LEED Building Area--Total Footprint or Sum of Rooms?

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I expected to see more on this in the archives.

Is there a consensus on the acceptable floor area to include in a LEED
model? I'll talk as though the building is one story for simplicity. It
seems that floor area is supposed to be consistent across credits, which
leads me toward making the sum of the rooms in the model equal the total
foot print, including all interior and exterior walls, as well as
mechanical chases. However, it seems like a lot of modelers like to just
use the interior floor area of each room, which will obviously total to less
than the total footprint area.

For correct modeling, I can see it both ways. For instance, all of the area
of the exterior surfaces should be accounted for (entire footprint), but
ventilation (in cfm/sf) should just be accounting for usable floor area (sum
of interior room areas). How do others approach this, and what experience
have you had with LEED reviewers?

Thanks,

Christian

Christian Kaltreider's picture
Joined: 2011-09-30
Reputation: 1

Std 90.1 defines the gross floor area to include exterior and interior
walls. A LEED consultant I work with sent the following from the latest
LEED 2009 addendum:

"Gross floor area (based on ASHRAE definition) is that sum of the floor
areas of the spaces within the building, including basements, mezzanine and
intermediate-floored tiers, and penthouses with headroom height of 7.5 ft
(2.2 meters) or greater. Measurements must be taken from the exterior faces
of exterior walls OR from the centerline of walls separating buildings, OR
(for LEED CI certifying spaces) from the centerline of walls separating
spaces. Excludes non-enclosed (or non-enclosable) roofed-over areas such as
exterior covered walkways, porches, terraces or steps, roof overhand, and
similar features. Excludes air shafts, pipe trenches, and chimneys. Excludes
floor area dedicated to the parking and circulation of motor vehicles. (Note
that while excluded features may not be part of the gross floor area, and
therefore technically not a part of the LEED project building, they may
still be required to be a part of the overall LEED project and subject to
MPRs, prerequisites, and credits)."

Note that your lighting allowance is based on the gross floor area.

As for OA, Std 62 defines the zone area as net occupiable, so inside face to
inside face and excludes permanent obstructions such as columns.

Regarding other credits, apparently there is a rule of thumb that the gross
area in EAp2 should be within 7% of the reported gross area used for the
PIFs.

I just went through all this for a LEED project. It's in design review
right now, but this is what they asked for.

ajuran's picture
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Joined: 2011-05-12
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This is good information, Anne. Thanks for responding.

Best of luck with the review!

Christian

Christian Kaltreider's picture
Joined: 2011-09-30
Reputation: 1