A few days ago I got a very interesting email from my new best friend Dan Overbey of Browning Day Mullins Deirdorf Architects. He relayed a story about a client who was building a 16,000 sf horizontally attached addition to an existing 25,000 sf building. The client was committed to sustainable design and was very enthusiastic about pursuing LEED. When BDMD was looking at choosing the appropriate LEED system for their scope, they learned that the project appears to be in a strange LEED 'size gap'.
The core of the problem is that limits on registrations for additions on LEED-NC projects are based on the combined footprint of the existing building + the addition, whereas elgibility for including an addition a LEED-EB certification is based only on the footprint of the existing building... and the two are not mutually exclusive. According to the registration walk-through process on the GBCI website, a project is ineligible for LEED-NC if the scope of work is less than 60% of the total project square footage. Additionally, a project is ineligible for current registration for LEED-EB if the scope of the work is greater than 50% of the existing project square footage:
Dan was kind enough to put together a summary of the issue in this convenient paper... Note that it is possible for a horizontal addition to apply for LEED-NC separately from the existing building if (a) the addition is physically distinct from the original (defined as having party walls separating the space along with separate lighting, HVAC, and plumbing systems) AND (b) the addition has a separate address or name than the existing building. This particular project did not meet those requirements, so they went back to the drawing board.
You may have noticed that I used the phase 'ineligible for current registration' when I mentioned LEED-EB above. Ultimately, the project in question is eligible for LEED-EB, but only after the renovation is complete (the whole facility will be 'existing' at that point), meaning they cannot pick up points for good construction practices under the LEED-EB credits MRc3 and MRc9 Facility Alterations and Additions related credits. It also means that their performance periods cannot begin until the addition is complete, causing a long delay between substantial completion and certification.
To the USGBC and GBCI's credit, they have developed fairly effective tools for helping with system selection. Anyone registering a project for LEED 2009 runs into a sort of registration 'wizard' as part of signing up that helps them select the proper system if they're unsure what to use, and running through the same wizard resulted in a LEED-EB suggestion when I answered these questions with this project in mind. Also, the USGBC has released a LEED Rating System Selection Policy that offers additional guidance, though the issue at hand is not discussed in detail.
Making Something Out of Nothing?
I've been trying to get my head around this issue for days now, and I'm trying to figure out if this is a legitimate problem with the way LEED eligibility is determined or whether this specific instance happens to be a rare outlier and that the USGBC can't be blamed for not covering every construction project imaginable... In my mind no LEED system has really been a great fit for partial (in size) but comprehensive (in scope) renovations or additions, and I'm very curious to hear your thoughts about the subject. Are there others out there that had to go back to their client telling them LEED wasn't an option? Is there a need for a system tailored to renovations that's distinct from LEED-CI but more flexible than LEED-NC? Please share your thoughts by leaving a comment!