1. NFRC vs. PHI vs. PHIUS Window Certification The full fruit basket?Bronwyn Barry, Assoc. AIA., CPHD Design Director - One Sky HomesJuly 11, 2013 Edited: Feb.26, 2014

2. Three window rating systems now on US market: National Fenestration Rating Council (NFRC): North America based No minimum standards Simulation and Product Test Reqd Passive House Institute (PHI): International Minimum Performance Standard Reqd Simulation only Passive House Institute, US (PHIUS): US based No Min. Performance Reqd Simulation only 3. NFRCs certification criteria: Simulation: 1. Uwindow (required) 2. SHGC (required) 3. Air Leakage (optional) 4. Visible Light Transmittance (optional) (No Min. Performance Reqd.)Verification: 1. Destructive test of window sample 2. Factory inspection Image from NFRC website: http://nfrc.org/fenestrationfacts.aspx 4. PHIs Certification Criteria: 3 Simulation Min. Requirements: 1.Uw = 0.8 W/m2K(0.14 BTU/hrft2F or 6.7 hrft2F/BTU) 2.Uw installed = 0.85 W/m2K3. fRsi =0.7(Varies for other transparent components, including curtain walls, roof domes and skylights. See document: Certification criteria and calculation regulations Passive House Suitable Transparent Components: http://www.passiv.de/downloads/ 03_certification_criteria_transparent_components_en.pdf)Image from PHI component database: http://www.passiv.de/komponentendatenbank/files/pdf/zertifikate/zd_northwin_vision_en.pdf 5. PHIUSs Data Certification Program: Simulation: 1. Uwindow (required) 2. SHGC (required) 3. Air Leakage (optional) 4. Visible Light Transmittance (optional)(No Min. Performance Reqd.)Image from PHIUS info document for window manufacturers Graham Wright 6. How NFRC calcs U-window: UfAfUedge UcogAedgeAcogUcog = U-value glass Acog = Area glass Uf = U-value frame Af = Area frame Uedge = U-value edge of glass Aedge = Area edge of glass Aw = Area Window(Ucog*Acog) + (Uf*Af) + (Uedge*Aedge) Uw = Aw * NFRC requires specific IGU values for each window certification. The U-window value is therefore specific to each certification and makes U-frame values difficult to extract for PHPP use. Thanks to Christian Kohler at LBNL for formula verification. 7. NFRC Therm file protocols: Ucog Boundary Condition: Boundary Condition: NFRC 100-2001 Exterior Temp: -0.4 degF (-18degC) Film Coeff: (Rs) 4.58 BTU/hr.ft2F (26 W/m2K) Emmissivity: 0.84Temp: 69.8 degF (21 degC) Film Coeff: (Rs) 0.39 BTU/hr.ft2F (2.19 W/m2K) (Defined using WINDOW)Uedge Boundary Condition:Temp: 69.8 degF (21 degC) Film Coeff: 0.39 BTU/hr.ft2F (2.1 W/m2K) U-factor Surface: EdgeU-factor Surface: SHGC Exterior (frame exterior only)Uf Boundary Condition:Interior Wood/Vinyl Frame Temp: 69.8 degF (21 degC) Film Coeff: (Rs) 0.43 BTU/hr.ft2F (2.44 W/m2K) U-factor Surface: Frame 8. NFRC simulation sample results:Ucog = 0.13 BTU/hrft2F Uw = 0.14 BTU/hrft2F SHGC = 0.38 VT = 0.51 9. Sample NFRC certificate: Simulation: 1. Ufactor (whole window includes frame + glass) 2. SHGC (specific to each IGU) 3. Visible Transmittance 4. Air Leakage (optional) Verification: NFRC certification requires destructive testing of a sample window and regular factory inspections to achieve full certification. Image from NFRC website: http://nfrc.org/fenestrationfacts.aspx 10. How PHI calcs window U-value For certification: Uf spacer AfUgLg AgUg = U-value glass * Ag = Area glass Uf = U-value frame Af = Area frame spacer = psi L g = Length spacer Aw = Area Window(Ug*Ag) + (Uf*Af) + (spacer*Lg) Uw = Aw * It is important to note that PHI uses a standard IGU rated at 0.123 Btu/hr.ft2F, or 0.7 W/m2K, for all their certification simulations. This generates a U-window (frame + glass) output value, but allows for easy comparison of U-frame values between multiple window profiles. Specific U-glass values are calculated elsewhere in the PHPP for project-specific performance calculation. 11. PHI Therm file protocols: Boundary Condition: Temp: 14 degF (-10degC) Film Coeff: (Rs) 4.35 BTU/hr.ft2F or 0.23 hr.ft2F/BTU (24.69 W/m2K) U-factor Surface: noneUg Boundary Condition:Temp: 68 degF (20 degC) Film Coeff: (Rs) 1.35 BTU/hr.ft2F or 0.74 hr.ft2F/BTU (7.67 W/m2K) U-factor Surface: InteriorUf Boundary Condition:Temp: 68 degF (20 degC) Film Coeff: (Rs) 1.35 BTU/hr.ft2F (7.67 W/m2K) U-factor Surface: Frame * This page verified by Passive House Academy 12. PHI also calculates fRsi*: Exterior: Boundary Condition: Temp: 23 degF (-5degC) Film Coeff: (Rs) 4.35 BTU/hr.ft2F (24.7 W/m2K) (Cursor placed at inside edge of glass and frame) Interior: Boundary Condition: Temp: 68 degF (20 degC) Film Coeff: (Rs) 1.42 BTU/hr.ft2F (4 W/m2K)* This page PHI verified: Benjamin Krick 7.25.13. 13. And Uw Installed: Interior Surface temp difference allowed = 4.2K max. opK = operative temperature (average temp of interior room surfaces and interior air temperature.) aK = (not clear to author at this time requires PHI verification)Uw-installed(Ug*Ag) + (Uf*Af) + (edge*Lg) + (install*Lf) = Aw* This page PHI verified: Benjamin Krick 7.25.13. 14. What is fRsi and Uw, installed ? Passive House Certification is essentially a DURABILITY and COMFORT standard. By including requirements for Uw, installed and fRsi, PHI certification checks against interior drafts and interior surface condensation. This ensures a high level of occupant comfort and the elimination of mold growth.Got Mold?Info from PHI component Certification Criteria document: http://www.passiv.de/downloads/03_certification_criteria_transparent_components_en.pdf 15. PHI Climate Certification Criteria:Only these climate criteria qualify for PHI Certification at this time Image from PHI component Certification Criteria document: http://www.passiv.de/ downloads/ 03_certification_criteria_transparent_comp onents_en.pdf 16. PHI certification example: Uw = 0.75 W/m2K Uw,installed = 0.85 W/m2K Uframe = 0.65 W/m2K Frame width g(spacer) = 0.024 W/mK fRsi = 0.74Certified! Image from PHI component database: http://www.passiv.de/komponentendatenbank/files/pdf/zertifikate/zd_northwin_vision_en.pdf 17. And whats an Efficiency Class? The Passive House Institute recently added a scaled rating (phA+ to phD) to their certificate. It is based on the ratio of glass to frame and favors thinner frames which may have a higher u-value than their wider-framed counterparts.)opaq = g + (Uf x Af)/ LgImages and info from PHI component Certification Criteria document: http://www.passiv.de/downloads/03_certification_criteria_transparent_components_en.pdf 18. How PHIUS calcs window U-value For certification: Uf spacer AfUgLg AgUg = U-value glass * Ag = Area glass Uf = U-value frame Af = Area frame spacer = psi L g = Length spacer Aw = Area Window(Ug*Ag) + (Uf*Af) + (spacer*Lg) Uw = Aw * It appears that PHIUS is using the same simulation protocols as PHI (EN ISO 673, 10077) with outputs structured in a similar format to the NFRC. It also appears PHIUS is calculating specific IGUs for each frame to generate U-window ratings. This info is based on author study of current PHIUS documentation and has not been confirmed by PHIUS. 19. PHIUS Therm file protocols: Boundary Condition: Temp: 14 degF (-10degC) Film Coeff: (Rs) 4.35 BTU/hr.ft2F or 0.23 hr.ft2F/BTU (24.69 W/m2K) U-factor Surface: noneUg Boundary Condition:Temp: 68 degF (20 degC) Film Coeff: (Rs) 1.35 BTU/hr.ft2F or 0.74 hr.ft2F/BTU (7.67 W/m2K) U-factor Surface: InteriorUf Boundary Condition:Temp: 68 degF (20 degC) Film Coeff: (Rs) 1.35 BTU/hr.ft2F (7.67 W/m2K) U-factor Surface: Frame * Simulation protocols are based on the EU ISO 673, 10077 testing protocols. Author assumption. PHIUS has not confirmed. 20. PHIUS Climate recommendations:Image from PHIUS info document for window manufacturers Graham Wright 21. Sample PHIUS certificate: Simulation: 1. Ufactor (whole window includes frame + glass) 2. SHGC (specific to each IGU) 3. Visible Transmittance 4. Air Leakage (optional) 5. U cog 6. SHGC cog (not including frame) 7. Frame widths 8. U-frame values 9. Psi-spacer value Image from PHIUS info document for window manufacturers Graham Wright 22. PHPP inputs required for windows: UfLf UgLgspacer installAfAg U- frame Frame dimensions (width of jambs, header and sill to edge of glass Af ) spacer installation SHGC (or G-value) U-glass 23. What are the differences?Simulation*Req'd Yes Product*Test*Req'd Yes Simulation*Protocol NFRC*100 Includes*specific*IGU* Yes Minimum*UCwindow*Req'd No Min.*fRsi*(Surfac*Temp.*Factr)No Min.*UCInstalled*Req'd NoYes No ISO*10077 3Coptions Yes Yes YesAuthors Evaluation: Fitness Test | TriathlonYes No ISO*10077 Yes No No No | 5K Fun RunSo if you just want to build a Passive House Chart based on most current info publicly available at this time. This chart does not include specific differences between NFRC 100 and ISO 10077, which vary enough to make comparison difficult. Author will revise as new information becomes available. 24. Good luck! (Choose your windows and certifier ahead of time.)Thank You! Questions? Contact: Bronwyn Barry bronwynbarry67 at gmail.com bronwyn at oneskyhomes.com