[Equest-users] Semiheated envelope constructions

[Mike Karpman]

Hi Ryan,



For most climate zones, your baseline will be a steel-framed wall with R13
cavity insulation. The extra info you’re looking for is available in
Appendix A of ASHRAE 90.1, which describes the assumptions used to come up
with the U-factors in section 5. From outside to inside you have stucco,
5/8” gypsum, framing/insulation layer, 5/8” gypsum (per pg 80 of 90.1 2007).



My modeling process is as follows:



1)      Create a construction in eQUEST with the layers listed above, using
library components.

2)      For the cavity insulation/framing layer, use a DOE-2 library batt
insulation and set the thickness of the insulation layer so that the
R-value of the layer equals the effective R-value of the R13 insulation
between steel studs (R6, per table A9.2B on page 101 of ASHRAE 90.1). (R =
thickness/conductivity)

3)      You can stop here. The U-factor that you see in various places in
eQUEST will differ slightly versus what’s shown in Section 5 of 90.1 (the
difference should be several thousandths... if it’s more than a hundredth
you’ve probably made a mistake). This is due to treatment of air films.
Also, eQUEST stucco is R0.2 while ASHRAE stucco is R0.08. In any case,
reviewers should not complain.

4)      If you are afraid of excessively nitpicky reviewers (which I
believe is a mistake on their part), you can calibrate whatever output
report you’re giving them (such as the LV-D report) to match ASHRAE
exactly. Just adjust the thickness of the insulation layer by the tiny bit
necessary to get the U-values to match. But don’t look at the U-value
reported by the eQUEST interface when you do this, since it doesn’t match
the LV-D report (per notes below).



Note:

-          The U-factors listed in 90.1 include both air-films (per the
definitions section of 90.1 as well as Appendix A)

-          The U-factor shown in the eQUEST interface includes the interior
but not the exterior air-film.

-          The U-factor shown in the eQUEST LV-D report (the summary at the
bottom of this report is a nice place to check when QCing models) includes
both the interior and exterior air-film, assuming 7.5 mph wind



Regards,



Mike Karpman

*Karpman Consulting*

(860) 430-9110

41C New London Turnpike

Glastonbury, CT 06033







*From:* equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Ryan Black
*Sent:* Thursday, September 19, 2013 5:20 PM
*To:* equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Semiheated envelope constructions



I just noticed I left out key information. The tables and categories I
referenced are for ASHRAE 90.1 2007 Appendix G baseline building...



On Thu, Sep 19, 2013 at 1:30 PM, Ryan Black <ryanblack17 at gmail.com> wrote:

I am working on building my first model in eQuest. I have a warehouse that
falls into the semiheated category and I'm wondering how to build the
layers up to reach the given construction U-value. I know that you can
simply hard enter that value, but I've been told it is better to build the
layers. Is this true? And if so, any pointers on how to get the layer
assembly value reasonably close to the table U-values would be greatly
appreciated!



Thanks,



Ryan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130919/92c41912/attachment-0002.htm>