Excerpted from LEED 2009 for Retail: Commercial Interiors
To achieve increasing levels of energy conservation beyond the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use.
Demonstrate a 15% reduction in the heat loss and heat gain of the proposed building envelope compared with the baseline building performanceBaseline building performance is the annual energy cost for a building design, used as a baseline for comparison with above-standard design. rating per ANSI/ASHRAE/IESNA Standard 90.1–2007 (with errata but without addenda1) for the building envelope components such as glazing, insulation, roofing, and slab using a modeling protocol or overall UA (U factor x Area) calculation. Projects outside the U.S. may use a USGBC approved equivalent standard2.
Comply with the prescriptive measures for building envelopes of ASHRAE Advanced Energy Design Guide for Small Retail Buildings 2006. The building must meet the following requirements:
1Project teams wishing to use ASHRAE approved addenda for the purposes of this prerequisite may do so at their discretion. Addenda must be applied consistently across all LEED credits.
2 Projects outside the U.S. may use an alternative standard to ANSI/ASHRAE/IESNA Standard 90.1-2007 if it is approved by USGBC as an equivalent standard using the process located at www.usgbc.org/leedisglobal
We have an existing building being renovated. The existing building envelope does not meet ASHRAE 90.1-2007 criteria. If we want to get the credit for EAc 1.5, can we use the existing building envelope as the base line, or do we have to use the building envelope coefficients in ASHRAE 90.1-2007 as the baseline for our model ?
Robert, speaking solely on the basis of my reading of the LEED requirements, I think you would need to use 90.1-2007 as the baseline. There is no mention of a different approach for existing buildings in the credit language, as there is in other LEED rating systems. Also, this is a credit, not a prerequisite, so there is an expectation of strong performance.
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