Page 230 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers
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Requirements
Maintain at least 75% (for LEED 2009 this is either 55%, 75% or 95% for one, two or three points
respectively) (based on surface area) of existing building structure (including structural floor
and roof decking) and envelope (exterior skin and framing, excluding window assemblies and
non-structural roofing material). Hazardous materials that are remediated as a part of the
project scope shall be excluded from the calculation of the percentage maintained. If the project
includes an addition to an existing building, this credit is not applicable if the square footage
of the addition is more than 2 times the square footage of the existing building.
Potential Technologies and Strategies
Consider reuse of existing, previously occupied buildings, including structure, envelope
and elements. Remove elements that pose contamination risk to building occupants and
upgrade components that would improve energy and water efficiency such as windows,
mechanical systems and plumbing fixtures.
(As noted in Table 5.0.0, LEED 2.2 has a now modified MRc1.2 credit for maintaining 95
percent of the existing building structure and envelope.)
Calculations and Considerations (LEED 2009 MRc1.1)
MRc1.1 is not listed with the EB icon, presumably because it is not really applicable for
existing building reviews. This credit is not applicable if there are substantial additions to
the building, totaling more than double the existing gross floor area of the project. If GFA
PEX
is defined as being the gross floor area of the existing building portion of the project which
is to remain and be added on to, and GFA is the proposed total gross floor area of the
P
project, both existing and new, then MRc1.1 cannot be obtained if
GFA > 3 × GFA (5.1.1)
P PEX
It is important to note that the calculations are based on the area of the structural walls
or deckings (floor or roof) and the cladding less the window and door areas. This is
simplified from the LEED-NC 2.1 calculations which had some volume and some area
calculations based on the volume of many structural units and the area of the cladding
items. A simplified summary of how to itemize each of the components is as follows:
• Deckings: Itemize separately the square footage of structural roof decking,
interior floor decking, and the foundation with decking or slab on grade.
Exclude any areas that are considered to be structurally unsound or hazardous
materials. Exclude nonstructural roof surfaces such as asphalt shingle. The total
summation of these can be referred to as STRDECK . The summation of the
T
decking areas that are to be retained can be referred to as STRDECK .
RE
• Exterior walls: Itemize separately each exterior wall area excluding windows
and doors. Exclude any areas that are considered to be structurally unsound or
hazardous materials. The total summation of these can be referred to as
STREXWALL . The summation of the exterior wall areas that are to be retained
T
can be referred to as STREXWALL .
RE
• Interior structural walls: Itemize separately each interior structural wall area
excluding openings, and count only one side of the wall elements for LEED 2009
(both sides were previously counted in LEED 2.2). (It is assumed that the interior
sides of exterior walls are already included in the exterior wall variables.)
Exclude any areas that are considered to be structurally unsound or hazardous
materials. Also, do not include any nonstructural interior wall sections. The total