[Bldg-sim] Existing Envelope for LEED v3

Jones, Christopher cjones at halsall.com
Fri Mar 21 06:56:25 PDT 2014

Just for my own clarity:
You are saying that if the building is a retrofit and the retrofit includes a significantly better envelope, the baseline still uses the pre-existing envelope performance?

Christopher Jones, P.Eng.
Tel: 416.644.4226 * Toll Free: 1.888.425.7255 x 527

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Friday, March 21, 2014 9:25 AM
To: Ken Pilcher; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Existing Envelope for LEED v3

Hi Ken,

Attached is  thread from 9 months back where I reported being corrected to use actual envelope constructions for 3 consecutive projects (reviewed simultaneously), and also to remove baseline rotations.

My understanding since then hasn't altered, though I'm uncertain whether this is spelled out anywhere explicitly with regard to LEED's review policies:  If your building's footprint isn't changing by more than 50%, for modeling purposes at least the project is classified a "retrofit" rather than new construction, and so the guidance/requirements become to match pre-existing envelope constructions for the baseline model (and to not rotate), in accordance with Table G3.1 language on the point.   I haven't run into a similar LEED review scenario since that time however - would be great to hear any others' experiences that would reinforce (or refute) this understanding!
The following CIR (for LEED for homes) evokes the same Table G3.1 language that I think was cited for my case:

Made on: 08/03/2009 | LEED Interpretation

Prerequisite/Credit: EAc1: Optimize Energy Performance
Primary Rating System: Homesv2008

Click here to view the full entry: http://www.usgbc.org/leed-interpretations?keys=2673
Of related interest: LEED at one point made the interpretation of "if you touch it, model minimum baseline requirements instead of existing conditions," but subsequently retracted that interpretation and declared this incorrect.  This is documented here:

Made on: 02/20/2009 | LEED Interpretation

Prerequisite/Credit: EAp2: Minimum Energy Performance
Primary Rating System: NCv2.2

Click here to view the full entry: http://www.usgbc.org/leed-interpretations?keys=5182
I dug up these two CIR's here- you may find a more directly applicable CIR if you've got the time to shuffle through the search results =):  http://www.usgbc.org/leed-interpretations

Best regards,


[cid:489575314 at 22072009-0ABB]


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

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Ken Pilcher
Sent: Thursday, March 20, 2014 11:32 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>; Ken Pilcher
Subject: [Bldg-sim] Existing Envelope for LEED v3

Any help regarding the reuse of an existing building LEED simulation would be helpful. We are working on an existing building that was a warehouse and is now an office building. The existing shell was un-insulated concrete block walls and an un-insulated metal roof with metal joists. Using the ASHRAE 90.1 guidelines for envelope allows the use of existing envelope, but in the climate zone at-hand our proposed envelope alone represents a 30% energy cost savings. Our question is whether there is an exception or limitation to using existing the envelope if a building use is changed, ours is now an office.



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