[Hap-users] Wall Assembly - Steel Stud Framing

Matthew Scott MScott at nefisher.com
Fri Jan 25 10:27:52 PST 2013

Wow, that's kind of alarming to hear. I always assumed the U-value was
more important. I approximate the framing effect by first inputting the
ASHRAE 90.1 assembly for a given wall/roof type, then reduce the R-value
of the insulation (not the other values) until the U-value matches the
value listed in Table A3.3 for the given amount of continuous
insulation. Then I would add in the additional layers of construction
(like brick veneer, block, etc..) that are in the actual design but not
part of the basic ASHRAE tabulated assemblies. 


Matt Scott

N.E. Fisher & Associates, Inc.

329 East Second St, 2nd Flr

Boyertown, PA 19512

e: mscott at nefisher.com

p: 610-369-3190

f: 610-369-3194


From: hap-users-bounces at lists.onebuilding.org
[mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of Michael
Sent: Friday, January 25, 2013 1:01 PM
To: hap-users at lists.onebuilding.org
Subject: [Hap-users] Wall Assembly - Steel Stud Framing


The Wall Properties Input Screen calculates the overall R and U values
for a sandwich assembly however it doesn't have any way to factor in the
"framing effect" of wall studs which can have a significant effect  on
average wall assembly R and U values.


When I queried Carrier, part of Craig's reply was for cooling design
loads and energy modeling, "...U-value is not important, what is
important is making sure the specific heat, density and weight of the
composite insulation/stud layer is correct. Those values are used in the
TFM equations not U-value." 


Since this isn't as simple as inputting an overall U-Value from ASHRAE,
Has anyone come up with a way to effectively model steel stud framing
that would pass a DOE review?




Thank you,


Michael L. Hardy, PE, F.NSPE 
Black Oak Engineering, Inc.
Cell 503.314.5244 


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