Proposal for LEED BD&C 2012

The USGBC’s drafts of proposed changes to their LEED rating systems are open for the first round of public comments. The draft of the 2012 LEED Building Design and Construction includes some significant changes, including some that affect (actually diminish) the role of the building structure in sustainable design. It’s time to act!

As an optimist, I feel that maybe, just maybe, this initiative will lead to the rating system addressing the structure of a building in a meaningful way. In that spirit, I have prepared this – my attempt at pulling together the sustainable aspects of a building structure, and the structural engineer, into the vernacular of the rating system credits.

MR-x: Sustainable Building Structure

(DRAFT, by Jim D’Aloisio, November 2010)

1 Credit (or Prerequisite)

1. Engage the project’s Structural Engineer in the LEED planning charrettes, AND
2. Certify that the building’s structural elements and systems have been efficiently designed to minimize the material use while satisfying the structural and serviceability requirements for their intended purpose, AND
3. Coordinate the foundations and the building superstructure with meeting the requirements of the building envelope insulation and air barrier requirements, including providing details at foundations and slab edges to thermally isolate the interior slab from exterior exposures where appropriate, AND
4. Comply with one or more of the following, as they apply to the project:
   1. For portions of the building where concrete is used for more than five percent of the building structure: Use an average of at least 20 percent reduction of Portland cement in all cast-in-place concrete by use of supplementary cementitious materials, AND Address and minimize or eliminate thermal bridging for any and all concrete elements that extend into or pass across the insulated building envelope.
   2. For portions of the building where masonry is used for more than five percent of the building structure: Use an average of at least 20 percent reduction of Portland cement in all structural masonry units and cementitious grout by use of supplementary cementitious materials.
   3. For portions of the building where wood is used for more than five percent of the building structure: Design, detail, and construct the structural system using Advanced Engineering methodologies to minimize material use and jobsite waste production, and maximize cavity wall insulation opportunities.
   4. For portions of the building where hot-rolled steel is used for more than five percent of the building structure: Address and minimize or eliminate thermal steel bridging for any and all steel elements that extend into or pass across the insulated building envelope.
   5. For portions of the building where cold-formed steel framing is used for more than five percent of the building structure: Detail and construct the exterior building envelope systems to minimize thermal energy loss through the envelope.
   6. For portions of the building where a manufactured, panelized system (including SIPs and precast concrete sandwich panels) is used for more than five percent of the building structure: Coordinate the structural details to ensure insulation and air barrier continuity.
   7. For portions of the building where natural materials, such as straw bale, cob, or rammed earth is used for more than five percent of the building structure: Detail the building so as to minimize long-term degradation due to moisture and other environmental factors.
   8. For buildings with exterior brick, masonry, concrete, or stone cladding: Minimize the potential for thermal building energy loss through ties and anchors.

I’d be very interested in hearing any comments before I finalize this concept and send it to USGBC in late December. What do you think?