A90.1 local buildings

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Hi

A quick browse through appendix G doesn't mention local buildings in the
shading. Is it true local buildings aren't considered in the shading calc
for A90?

ta

Chris Yatesv

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My reading of 90.1-2004 does not explicitly disallow external shading
devices. Neither does it clearly define how they might be accounted for
in baseline/proposed models.

The closest thing would be Table G3.1, Section 5. This is clear about
permanent "self-shading" such as overhangs/fins being allowed for the
proposed and not for the baseline. External permanent shading devices
such as local buildings aren't brought up here.

I believe, at the modeler's discretion, local buildings/geographic
features with significant shading effects ought to be considered.
Incorporating these in a manner that preserves the intent of the
"normalized" building orientation for the baseline however could prove
tricky.

First, the location and orientation of such external shading devices
would need to be adjusted for each of the four "turns." For example, a
large skyscraper adjacent to your building's West in the proposed should
move to the building's relative North, East, and South as the building
orientation is adjusted for the baseline.

The second and more thorny point to consider is how to account for that
skyscraper's 2D coordinates relative to the building at each rotation.
I think the most logical route to take would be to maintain the relative
X/Y coordinates from the building footprint's centroid. This however in
some cases might result in one or more of the rotations placing the
skyscraper ON the modeled building. In such a case, you might take an
alternative approach of adding an additional 30 or so degrees to each
rotation, effectively getting a normalized set of results, but avoiding
a physical conflict of location (i.e. instead of 0,90,180,270 orient at
30,120,210,300 from actual). Strictly speaking this would violate
G3.1,5(a) in wording (as it dictates 90, 180,270 from actual), but not
in intent - I would therefore accompany these averaged results with a
written explanation of how such intent is maintained.

A caveat: I haven't tried anything of this sort myself so I am only
speculating at how I would approach this. I'd be very interested to
hear others' experiences with submitting models accounting for permanent
external shading devices under 90.1.

NICK CATON, E.I.T.

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During a EAc1 training seminar put on by the USGBC I distinctly remember
them saying that you shouldn't account for shading from other structures,
there is no way to be sure that the other structure will remain for the life
of the building that you are modeling.

cid:image003.png at 01C9AB43.F0BEE290

Robert Gengelbach, PE, LEEDR AP

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Hello,

Through our experience of a couple of projects, we would suggest that the
project should be credited when there is considerable saving through the
shading of local buildings/structures.
Please find an appropriate view over this issue at:
http://greenbuildinggenie.com/tips/item/13-neighborhood-building-shading

This site seems to be cataloging all such issues as either Hot Tips or Hot
Issue. I find the collection quite informative .

Regards,

Surekha Tetali.

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Hi
I have recently modeled and submitted surrounding building shading effect in
both the proposed and baseline for a commercial campus.
The arguement is that in a campus situation where multiple bldgs are owned
and designed by the same party,shading can be intelligently used to offset
cooling loads and for a building which is shaded by neighbouring buildings
on all sides,simulation results would be considerably different if we
discount the shading.

Hisham

2009/8/4 surekha tetali

--
Regards

Hisham Ahmad

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Yes, I think when you can verify the permanence of the shading structure the
USGBC should be more lenient in the allowing credit for the shading
(especially since the argument is that it may not be there in the future)

cid:image003.png at 01C9AB43.F0BEE290

Robert Gengelbach, PE, LEEDR AP

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Joined: 2011-10-02
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