[Equest-users] 90.1 Baseline Envelope Interpretation

Nick Caton ncaton at smithboucher.com
Tue Feb 7 07:35:49 PST 2012


Hey Daniel,

Hmm - I have never been called out one way or the other regarding existing envelopes under formal review so I can't say with certainty... I'll agree your situation seems tricky!

There's a line within Table G3.1, section 5 baseline column, that also reads "Opaque assemblies used for alterations shall conform with Section 5.1.3."  "Alterations" is a vaguely written glossary term which could be read to apply to your wall upgrades as described.

5.1.3  broadly says all requirements in section 5 for insulation, air leakage and fenestrations apply to the alterations.

Reading that together with G3.1.5.f, your baseline alteration walls should reflect the pre-existing building envelope in every regard, excepting any prescriptive/mandatory requirements of section 5 regarding insulation, air leakage and fenestrations... This assumes none of the 5.1.3 exceptions apply.  This interpretation would permit things like WWR and infiltration rates to differ from the proposed envelope.

I would not advise going hog-wild with differing infiltration rates however.  Garage doors may generally leak more than the proposed construction - but use and document conservative numbers that make sense for an "always closed" door (with weatherseal  if applicable) per the mandatory infiltration requirements.  If you assume the baseline doors are regularly opened by mechanics in the baseline, you're straying from the "same occupants, same scheduling" theme repeated through the rest of Appendix G.

Hope those thoughts help!

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Daniel Kaler
Sent: Monday, February 06, 2012 4:40 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] 90.1 Baseline Envelope Interpretation

Hi All,

I am having trouble fully comprehending ASHRAE 90.1 Appendix G, referring to existing building envelopes. The building I am modeling was previously a maintenance shop with practically zero insulation. In addition to the basic building envelope, the southern facing exposure is essentially 4 large garage doors.

The entire envelope was gutted and replaced with a brick/concrete wall and corresponding insulation. In addition to the envelope upgrade, the entire interior was remodeled to be utilized as an office building. Appendix G leads to me to believe that I should be modeling the building envelope as if the garage doors are still in place. i.e. the offices will have a garage door modeled as the wall type with a significant amount of infiltration. This seems counter-intuitive to me, but I want to verify that I am doing it correctly.

Any input would be helpful, Thanks.

Daniel Kaler
Energy Engineer, EIT


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