All,
I have learned through informal conversations that modeling site
obstructions from (surrounding buildings) is fine by GBCI, so long as there
is consistency and the same approach is taken in both Baseline and Proposed
models, i.e. either both models include surrounding buildings, nor neither
does.
Is there a CIR or other reference anyone is familiar with which records
this guidance, which can be cited?
Thanks.
*Arpan Bakshi** *LEED AP BD+C, ESTIDAMA PQP
Arpan,
The 90.1-2007 User's Manual clearly states (page G-15):
"Shading of the building by surrounding structures and topography should be modeled identically in both the proposed and baseline buildings."
Which confirms what you have grasped.
Regards,
[cid:image004.jpg at 01CE2576.B915B7E0]Demba Ndiaye, Ph.D., P.E., LEED AP BD+C, BEMP
Demba, unfortunately, the User's Manual cannot be used as the word of the
rating authority. It would need to be cited somewhere in the Standard, or
in a ruling by the GBCI.
*Arpan Bakshi** *LEED AP BD+C, ESTIDAMA PQP
Arpan,
The User's Manual seeks to explain the intent of the Standard. I see no wording related to neighboring buildings in the applicable sections of the Standard, meaning it does not regulate this aspect, and consequently the Baseline should not be penalized if deciding to model neighboring building effects.
Arpan & others:
In my experiences with the LEED reviewership (your mileage may vary), I have found the User's manual to be at least as solid a source for citation as the 90.1 Standard itself, for a variety of topics. If I recall correctly, reviewers have in fact cited the User's Manual on occasion within their commentary.
I have not as of yet attempted modeling adjacent buildings or other permanent shading elements for a LEED submission, but it seems the User's Manual is clear enough: model any such remote shading sources identically in both models, if at all. An extra nuance to consider however is how you handle the baseline rotations (assuming LEED-NC here) in regards to those exterior elements... I would be sure to touch on that for your EAp2 documentation. Intuitively, I would expect such elements should not rotate with the building, in the spirit of substantiating the "site orientation" decision-making, which may (or may not) require some additional legwork beyond the usual simple baseline parametric runs.
IF such shading demonstrates a legitimate improvement in the proposed design relative to the baseline averages (I wouldn't count on it for all cases), AND the shading sources in question are at least as permanent as the building itself (i.e. other buildings, a sheer cliff face, etc. - something more transient like trees/foliage I would feel dubious about) I'd give it a shot, with care to document your procedure very clearly, including the User's Manual citation.
Worst case scenario: Reviewer tells you to remove them in their technical advice - live & learn (and let us know!) ;)
Regards,
~Nick
[cid:489575314 at 22072009-0ABB]
NICK CATON, P.E.
Good morning, all,
The ASHRAE User's Manuals are generally well accepted supplements to the
standards and should be uses as long as its guidance does not directly
contradict the standard or official guidance offered by GBCI in the form of
interpretations. You should look at ASHRAE 90.1-2010. I believe a new
section to Table G3.1 (#14) which describes the modeling protocol for
shading from site features. I am not certain if this was an addendum item
for 90.1-2007. If it is, you should indicate which addendum you are
applying. If not, you should just indicate what guidance you are following
and cite the more recent version of the standard. If you follow this
guidance you should be fine.
Hope this helps.
Cam Fitzgerald
Good day,
For me it seems obvious that if you are going to include an adjacent building in your energy model you should include it in both baseline and proposed designs. Table G3.1-14 of the Appendix G of ASHRAE 90.1 2010, as Cam mentions, describes this. But what if the adjacent building is not yet constructed but it will be in a 5-year period after the completion of the building that is being LEED certified. Should we include it in the model? In this particular case I am describing, the future building will be place south of the first one and it is located in a very hot area (5721 CDD10 C), so this will reduce in great amount the solar heat gains. I am not sure what to do, thinking about the lifetime of the building, 5 years is nothing.
Any suggestions would be greatly appreciated.