[Bldg-sim] multiple wall constructions for LEED

Mitchell Dec mdec at glumac.com
Mon Aug 11 14:59:10 PDT 2008

There is likely some confusion due to two statements in the LEED Reference Guide:

*	On Page 177, under "b. Opague Assemblies" the reference guide states "The Performance Rating Method specifies the type of assembly required for the Baseline Building wall, roof, and floor construction. The ECB method varies the construction assembly type modeled in the Building Budget Design based on the actual construction assembly type modeled in the Proposed Design."
*	On Page 180, under "Building Envelope" the reference guide states "The Performance Rating Method requires that the Proposed Design be modeled as designed with a few minor exceptions. For the Baseline Design of new buildings, the above-grade walls, roof, and floor assemblies must be modeled using light-weight assembly types (i.e., steel-framed walls, roof with insulation entirely above deck, and steel-joist floors), with ASHRAE Std. 90.1 prescriptive maximum U-factors for the building's climate. Even if the Proposed Design incorporates mass wall construction, the Baseline Design must be modeled using a steel-framed assembly:"

Obviously, the reference to the ECB Method on page 177 causes some confusion to the reader. However, I read that all building baseline constructions should use a light-weight, steel-framed construction per the statements on page 180.
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Mitchell J. Dec
Senior Energy Analyst
LEED® Accredited Professional



320 SW Washington, Suite 200
Portland, OR 97204-2640
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Thinking. Inside the building.

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org]On Behalf Of Aulbach, John
Sent: Monday, August 11, 2008 2:29 PM
To: Chien Si Harriman; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] multiple wall constructions for LEED

Hi Chien Si !!
I believe you need only put in the one ASHRAE 90.1 minimum wall U-value. Exactly what Table 5.5 asks for.

John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
701 West Kimberly Ave., Suite 245
Placentia, CA 92870-6342 USA
Phone: 714-524-4402
Fax: 714-524-4407
email: jaulbach at nexant.com


From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chien Si Harriman
Sent: Monday, August 11, 2008 2:21 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] multiple wall constructions for LEED

Hi all-
A quick, but kind of hazy question for me at least, regarding LEED projects.  Let's just say, that a building is composed of multiple wall types, spanning a range of the ASHRAE 90.1 definitions...some portions of the building is steel framed, another portion is mass wall, and yet another portion is wood framed, for example.  In this case, what would the baseline be defined as?  Does each wall remain categorically intact, and you simply choose the baseline U-factor that corresponds to that wall type, or do you have to determine the wall type that makes up the majority of the proposed building, and choose this wall type as the baseline wall type?  
Thanks in advance,

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