[Equest-users] Effective Insulation/Farming Layer R-Value Value

[Nicholas Caton via Equest-users]

I concur with Daniel 100%.

If you really want to run the math however for an odd case, look to Fundamentals (page 27.6 in the 2009 edition) to explore the “Modified Zone Method for Metal Stud Walls with Insulated Cavities.”

~Nick

[cid:image001.png at 01D300AA.308F14C0]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

D  913.564.6361
M  785.410.3317
F  913.564.6380
E  nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>

15200 Santa Fe Trail Drive
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Lenexa, KS 66219
United States

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Daniel Knapp via Equest-users
Sent: Wednesday, July 19, 2017 2:44 PM
To: Morteza Kasmai <morteza.kasmai at gmail.com>
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Effective Insulation/Farming Layer R-Value Value

I would just pick the R-value for insulation (21, 25?) that best matches the R-value of 4 inches of polyurethane spray foam. The depth of the cavity doesn’t make much difference to the end result. If the R-value you’re aiming for isn’t 21, or 25, just interpolate using the numbers in the table. Note that small differences in the R-value don’t make much difference to the effective R-value as thermal bridging has such a strong effect.

—
Daniel Knapp PhD, P Phys, LEED AP
danielk at arborus.ca<mailto:danielk at arborus.ca>

Energy Efficiency Expert
Arborus Consulting
2-43 Eccles Street
Ottawa ON K1R 6S3
(613) 234-7178

On Jul 19, 2017, at 10:16 AM, Morteza Kasmai via Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>> wrote:

There is a wall section in this project with 4” thick interior polyurethane spray foam inside the metal studs.
Since Table A9.2B of ASHRAE 90.1 does not provide the effective insulation/framing layer R-Value for this type of insulation, how can one calculate this value?

Your thoughts and suggestions would be highly appreciated,
Morteza

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