Thermal Bridging of Steel Stud Walls

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Hi:
Does anyone know how to calculate the thermal bridging of steel stud walls?? I have a wall with 6" metal studs, 16" OC, with R39 cavity insulation and R10 CI. Table A3.3.3.1 in 90.1-2013 does not go above R21.
Thank you,?Paul Diglio

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Paul,
Chapter 27.5 in the ASHRAE Fundamentals provides examples for calculating the effective R-value for where there is steel studs creating a thermal bridge.

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

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Hi Paul,
Section A9.2(b) directs you to do a parallel path calculation using the modified zone method. The Modified Zone Method for Metal Stud Walls with Insulated Cavities is described in 2017 ASHRAE Handbook ? Fundamentals, p.27.5.
Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP
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Alternately, I use the EE4 modeling program from NRCan. EE4 is a simplified GUI to DOE2.1e. It includes an envelope performance calculator that accounts for different types of thermal bridges. It has many built in materials and you can add custom materials. I use EE4 to establish the envelope performances then I define my eQuest materials and layers to match.

You would have to install EE4 using a virtual machine with XP. It won?t run on 64 bit Windows machines.

https://www.nrcan.gc.ca/energy/software-tools/7453

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

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Thanks Christopher and Bill?Paul Diglio

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