[Bldg-sim] A90.1 local buildings

[Nick Caton]

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

 

 

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris Yates
Sent: Monday, August 03, 2009 8:33 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] A90.1 local buildings

 

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 Yates

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