A Taleof Two Rating Systems 20111122 Final

A Tale of Two Rating Systems:NFRC & PHI window testing protocolsApples to apples?Bronwyn Barry, Assoc. AIA., CPHC First draft presented at: Passive House California Mtg. October 23, 2011 Published: Nov.22, 2011

Passive House needs good windows Triple glazing: the new normal? They can be part of your heating system - or not! Image 1: Enersign.de, Image 2: passivehausfenster.at , Image 3: optiwin-usa.com

Windows have pluses and minuses And are complicated! Essence of the PHPP: Heat Demand = Heat Losses – Heat Gains For windows: ‘Loss’ items • Frames • Glazing spacers • Installation edge ‘Gain’ item • SHGC of glass http://passipedia.passiv.de/passipedia_en/planning/calculating_energy_efficiency/phpp_-_the_passive_house_planning_package

How PHPP calculates windows Lf Uf Ug Lg ψspacer Ag ψinstall Af (Ug*Ag) + (Uf*Af) + (ψspacer*Lg) + (ψinstall*Lf)Uw-installed = Aw

Two rating systems now on US market: National Fenestration Rating Council: • US based • No minimum standards • Simulation and product test Passive House Institute: • German based • Set performance standards • Simulation only

PHI’s certification criteria: 1. Uw </= 0.8 W/m2K (0.14 BTU/hrft2F or 6.7 hrft2F/BTU) 2. Uw installed </= 0.85 W/m2K 3. fRsi (temperature factor at edge of glass) (Varies for other transparent components, including curtain walls, roof domes and skylights. See document: Certification criteria and calculation regulations Passive House Suitable Transparent Components Version 1.0 E, 16. May 2011)Image from ENERsign brochure: http://www.qplus-llc.com/index.php?id=1191&L=

NFRC’s certification criteria: Simulation: 1. Uwindow (required) 2. SHGC (required) 3. Air Leakage (optional) 4. Visible Light Transmittance (optional) Verification: 1. Destructive test of window sample 2. Factory inspectionImage from NFRC website: http://nfrc.org/fenestrationfacts.aspx

My comparison sample: Pazen ENERsign Tilt and Turn Jamb profileThis study is based on the simulation results for the ENERsign profile, calculatedby others, using the two testing protocols being compared here.Images from ENERsign brochure: http://www.qplus-llc.com/index.php?id=1191&L=

How PHI calcs window U-value Uf Ug = U-value glass Ug Ag = Area glass Lg Uf = U-value frame ψspacer Af = Area frame Ψspacer = psi Ag L g = Length spacer Af Aw = Area Window (Ug*Ag) + (Uf*Af) + (ψspacer*Lg) Uw = Aw

PHI Therm file protocols: Boundary Condition: Temp: 14 degF (-10degC) Ug Boundary Condition: Film Coeff: (Rs) Temp: 68 degF (20 degC) 4.35 BTU/hr.ft2F Film Coeff: (Rs) or 0.23 hr.ft2F/BTU 1.35 BTU/hr.ft2F or 0.74 hr.ft2F/BTU (24.69 W/m2K) (7.67 W/m2K) U-factor Surface: none U-factor Surface: Interior Uf 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

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 awaiting verification from PHI – TO BE CONFIRMED!

And Uw – Installed: Lf Uf Ug Lg ψspacer Ag ψinstall Af (Ug*Ag) + (Uf*Af) + (ψspacer*Lg) + (ψinstall*Lf)Uw-installed = Aw

PHI Uw testing values: Ug = 0.7 W/m2K Ag = 1.32m2 Uf = 0.675 W/m2K Af = 0.50m2 Ψspacer = 0.0325 W/mK L spacer = 4.62m Aw = 1.82m2 Uf total = (3*Uf jmb+hdr + Uf sill) 4 = (3*0.64 + 0.78) 4 = 0.675 W/m2KImage from: http://passivehouse.com/07_eng/01_dph/HerstLi_e/01Bauw_e/Fenst_e/Daten/D_Pazen_ENERsign.pdf

PHI calculation: (Ug*Ag) + (Uf*Af) + (ψspacer*Lg)Uw = Aw (0.7*1.32) + (0.675*0.5) + (0.0325*4.62) = 1.82 (0.924) + (0.337) + (0.15) = 1.82 = 0.77 W/m2K (or 0.135 BTU/hft2F)

PHI certification for ENERsign: Uw = 0.77 W/m2KImage from ENERsign brochure: http://www.qplus-llc.com/index.php?id=1191&L=

How NFRC calcs U-window: Uf Ucog = U-value glass Uedge Ucog Acog = Area glass Uf = U-value frame Af = Area frame Uedge = U-value edge of Aedge Acog glass Af Aedge = Area edge of glass Aw = Area Window (Ucog*Acog) + (Uf*Af) + (Uedge*Aedge) Uw = AwThanks to Christian Kohler at LBNL for formula verification.

NFRC Therm file protocols: Ucog Boundary Condition: Temp: 69.8 degF (21 degC)Boundary Condition: Film Coeff: (Rs)NFRC 100-2001 Exterior 0.39 BTU/hr.ft2F (2.19 W/m2K)Temp: -0.4 degF (-18degC) (Defined using WINDOW)Film Coeff: (Rs)4.58 BTU/hr.ft2F (26 W/m2K) Uedge Boundary Condition:Emmissivity: 0.84 Temp: 69.8 degF (21 degC) Film Coeff: 0.39 BTU/hr.ft2F (2.1 W/m2K) U-factor Surface: Edge Uf Boundary Condition:U-factor Surface: Interior Wood/Vinyl FrameSHGC Exterior Temp: 69.8 degF (21 degC)(frame exterior only) Film Coeff: (Rs) 0.43 BTU/hr.ft2F (2.44 W/m2K) U-factor Surface: Frame

NFRC simulation results: Ucog = 0.13 BTU/hrft2F Uw = 0.14 BTU/hrft2F

Hidden NFRC Therm outputs: Uf = 0.146 BTU/hrft2F Uedge = 0.161 BTU/hrft2F Ag = 11.6 ft2 Acog = 8.96 ft2 Aedge = 2.65 ft2 Af = 7.7 ft2 Aw = 19.37 ft2

NFRC calculation: (Ucog*Acog) + (Uf*Af) + (Uedge*Aedge)Uw = Aw (0.13*8.96) + (0.146*7.75) + (0.161*2.65) = 19.37 (1.16) + (1.13) + (0.42) = 19.37 = 0.14 BTU/hrft2F (or 0.789 W/m2K)

Agrees with NFRC report: Uw = 0.14 BTU/hrft2F

Where are the differences? Component NFRC PHIWindow size 1.8 m2 1.82 m2Width of frame * 0.15 m 0.1 mDelta T in Therm Boundary condition 39 deg C 30 deg CU-glass 0.73 W/m2K 0.7 W/m2KSpacer vs edge of glass 0.22 W/K 0.15 W/KFinal U-window value (metric) 0.79 W/m2K 0.77 W/m2KFinal U-window value (IP) 0.139 BTU/hr.ft2.°F 0.135 BTU/hr.ft2.°FFinal R-value 7.18 hr.ft2.°F/BTU 7.37 hr.ft2.°F/BTU* Frame size variation is due to different profile options submitted by manufacturer’s representativeto the two testing agencies and is not a protocol difference. Superficially that looks comparable, BUT…

What if we adjust for the differences? (Metric Psi U- units:) Ug Ag Uf Af spacer Lg Aw window 0.7 1.318 0.675 0.5 0.0325 4.62 1.82 PHI 0.9226 0.3375 0.15015 0.775 0.73 1.08 0.675 0.72 1.8 NFRC 0.7884 0.486 0.22 0.830 (Ug*Ag) + (Uf*Af) + (ψspacer*Lg)Uw = Aw (0.7884) + (0.486) + (0.22) = 1.8 = 0.830 W/m2K NFRC results become much more conservative!NFRC test numbers inserted into PHI formula.

Possible solutions?Passive House Institute:• Modify Window Tab in US version of PHPP to account forNFRC simulation protocols• Coordinate simulation protocols with NFRC and allow for‘translation’ by NFRC for PHPP valuesNFRC:• Work with PHI to add PH protocols as another cert. optionOther:• Independent Testing Labs coordinate with PHI to providePHPP performance numbers to US market?

There is still much to do… Let’s figure this out together!Special thanks to:QPlus Llc for use of the ENERsign infoMarles McDonald for NFRC reviewChristian Kohler for NFRC Uw formulaBob Ryan and Passive House Academy for Therm training & reviewThank You! Questions? Contact: Bronwyn Barry bronwynbarry67 at gmail.com bronwyn at oneskyhomes.com

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A Taleof Two Rating Systems 20111122 Final

by Bronwyn Barry on Nov 22, 2011

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A Taleof Two Rating Systems 20111122 Final — Presentation Transcript