[Bldg-sim] LEED modeling requirements for existing buildings

Eric O'Neill elo at MichaelsEngineering.com
Thu Aug 14 13:15:32 PDT 2008

Under ASHRAE 90.1 Appendix G, Table G3.1, Section 5, "Baseline Building
Performance" column, requirement (f) (take a breath...) it states that
"For existing building envelopes, the baseline building design shall
reflect existing conditions prior to any revisions that are part of the
scope of work being evaluated". So the rotation doesn't apply to you.
Also, I interpret that to mean the windows don't need to be
redistributed either. Hope that helps!

Eric O'Neill
Mechanical Engineer
Energy Division - Michaels Engineering

811 Monitor St. Ste 100
La Crosse, WI 54603
v: 608-785-1900 x521
f: 608-784-2270
elo at michaelsengineering.com

From: Mark Sorensen [mailto:DEnergyServices at comcast.net] 
Sent: Thursday, August 14, 2008 10:40 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] LEED modeling requirements for existing buildings

When modeling an existing building, is required to calculate the
proposed building window to wall ratio and equally redistribute the
glass area to the baseline building and prepare models for the four
rotation exposures? My take is that for a proposed existing building,
there is not an opportunity to position the building to the most
advantageous exposure and you could end up being penalized if the
baseline energy use is averaged for all rotations but I have not been
able to find any reference in LEED or ASHRAE to support this. I'm not
sure what to think about equal redistribution of the glass areas. 
Mark Sorensen
Diversified Energy Services
5890 E. Pontaluna Rd.
Fruitport, MI 49415

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