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Passive House Walls and Windows for the Pacific Northwest
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Design of Durable Walls and Selection of Windows for Passive House Buildings in the Pacific Northwest

Design of Durable Walls and Selection of Windows for Passive House Buildings in the Pacific Northwest

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Passive House Walls and Windows for the Pacific Northwest Presentation Transcript

  • 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 Baseline 2x6 w/ R-22 batts = R-16 effective 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 Stud Concrete Heavy 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 Bullitt Center – Exterior Wall Assembly
  • 23. Bullitt Center – 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) 5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud = R-14.1 effective Crossing Z-girts also evaluated <R-16 effective Intermittent Metal Clips 5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud = R-17.1 effective 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 Bullitt Center – 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 Flange Frame Placement within Opening: In vs Out vs Middle Big difference to ψ install 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 Uframe x 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”) Uglazing x Aglazing ψspacer x L glazed perimeter ψinstall x L window perimeter Uframe x Aframe Uglazing x Aglazing Uedge glz x Aedge glz 2.5” Uedge glz (NFRC) can be converted into a ψedge glz EN/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-value in 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%+) SHGC provided 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" GlasstoWindowAreaRatio 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% WholeWindowSHGC 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 Boundary Condition – W/m2∙K Interior Boundary Condition – 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 CenterofGlazingU-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) ift Rosenheim WA-15/2 Common evaluation criteria: Overall product U-value: 0.8 W/m2∙K Installed product U-value: 0.85 W/m2∙K Different evaluation methods: PHI-D: simulation only, based on “standard” glass with U-value = 0.7 W/m2∙K , computed ψspacer value 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 ψspacer value 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 Glazings and 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 Glazings and 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 Climate Zone Overall Installed Window U- value - Uw Btu/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 exist U-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