[Bldg-sim] LEED project - maximum limit allowed to simplified wall azimuth.

Andrew S. Hoover via Bldg-sim bldg-sim at lists.onebuilding.org
Fri Dec 16 06:20:18 PST 2016

Agree with everything you say below.  Reasonably achievable is probably the best, lol.  Just wanted to emphasize getting reasonably achievable is the goal not just getting done.


From: Jim Dirkes [mailto:jim at buildingperformanceteam.com] 
Sent: Friday, December 16, 2016 8:47 AM
To: Andrew S. Hoover <andyhoover at thebestconsultant.com>
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED project - maximum limit allowed to simplified wall azimuth.



Not trying to be difficult here, but it might be better to substitute "reasonable" or "representative" for "accurate". From a certain perspective none of our energy models are accurate. Especially for Appendix G comparisons of new building designs, there are so many variables which are not known with high confidence!


What's the infiltration rate - really?

What is the occupancy or lighting or plug load diversity - really?

What is the part load performance - as installed?



I'm always glad to learn of research which quantifies the impact of topics about which I have a gut check, but don't have time to actually investigate.  The paper Nick cited would be one of them. Those ASHRAE people are also pretty good at doing their homework when writing standards such as 90.1, too.


I ALWAYS attempt to input the best available information, using a good understanding of building science, physics and heat transfer. Nonetheless, I also realize that there are dozens of variables that will not match with actual operation.


p.s., I used 16 facets for my last round tower just to be more confident :)




On Fri, Dec 16, 2016 at 6:12 AM, Andrew S. Hoover via Bldg-sim <bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> > wrote:

Can does not mean you will have an accurate model.  All too often the questions are about what can or what must I do and not about what is best to do.


From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org <mailto:bldg-sim-bounces at lists.onebuilding.org> ] On Behalf Of Leonard Sciarra via Bldg-sim
Sent: Thursday, December 15, 2016 1:05 PM
To: bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> 
Subject: Re: [Bldg-sim] LEED project - maximum limit allowed to simplified wall azimuth.


Julian – 


The text is written to include 45 degrees.  So if they are 45 degrees, then you can make it a square, although the exception was intended for curved surfaces.


Hope this helps.

Leonard Sciarra, AIA, ASHRAE, LEED ap+ 
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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of via Bldg-sim
Sent: Thursday, December 15, 2016 11:17 AM
To: bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> 
Subject: [Bldg-sim] LEED project - maximum limit allowed to simplified wall azimuth.




Does anyone know how to interpret “no more than 45 degrees” of exception 5.b - table G3.1 (90.1-2007/2010/2013) ? : 


5.  Building Envelope

All components of the building envelope in the proposed design shall be modeled as shown on architectural drawings or as built for existing building envelopes. 



b. Exterior surfaces whose azimuth orientation and tilt differ by no more than 45 degrees and are otherwise the same may be described as either a single surface or by using multipliers.


Because “no more than 45 degree” include 45 degree, does the exception still apply if the azimuth of two walls is exactly 45 degrees? 

In other words, considering a LEED project, can a perfect octagonal building shape be modeled as a square building (as long as they have the same floor area and the 8 walls have a similar construction) ?






Julien Dutel, ing., CEM, CMVP.

Direction des secteurs résidentiel, institutionnel et des affaires

Bureau de l'efficacité et de l'innovation énergétiques

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James V Dirkes II, PE, BEMP, LEED AP
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