Window Standards Compared:

Transcription

1 Window Standards Compared: NFRC, ISO and Passive House Ratings Brittany Hanam M.A.Sc., P.Eng. September 27, 2013

2 Outline North American and Passive House window rating systems Example simulation results What this means and things to be aware of

3 Passive House Windows High performance windows form an integral part of the strategy to achieve whole building energy targets High solar heat gain to offset heating energy Low U-value to reduce heat loss to a point where window becomes a net gain High performance windows provide high interior surface temperatures for thermal comfort & prevent condensation or surface mold growth

4 Requirements for Passive House Windows Component certification vs. building certification PHI offers component certification for windows But windows do not need to be certified by PHI to be used in a Passive House certified building Passive House building requirements for windows: U-value < 0 W/m 2 -K (for comfort) Solar heat gain > 0.50 recommended Other requirements for thermal comfort, hygiene (temperature factor) Overall building energy targets and other requirements Compliance determined via PHPP

5 Requirements for Passive House Windows Passive House component certification criteria for windows Climate specific requirements Performance levels or Efficiency Classes from A+ to D

6 Passive House Windows Component Certification Criteria

7 Passive House Windows Component Certification Criteria E.g. Cool-temperate climate (includes Vancouver, Montreal, Germany) U g 0.75 U W 0 U W,installed 5

8 North American Window Products What are some of the best performing windows available from North American manufacturers? From the ENERGY STAR Canada product database: 326 of 583,120 listings have U ; triples have surface 6 low-e coating and/or Krypton gas fill, or quad glazing Of these listings, highest SHGC is 0.33 How are European manufacturers achieving low U-values with triple glazing, argon gas fill? 0% to 1.0 1% 1.0 to % 1.4 to %

9 Window Rating Standards North America: National Fenestration Rating Council (NFRC) Canada: CSA A440.2 harmonized with NFRC NFRC 100 for U-value, NFRC 200 for SHGC Europe: International Organization for Standardization (ISO) ISO and for frame and whole window U-value EN 673 for glazing U-value EN 410 for glazing solar heat gain (g-value) Passive House ISO standards with some modifications

10 Key Differences Between Window Rating Standards Boundary conditions (temperatures & air film resistances) Standard size of window Method of accounting for edge of glass effects Calculation methodologies (algorithms) for glazing unit airspace, frame U-value SHGC (g-factor) for whole window or centre of glass Treatment of sloped glazing

11 Key Differences: Boundary Conditions U-Value Solar Heat Gain Exterior Temperature Interior Temperature Exterior Temperature Interior Temperature Solar Radiation NFRC -18 o C 21 o C 32 o C 24 o C 783 W/m 2 ISO 0 o C 20 o C 30 o C 25 o C 500 W/m 2 Passive House Frame: -10 o C Glazing: 20 o C to -7 o C 20 o C 30 o C (ISO) Different exterior surface temperatures 25 o C (ISO) 500 W/m 2 (ISO) Note Passive House value for cool-temperate climate is 5 o C, but ISO conditions are acceptable for this climate Different solar radiation Affects solar heat gain calculation Different surface film coefficients

12 Key Differences: Standard Sizes NFRC sizes depend on operator type For example: Fixed: 1.2 m x 1.5 m Tilt & Turn: 1.2 m x 1.5 m Casement Single: m x 1.5 m Passive House has one standard size for fixed and operable punched windows 1.23 m x 1.48 m German operable windows typically Tilt & Turn larger sizes

13 Key Differences: Edge effects Passive House U-Value NFRC U-Value U frame x A frame U frame x A frame ψ spacer x L glazed perimeter 2.5 U edge x A edge U glazing x A glazing U glazing x A glazing ψ install x L window perimeter U frame, ψ spacer, U glazing, ψ install entered into PHPP U frame, U edge, U glazing used to calculate overall U-value

14 Key Differences: Algorithms The NFRC algorithm for centre of glass U-value are more accurate NFRC follows ISO 15099, Passive House follows ISO and EN 673 Footnote in ISO , section 6.2 (reference to EN 673): NOTE The correlations for high aspect ratio cavities [in glazing] used in EN 673 and ISO tend to give low values for the equivalent thermal conductivity. More accurate correlations are given in ISO

15 Key Differences: Solar Heat Gain Passive House g-value: Centre of glass only, does not include frame NFRC SHGC: Value is for whole window, lower to account for frame

16 How do these differences affect energy performance? Study evaluated U-value, solar heat gain of three windows using NFRC and ISO/PHI methods North American Vinyl Frame North American Fibreglass Frame European Vinyl Frame Showed how same product performs under different energy rating systems Each window had same glass, gas fill and spacer

17 Centre of Glazing U-Value Triple glazing, argon gas fill, two low-e coatings 0.9 Big difference between U-values for NFRC and ISO methods and standard temperatures Centre of Glass U-Value, W/m 2 -K 0.7 NFRC, -18 C ISO, 0 C Gap Size, mm

18 Centre of Glazing U-Value Triple glazing, argon gas fill, two low-e coatings 0.9 Differences when only changing exterior temperature of methodology Centre of Glass U-Value, W/m 2 -K 0.7 NFRC, -18 C NFRC, 0 C ISO, -18 C ISO, 0 C Gap Size, mm

19 Centre of Glazing U-Value Triple glazing, argon gas fill, two low-e coatings 0.9 Add in climate-specific temperatures for Passive House certification Centre of Glass U-Value, W/m 2 -K Gap Size, mm NFRC, -18 C NFRC, -7 C NFRC, 0 C NFRC, 5 C ISO, -18 C ISO, -7 C ISO, 0 C ISO, 5 C

20 Centre of Glazing U-Values Examples mm gap: NFRC U-0.72, ISO U mm gap: NFRC U-0.73, ISO U-0.57 Centre of Glass U-Value, W/m 2 -K Gap Size, mm NFRC, -18 C NFRC, -7 C NFRC, 0 C NFRC, 5 C ISO, -18 C ISO, -7 C ISO, 0 C ISO, 5 C

21 Centre of Glazing U-Value Passive House centre of glazing (for window certification) 0.9 Cool-temperate U 0.75 at 0 o C or 5 o C Cold U 0.55 at -3 o C Centre of Glass U-Value, W/m 2 -K Gap Size, mm NFRC, -18 C NFRC, -7 C NFRC, 0 C NFRC, 5 C ISO, -18 C ISO, -7 C ISO, 0 C ISO, 5 C

22 Centre of Glazing U-Values Optimal gap size different for NFRC and ISO 0.9 NFRC optimal gap size is approx. 13 mm ISO optimal gap sizes are larger, approx.18 mm Centre of Glass U-Value, W/m 2 -K Gap Size, mm NFRC, -18 C NFRC, -7 C NFRC, 0 C NFRC, 5 C ISO, -18 C ISO, -7 C ISO, 0 C ISO, 5 C

23 Centre of Glazing U-Values Six IGU configurations were simulated Biggest difference in U-values for larger gap sizes Centre of Glass U-Value, W/m2-K Double glazing mm gaps Triple glazing 12.7 mm gaps Double - High Solar Gain 19% 23% Double - Low Solar Gain 0% 2% Triple - High Solar Gain Triple - Low Solar Gain NFRC ISO

24 Frame U-Values Frame U-Value, W/m 2 2 -K NFRC frame U-values determined with actual IGU and spacer; ISO values determined with calibration panel of specified conductivity lower ISO frame U-values Also different standard material properties, e.g. fibreglass Triple Triple Glazed Glazed North Fibreglass American Frame Vinyl Frame Window Window NFRC 1.2 ISO NFRC 1.0 ISO Fixed - Head Fixed - Sill Fixed - Jamb Fixed - Head 0.4 Fixed - Sill Fixed - Jamb % 2% to 0.0 4% 16% difference Fixed - Head Fixed - Sill Fixed - Jamb 13% to 16% difference Frame U-Value, W/m 2 -K Triple Passive House European upvc Window NFRC ISO

25 Frame U-Values Frame U-Value, W/m 2 2 -K NFRC frame 1.6 U-values determined with actual IGU and spacer; ISO values No determined with calibration panel of specified conductivity lower ISO frame U-values 1.5 Correlation! Also different standard material properties, e.g. fibreglass ISO Frame U-Value Triple Triple Glazed Glazed North Fibreglass American Frame Vinyl Frame Window Window 1.4 NFRC 1.2 ISO NFRC ISO Fixed - Head Fixed - Sill Fixed - Jamb Fixed 1.2- Head 0.4 Fixed - Sill Fixed - Jamb % 2% to 0.0 4% 16% difference NFRC Fixed - Head Frame U-Value Fixed - Sill Fixed - Jamb Frame U-Value, W/m 2 -K Triple Passive House European upvc Window % to 16% difference NFRC ISO

26 Whole Product U-Values Window U-Value, W/m 2 -K ISO U-values generally lower (better) than NFRC U-values but it depends on a lot of factors No Correlation! No conversion factor between ISO and NFRC U-values Window U-Value, W/m 2 -K North American Vinyl Frame Window North American Fibreglass Frame Window 1.2 Fixed Casement Fixed 1.0 Casement Fixed Casement Fixed Casement Double - High Solar Double Low Solar Triple - High Solar Triple - Low Solar Fixed 0.0 Casement Fixed Casement Fixed Casement Fixed Casement Double - High Solar Fixed Tilt Double & Turn- Low Fixed Solar Tilt & Turn Triple - Fixed High Solar Tilt & TurnTriple Fixed - Low Solar Tilt & Turn Dbl: 0% 11% to to 15% 16% Tpl: Trpl: -6% to to 14% 10% Window U-Value, W/m 2 -K Double - High Solar European upvc Frame Window NFRC ISO Double - Low Solar PHI Triple - High Solar PHI Triple - Low Solar NFRC ISO NFRC ISO

27 Whole Product U-Values Window U-Value, W/m 2 -K ISO U-Value ISO 1.6 U-values generally lower (better) than NFRC U-values but it depends on a lot of factors 1.5 No No conversion factor between ISO and NFRC U-values Window U-Value, W/m 2 -K North American Vinyl Frame Window Window U-Value, W/m 2 -K North American Fibreglass Frame Window 1.2 Fixed Casement Fixed Casement Fixed Casement Fixed Casement 1.0 Double - High Solar Double - Low Solar Triple - High Solar Triple - Low Solar Fixed Casement Fixed Casement Fixed Casement Fixed Casement 0.0 Double - High Solar Fixed Tilt Double & NFRC Turn- Low Fixed Solar U-Value Tilt & Turn Triple - Fixed High Solar Tilt & TurnTriple Fixed - Low Solar Tilt & Turn Double: 10% to 16% Triple: -2% to 1% Dbl: 0% 11% to to 15% 16% Tpl: Trpl: -6% 6% to to 14% 10% Correlation! Double - High Solar European upvc Frame Window NFRC ISO Double - Low Solar PHI Triple - High Solar PHI Triple - Low Solar NFRC ISO NFRC ISO

28 Whole Product U-Values Highest percent difference in window U-values was 18% 15% 10% 5% 0% -5% -10% -15% Percent Difference in NFRC & ISO U-Values for Triple Glazed Windows Fixed Operable Fixed Operable ISO rating better North American Vinyl North American Fibreglass European Vinyl NFRC rating better Triple - 180/180 Triple - 366/180

29 Solar Heat Gain Values Solar Heat Gain Coefficient Centre of glass NFRC values were 1% to 8% lower than ISO Greater difference for low solar gain glazing Big difference between centre of glass and whole product values! Fixed: 18% - 19% reduction Operable: 46% - 48% reduction NFRC Centre of Glass ISO Centre of Glass NFRC Fixed SHGC NFRC Operable SHGC 0.0 Double Double Triple - 180/180 Triple - 366/180

30 Summary Biggest Difference? Many differences, but a significant one is centre of glass U-value calculations Centre of Glass U-Values Whole Window U-Values Centre of Glass U-Value, W/m2-K Window U-Value, W/m2-K Double High Solar NA Vinyl Double High Solar NA Vinyl Double High Solar Double High Solar NA Fibreglass EU upvc Double High Solar Double High Solar NA Fibreglass EU upvc Triple High Solar NA Vinyl Triple High Solar NA Vinyl Triple High Solar NA Fibreglass Triple High Solar NA Fibreglass NFRC ISO Triple High Solar EU upvc NFRC ISO Triple High Solar EU upvc

31 Lessons Learned Neither NFRC nor ISO system is better NFRC uses more accurate algorithms, compares all products using the same conditions ISO uses more realistic climate design conditions, important for building energy modeling Today products are optimized to perform best under the rating regimes in effect in Europe, North America Rating regimes drive product design Existing simulation tools have the capability to model North American products for Passive House standards European products will soon need to be rated to NFRC/CSA for Canadian code compliance

32 Moving Forward Be aware that all window ratings are not equal Simply testing to both standards will not help North American manufacturers compete with European product performance due to gap sizes North American manufacturers consider offering larger gap sizes for Passive House projects? North American software can be used with ISO methods Can convert NFRC simulations Other ideas?

33 Thank you! Full report will be available soon at