up to R-25
Expectation to be cost effective, buildable and minimize wall thickness
6” steel stud frame wall structure (supported outboard of slab edge, and perimeter beams)
Were tasked with the evaluation of a number of potential options
Lack of performance from standard practice and available products in 2010 helped develop a new product
BullittCenter –Exterior Wall Assembly

23. BullittCenter –Exterior Wall Assembly Evaluation
Baseline: R-19 batts within 2x6 steel stud with exposed slab edges = R- 6.4 effective
Considered 2x8 and 2x10 studs -still less than R-8
Target >R18.2 effective
w/ potential up to R-25
Vertical Z-Girts (16” oc)
5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud
= R-11.0 effective
Horiz. Z-Girts (24” oc)
14.1 Crossing Z-girts also evaluated <R-16 effective
Intermittent Metal Clips
17.1 up to R-21 with some modifications

24. The Need to Go Higher – Reduce the Thermal Bridging

25. The Need to Go Higher –Reduce the Thermal Bridging
Intermittent Fiberglass Spacers, 3½” to 6” (R- 14 to R-24) exterior insulation
= R-19.1 to R-26.3 + effective

26. Metal panel
1” horizontal metal hat tracks
3 ½” semi-rigid mineral fiber (R-14.7) between 3 ½” fiberglass clips
Fluid applied vapor permeable WRB/Air barrier on gypsum sheathing
6” mineral fiber batts (R-19) between 6” steel studs
Gypsum drywall
Supported outboard slab edge (reduce thermal bridging)
Effective R-value R-26.6
BullittCenter –Exterior Wall Assembly

27. Double 2x4/2x6 stud, Single Deep 2x10, 2x10, I-Joist etc…
Common wood-frame wall assembly in many passive houses
Lends itself well to pre-fabricated wall/roof assemblies
Interior service wall –greater control over interior airtightness
Higher risk for damage if sheathing gets wet (rainwater, air leakage, vapor diffusion)
Double/Deep Stud Insulated

28. Key Considerations –Double Stud/Deep Stud
Key Considerations:
Air-sealing
Rainwater management/detailing
Heat Control: Double stud cavity fill insulation(s)
Air Control: House-wrap/membrane on sheathing, poly, airtight drywall on interior, OSB/plywood at interior, tapes, sealants, sprayfoam. Airtightness on both sides of cavity recommended
Vapor Control: Poly, VB paint or OSB/plywood at interior
Water Control: Rainscreen cladding, WRB at house-wrap/membrane, flashings etc.

29. Air Barrier Strategies –Double Stud/Deep Stud Wall

30. Influenced by Wall Assembly & Structural Support
Type of Window, Rebate vs FlangeFrame
Placement within Opening: In vs Out vs Middle
Big difference to ψinstall
Thermal Performance/ Condensation/ Thermal Comfort
Window Placement within Highly Insulated Walls

31. Highly Insulated Wood-Frame Design Guide for Marine and Cold Climates (tall building/multi-family building focus)
WUFI later
Further Guidance on Highly Insulated Walls & Details

32. Windows for Passive Design
Window Selection Guidelines for Passive Design
North American NFRC , European EN/ISO Window Rating Standards
Climate Specific Window Selection Guidelines

33. Recently completed a large industry research project to look at the validity of the Canadian ER Rating and to evaluate/rank windows in terms of U-values SHGC while also assessing thermal comfort
Differences between North American & European ( and Passive House) window rating systems being studied as part of a follow-up task–Today: What we have uncovered so far…
Understanding Window Rating Systems

34. High performance windows form integral part of strategy to achieve whole building energy target (ie 4.75 kBtu/sf/y)
Provide necessary solar heat gains
Reduce heat loss to a point where window becomes a gain
High performance windows provide high interior surface temperatures for thermal comfort & prevent condensation or surface mold growth
Selection of window properties is climate & building dependant –though general guidelines exist
Windows from Europe are rated differently than in North America –Passive house guidance from Germany uses European standards and climate recommendations
Window Selection for Passive Houses

35. North America –NFRC 100 (U-value) and NFRC 200 (SHGC/VT)
Computer simulation (THERM) using laboratory validated test for calibration/confirmation of model
NFRC 100& 200 are ISO 15099 compliant methods
Europe –ISO 10077-1 (Whole Window U- value), ISO 10077-2 (Frame U-value), EN- 673 (Glazing U-value), EN-410 (Glazing g- value/SHGC)
Passive House Institute Darmstadt (PHI-D) – references ISO 10077, EN 673, EN 410
Plus minimum surface temperature criteria
Window Rating Standards

36. Boundary conditions (temperatures & air film resistances)
Standard size of window
IGU airspace –NFRC vs CEN calculation methodology
Edge of glass vs spacer bar linear transmittance
SHGC (g-factor) for window or just glass
Frame size, thin profile vs thick –ratio of glass to frame
Modeling vs physical laboratory testing
European U-value is not the same as North American U- value –careful in comparisons & in energy modeling
PHI-D guidelines based on European methods not NFRC
Key Differences

37. European vs North American Passive House Window -Typical Differences
European (EU) Style Window
North American (NA) Style Window
Operable Hardware Preference –EU (Inswing) vs NA (Outswing)
EU Frames tend to be deeper (avg. ~4.75”) than NA frames (avg. 2.75”)
EU glazing spacer buried within frame vs inline with NA frame sightline
SAME Argon & SAME low-e emissivity coatings
IGU gap, 1/2” optimum under NA NFRC vs 5/8” optimum under EU CEN/ISO
Why Different?
More standard EU 4mm vs NA 3mm glass panes

38. NFRC vs ISO Window Rating Procedures –U-values
ISO 10077 –European Style Window
NFRC 100 –North American Style Window
Uframex Aframe
Standard Window Size
1.23m wide x 1.48m high (48” x 58 ¼”)
Standard Window Size
1.2m wide x 1.5m high (47 ¼” x 59”)
Uglazingx Aglazing
ψspacer x L glazedperimeter
ψinstall x L window perimeter
Uframex Aframe
Uglazingx Aglazing
Uedgeglzx Aedgeglz
2.5”
Uedgeglz(NFRC) can be converted into a ψedge glzEN/ISO relatively easily (but not vice versa)

39. NFRC vs ISO Window Rating Procedures –Solar Heat Gain
ISO 10077 –European Style Window
NFRC 100 –North American Style Window
g-valuein Europe, SHGC in North America, essentially the same thing, but used differently
g-value provided for center of glass only (neglects frames) (eg. sometimes buried in wall)
Convert to whole window by multiplying by glass/window ratio (becomes lower by 20-40%+)
SHGCprovided for whole window (includes frame effect)
Convert to just glazing by dividing by glass/window ratio (becomes higher by 15-25%+)
Many European glazing manufacturers also use low-iron glass to get the SHGC a few percent higher

40. Passive House SHGC/g-value guidelines are for center of glass,
not including the frames, which reduces the overall SHGC
As NFRC includes this frame impact – a direct comparison in
the SHGC of a Passive House to NFRC window cannot be made,
however perception is that the glass has a higher SHGC .
In PHPP software g-value only applied to glazed area, so
calculation works out.
Following demonstrates the approximate impact
Impact of Frame on Overall SHGC Recommendations
50%
60%
70%
80%
90%
100%
36" x 48" 48" x 60" 60" x 96"
Glass to Window Area Ratio
Window Size
Glass to Total Window Area Ratio - Based on Frame Size
2.75" Frames
(North American
Average)
4.75" Frames
(Passive House
Average)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
60% 65% 70% 75% 80% 85%
Whole Window SHGC
Glass to Window Area Ratio
Approximate Whole Window SHGC Correction of Glass
SHGC Based on Glass to Window Ratio
0.4
0.5
0.6
0.7
0.8

41. Window Rating Standard
Exterior Temperature – oC(oF)
Interior Temperature – oC(oF)
Exterior BoundaryCondition – W/m2∙K
Interior BoundaryCondition – W/m2∙K
NFRC 100 & 200
-18 oC(0oF)
21 oC(70oF)
26.0
2.44 * convection
ISO 10077-1 and 10077-2 and EN 673
0 oC(32oF)
20 oC(68oF)
25.0
7.7
combined
ISO 15099
0 oC(32oF)
20 oC(68oF)
20.0
3.6 *
convection
Passive House Cert. Criteria
-10 oC(14oF)
20 oC(68oF)
25.0
7.7
combined
NFRC vs ISO Window Rating Procedures –Boundary Conditions
For U-value Calculations (Insulated Frames)
This matters because temperature affects air thermal resistance (NFRC/CEN account differently) and interior/exterior air films add thermal resistance directly

42. 0.5
0.6
0.7
0.8
0.9
1.0
7 8 9 10 11 12 13 14 15 16 17 18 19 20
Center of Glazing U-Value (W/m2K)
IGU Argon Space Gap Width (mm)
U-value of Triple Glazed IGU, Cardinal 366 #2, 180 #5 Argon
NFRC 100, -18C
NFRC 100, 0C
CEN 673, -18C
CEN 673, -10C
CEN 673, 0C
Differences in NFRC & CEN on Glass U-values
13 mm (½”) gap:
NFRC (-18oC): U-0.72 (U-0.13)
CEN (0oC): U-0.70 (U-0.12)
16 mm (5/8”) gap:
NFRC (-18oC): U-0.72 (U-0.13)
CEN (0oC): U-0.59 (U-0.10)
Big implications in our climate where 0oC/32oF is winter low average

43. So How Do Some Windows Compare under Each Standard
North American Fiberglass Frame (Double Glazed Reference)
Fixed NFRC Size, 1200 x 1500 mm (47¼” x 59”)
NFRC U-value = 0.266 (0.27 rounded), SHGC 0.534 product
CEN/ISO U-value = 0.233 (0.23 rounded), SHGC 0.667 glass
European Reinforced Vinyl Frame (Triple Glazed)
Tilt & Turn PHI-D Size, 1230 x 1480 mm (48” x 58¼”)
NFRC U-value = 0.149 (0.15 rounded), SHGC 0.371 product
CEN/ISO U-value = 0.140 (0.14 rounded), SHGC 0.538 glass

44. Two European window certification programs
Passive House Institute Darmstadt (PHI-D)
iftRosenheim WA-15/2
Commonevaluation criteria:
Overall product U-value: 0.8 W/m2∙K
Installed product U-value: 0.85 W/m2∙K
Differentevaluation methods:
PHI-D: simulation only, based on “standard” glass with U-value = 0.7 W/m2∙K , computed ψspacervalue
Rosenheim WA-15/2: same as PHI-D, OR by physical testing using actual glass and spacer
Passive House Window Certification Programs

45. Use of real glazing with lower U-value than standard panel provides more accurate evaluation of product performance
Simulations based on glass with U-value = U-0.70 W/m2∙K and computed ψspacervalue require frames with very low U-values to meet whole product evaluation criteria
Testing with actual glass having U-values of 0.5 –0.6 W/m2∙K and real spacer bar shows frames with higher U-values can meet the same whole product evaluation criteria
Lab test results suggest that ISO simulation methods are less accurate for product design purposes, resulting in “overdesign” of window framing members
NFRC simulation methods are more accurate as the results correspond more closely to tested product performance
Interesting Findings about Rosenheim Lab Testing

46. Example –PHI-Darmstadt vs Rosenheim Certified Windows
Same Window Extrusion, Same Manufacturer, Two Product Lines
PHI certified version: Uframe= 0.79 W/m2∙K by computer simulation. The lack of steel reinforcing limits the application of this product in terms of size and resistance to heat distortion (white frame only)
Rosenheim certified version: Uframe= 0.87 W/m2∙K by laboratory testing (guarded hot-box) vs 0.93 W/m2∙K by computer simulation.
Adding steel reinforcing makes this a more versatile and more practical product line (any color, larger frame sizes)

47. Myth: Windows must be PHI-D Certified to be used in certified Passive Houses - FALSE
Window certification and guidance is provided to demonstrate or pre-qualify that certain criteria is met in European Climate Zone: U-value (Frame)
Edge of Glass/IGU Spacer and Window Installation Linear Transmittance (ψ, psi)
Product will meet other passive house criteria including comfort (surface temperature, condensation, hygiene), max 3oC (5.4oF) differential
Passive House Window Myths

48. U-0.8 W/m2∙K (U-0.14 Btu/hr∙ft2∙oF) window criteria, calculated by EN/ISO methods used by PHI-D
Frame U-value as low as possible
Glazing U-value <0.75 W/m2∙K (U-0.13 Btu/hr∙ft2∙oF), under CEN/ISO rating (-10oC)
Triple glazing, 2 low-e coatings (#2/#5), Argon fill
Solar Heat Gain as high as possible (>0.50)
Is as much a comfort requirement (minimum surface temperature) as much as energy
This is based on recommendations for cool-temperate climates (Germany)
BUT –there is actually an underlying climate specific formula which is used: Ug–(Climate Solar Factor)∙ g < 0
European Climate Specific Guidelines for Windows

49. Reference: Passivhaus Institut. 2012. Certification Criteria for Certified Passive House Glazingsand Transparent Components. Darmstadt, Germany.
Passive House Institute (PHI-D) Climate Zones

50. Passive House Institute (PHI-D) Window Guidelines
Reference: Passivhaus Institut. 2012. Certification Criteria for Certified Passive House Glazingsand Transparent Components. Darmstadt, Germany.
Following DOE/ASHRAE Climate Zones (different than above #s), Germany = Zone 5 (referred to as cool-temperate above)
Vancouver*, Seattle & Portland Zone 4 (on warmer side of cool-temperate, but not quite warm-temperature)

51. Passive House Institute (PHI-D) Window Guidelines
Cool U-0.8 (U-0.14, R-7.14)
Warm U-1.25 (U-0.22, R-4.54)
Half Way? U-0.97 (U-0.17 R-5.8) range –interestingly this is the best most high-end N.A. products are

52. PHI-D and Rosenheim certifications for cool- temperate climate (Germany) are not necessarily fixed guidelines for other climate zones
PHIUS has recently developed North American climate specific passive house window U-values and SHGC targets based on ASHRAE/DOE Zones 1-8
North American Passive Window Guidelines

53. PHIUS –Climate Specific Window Selection Guidelines
ASHRAE/DOE North American ClimateZone
Overall Installed Window U- value-UwBtu/hr∙ft2∙oF
Center of Glass U-value -Ug
Btu/hr∙ft2∙oF
SHGC– South
SHGC – North, East, West
8
≤0.11
≤0.10
≥0.50
≤0.40
7
≤0.12
≤0.11
≥0.50
≤0.40
6
≤0.13
≤0.12
≥0.50
≤0.40
5
≤0.14
≤0.13
≥0.50
≤0.40
4
≤0.15
≤0.14
≥0.50
≤0.40
Marine North
≤0.16
≤0.15
≥0.50
≤0.40
Marine South
≤0.22
≤0.20
≤0.50
≤0.30
3 (west)
≤0.18
≤0.16
≤0.50
≤0.30
2 (west)
≤0.18
≤0.16
≤0.30
≤0.30
2(east)
≤0.20
≤0.18
≤0.30
≤0.30
Reference: Table Values PHIUS, Climate Map DOE/ASHRAE/NECB Zones by RDH

54. NFRC and EN/ISO calculate and report window U-values differently and under different conditions (apples vs oranges)
Neither is necessarily better, both have limitations
Procedures exist (LBNL, PHIUS) to calculate NFRC and ISO values from THERM files and vice versa
Careful what values you advertise/brag-about or input into energy models (PHPP is EN/ISO calibrated, most other NA software uses NFRC) –“NFRC values appear conservative, EN/ISO values appear optimistic”
Design for your climate/site/building –guidelines existU-value specification to meet energy target & comfort/surface temperature criteria
SHGC to meet energy target & thermal comfort (but watch overheating without shading)
Conclusions about Passive House Window Selection

55. Discussion
Graham Finch –gfinch@rdhbe.com