[Equest-users] LEED Review Comment on U-Value Input Method

[James Hansen]

Michael, I'd advise that you email the project coordinator (or whatever GBCI calls the "head" of a project review team).  Usually they will answer relatively quick and easy questions so that you don't have to risk improperly addressing a comment.

Ask them where in Appendix G it specifically requires the time delayed method be used.  

GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
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www.ghtltd.com


-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Thursday, June 16, 2011 4:22 PM
To: Michael Mantai; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

Michael,

My understanding has always been that delayed construction should be
used, though I can't find exact wording in Appendix G that requires it
other than G2.2.1(c). For other components/layers of steel-framed walls,
look to A3.3.1, and to Table A3.3 for assembly U-Factors for different
stud spacing. You should be pretty close to the required U-Factor if you
use the correct materials and thicknesses from A3.3. Yes, you may need
to tweak a layer or two to get the construction to match the U-Factor
exactly. As described in other posts, once you create these
constructions for the baseline, copy them for future models.

Regards,
Bill

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael
Mantai
Sent: Thursday, June 16, 2011 4:00 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] LEED Review Comment on U-Value Input Method

We received the following comment on recent LEED review:

"The simulation input screenshots, provided in the EAc1 modeling
narrative
report, indicate that the exterior wall and roof constructions were
modeled
as QUICK surface type (UValue Input specification method), which does
not
account for the timedelayed heat flow through the constructions as
required
by Section G2.2.1(c). Revise the Proposed and Baseline models so the
exterior walls and roof surface types are modeled as DELAYED (Layer
Input
specification method) with the thermal mass effects of the constructions
taken into consideration. In addition, provide a revised LVI report for
each model reflecting the changes."

Section G2.2.1(c) describes modeling software requirements, but I don't
see
anywhere else in Appendix G that specifies that thermal mass effects
have to
be included in the baseline model.

Previous review comments on other projects have led me to believe that
U-value input was the correct method to set up the baseline model.

If I revise the model to input each layer, what layers do I input?
90.1-2007 Appendix G states to use steel-framed walls, and the Tables
provide minimum R-value for insulation and overall assembly U-value.
But it
does not appear to provide such other items as stud spacing, sheathing,
or
even what material is on the outside of the building (for exterior
walls).
Has anyone else had this type of comment before or are you using the
layer
input method for baseline models?  It seems that if I need to specify
layers, the resultant U-value should equal exactly the minimum U-value
per
the 90.1 tables.  That would lead me to believe that there might be
different combinations of layers that result in the same U-values but
result
in different energy use in the baseline, and obviously I would want to
have
the highest energy use for LEED purposes.


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