[Bldg-sim] Appendix G Interpretation: Existing Building Envelope

Shirish Deshpande shirish at ecpl.co.in
Thu Jun 4 09:38:00 PDT 2009


Dear All,

 

I am proposing the following methodology:

 

·         Prepare a model based on the current envelope and systems and then
to compare them with utility bills for past 12 / 24 months and establish AS
IS case 

 

·         The AS IS case values can be compared with Appendix G values to
establish their status (either %better or %worse than ASHARE base case) and
prepare an baseline.

 

·         The proposed Energy Conservation Measures (ECMs) can be applied to
the AS IS case to calculate % savings

 

 

Shirish M. Deshpande

 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jeremy Poling
Sent: 04 June 2009 19:30
To: Nathan Miller; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Appendix G Interpretation: Existing Building
Envelope

 

Nathan,

 

Your conclusion is the same one I have reached in the past in this situation
– the existing building clause is the overriding factor.  For existing
buildings I interpret that the intent is comparing the proposed model to
what would occur if you did not change anything about the existing building.
It does contradict some of the other provisions of Appendix G, but many of
those provisions seem designed to develop that arbitrary baseline of what
would be considered “minimally compliant” for comparison when a rating
authority uses Appendix G.  It gets even fuzzier when you have an addition
and renovation together since then you have an existing building baseline
for the renovated part of the building and an Appendix G baseline for the
addition.

 

Jeremy R. Poling, LEED AP
Senior Sustainability Analyst
Strategic Services

Site Solutions | Operations | Sustainability

EPSTEIN
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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nathan Miller
Sent: Wednesday, June 03, 2009 7:00 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Appendix G Interpretation: Existing Building Envelope

 

I’ve run into one of those grey areas of the Appendix G language on a
project. We are looking at a major renovation project where the shell of the
building will be upgraded. 

 

Clearly the baseline building will be modeled with insulation U-values that
correspond to the existing conditions of the building rather than the
insulation levels prescribed by tables 5.5-1 to 5.5-8. I think this is
pretty well established.


My question is about the quantity of glazing in each case. For this project
we will be punching new glazing into the existing façade as part of the
renovations. 

 

·         Table G3.1, Section 5 states that “Vertical fenestration areas for
new buildings and alterations shall equal that in the proposed design or 40%
of gross above-grade wall area, whichever is smaller.” So if we add new
windows, it would seem that the baseline building should also have those
windows, but what should their U-value be? Same U-value as the other
existing windows? Lookup the value for new glazing?

·         Lower in that same section of Table G3.1 it states: “Existing
Buildings. 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.” To me, this seems to say that you would
go with the existing quantity of glazing, and the proposed model would have
more glazing than the baseline, even if the proposed does not exceed the 40%
cap.

 

There seems to be a little contradiction between the two requirements. My
inclination is that the existing building clause overrides the requirement
that the same amount of glazing be used in each model. 

 

Have any of you worked on a project where this came up? Any thoughts? It
seems like this could potentially be one of those hot topics of discussion. 

 

Thanks,

 

Nathan Miller, PE, LEED® AP

Senior Energy Engineer/Mechanical Engineer

direct: 206.788.4577

fax: 206.285.7111 

www.rushingco.com <http://www.rushingco.com/> 

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