Dear All,
In a high rise building we are working on for LEED certification, each
floor has balcony slabs that provide a great deal of shading to the
spaces in the floor below. The balconies circumvent the whole floor
plan. They are part of the passive features to decrease cooling loads.
Would these be considered "shading projections" and not be modeled in
the baseline building? This is what we wish to do, but have doubts
whether the USGBC would reject this modeling approach?
Thank you,
Omer Moltay, LEED AP BD+C, ASHRAE BEMP
I am not sure if LEED has a different interpretation than ASHRAE but the 90.1-2004 and 90.1-2007 user guides go into detail about modeling your scenario slab penetrations for the balconies.
Appendix G Table G3.1.5 specifically states that permanent shading devices may be modeled in the proposed building. The baseline building shall be modeled so that it does not shade itself and no shading projections shall be modeled.
I hope that helps.
Omer,
I would model the balcony slabs in the proposed design but leave them out of the baseline. I do the same thing with canopies over entryways. To be accurate/fair, you should also consider the increased envelope losses through the slabs - this could even be a benefit in a cooling-dominated building.
Regards,
Bill
Dear Omer,
I would model the balcony in both baseline and proposed case as I feel
adding a balcony is more of a functional requirement rather than a shading
requirement. As per ASHRAE the building shall be modeled so that it does
not shade itself, so I would model the balcony but make the self shading
off or heat transmittance as 1.
Regards
Gurneet Singh
If you model the balcony slabs as building shades (how else would you model them?) and set the TRANSMITTANCE = 1 in the baseline "so that it does not shade itself", the modeling results should be the same as if there were no building shades. So you can add building shades for balconies in the baseline (or leave them in if starting from the proposed model) if you want to show them in a 3-D representation, but either way you should not "model" their shading effect in the baseline for LEED/App. G.
Regards,
Bill
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