Modeling 90.1 Baseline Envelope for Existing + Additions

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The baseline guidelines might both still apply though, let me throw this interpretation out there. Either way, you should ask for clarification on your proposed path before submitting if possible.

1. Model the existing as-is per the reference that you noted. Seems straightforward.

2. Whole-building totals might still be required to match the 40% and 5%, unless superseded by #1. This seems to be the point of discussion with the reviewer.

In that case the baseline total glazing for the existing portion would be modeled as existing. The new construction baseline would have any remainder of glazing area up to 40%. It sounded like you would be below 40% total, so model as you did before with the basline = proposed.

For skylights the existing building "consumes" more than 5% of the whole project, therefore the skylight area would be capped at whatever the actual percentage is based on the existing. The baseline would not have skylights in the new construction unless they were required to be added by some other part of the code or local requirements in order to meeet the 5% requirement. This could benefit you if the project is adding photocell control of the lighting in the new addition in conjunction with the skylights.

G1.3 is tricky since there is also a new portion to the project that can still impact the overall percentages, even if the existing portion is modeled as-is. And none of the complex is excluded from the renovation, although the envelope may not be changing. Assuming that lighting, HVAC, and interiors are being renovated in the existing warehouse? Otherwise your LEED project boundary should only be the new addition.

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

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David, exactly, that is another way to go. Even if I decide to maintain 40%
and 5% thresholds, there are some different ways of getting there,
considering the mixed existing + addition issue. This is why I agree
requesting some feedback is the way to go.
The existing warehouse was included because is part of the LEED scope and
because it doesn't meet *Table G3.1.2 Additions and alteration to exclude
existing building "c. Design space temperature and HVAC system operating
setpoints and schedules on either side of the boundary between included and
excluded parts of the building are essentially the same."*

Some renovation is happening in the existing bit, lightings is fully
replaced to LED and roof insulation is added. Shading for skylights was
suggested and opted out by the client for various reasons during design. In
the project's weather, 3A, insulations is not as big of an issue as solar
radiation control. So worst case scenario, shading those skylights might be
simple solution to be close to the savings the project was aiming. On the
other hand It is never nice to tell a client you have to add something to
the project once construction has finished, so its worth defending our
approach and our clients interests with reviewers.


2013/11/5 David Eldridge

Santiago Velez

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Joined: 2011-06-07
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