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

[Michael Mantai]

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.