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Shading by adjacent structures not possible in LEED baseline and E+

asked 2015-03-24 05:01:05 -0500

updated 2015-07-10 06:36:21 -0500

In LEED Energy modelling for EA Credits, it is allowed (not compulsory) to include shading by adjacent structures. This can have an important effect on the results for the proposed building. However, in E+ there is no option to include only the shadowing by adjacent structures for the baseline case. If you remove all external shadowing with MinimalShadowing option, you don't account for adjacent structures. If you choose any other shadowing option, although you may remove all shadowing surfaces from the model, self-shading is always considered, which is not allowed by LEED.

Is there any solution I am not taking into account? The only option I see is to remove shading by adjacent structures, which can affect quite negatively the results from the proposed design.

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So your problem is for the baseline then, where LEED says self-shading cannot be taken into account? Or do they forbid self-shading even for the proposed geometry?

Julien Marrec's avatar Julien Marrec  ( 2015-03-24 07:12:03 -0500 )edit

Yes, the problem is for the baseline (but affects proposed, because if you cannot have it in baseline, you have to remove it also from proposed). They forbid self-shading only for baseline. It is said in 90.1 Appendix G, table 3.1#5: "The builiding shall be modeled so that it does not shade itself".

ecoeficiente's avatar ecoeficiente  ( 2015-03-24 07:36:05 -0500 )edit

Very interesting! What do other engines do in this case?

__AmirRoth__'s avatar __AmirRoth__  ( 2015-03-24 09:47:39 -0500 )edit

eQuest has a keyword (that I have never seen anybody use) attached to the building surfaces (walls, roofs, etc)

SHADING-SURFACE: Accepts code-words YES and NO that tell the program that this exterior surface shades other surfaces. YES causes this EXTERIOR-WALL surface to be considered also as a BUILDING-SHADE surface with TRANSMITTANCE = 0

(note: a roof in eQuest is an EXTERIOR-WALL too...)

Julien Marrec's avatar Julien Marrec  ( 2015-03-25 03:32:11 -0500 )edit

I debated whether to add this as a comment here or on the answer - but the content is the same. With respect the eQuest keyword @Julien Marrec referenced above, I have used this on numerous models that have been submitted for LEED review. This agrees with the interpretation from Nick Caton listed by @macumber below, the baseline walls are not self-shading. Its also the case that all building shading devices in the Proposed model are not included in the Baseline model. I have never directly studied the impact this has on my results, but might be worth studying at some point.

dradair's avatar dradair  ( 2015-05-07 16:29:32 -0500 )edit

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answered 2015-03-24 23:33:27 -0500

If you categorize your shading surfaces into site shading groups (those that are independent of the building) and building or space shading groups (those that are related to the building and rotate when building rotation is applied), then you can easily write a measure to remove one type of shading group but not the other. I think we still need a 90.1 expert to weigh in on if you really cannot model building shading for LEED.

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macumber's avatar macumber  ( 2015-03-24 23:37:03 -0500 )edit

It's one thing to remove attached shading devices, but does the LEED "no self-shading" requirement apply more broadly? A non-convex building can shade itself even without explicit shading devices. Does this effect have to be disregarded too? That seems to require a switch within the application—and a rather tricky one to implement—rather than a tweak to the model. I understand the intent of this provision but it seems so difficult to implement that it's almost not worth pursuing.

__AmirRoth__'s avatar __AmirRoth__  ( 2015-03-25 07:06:45 -0500 )edit

E+ with Minimal Shadowing option does not account for building self-shading. I don't think it should be very difficult to implement external shadowing to the code to cover LEED provision.

ecoeficiente's avatar ecoeficiente  ( 2015-03-26 04:54:53 -0500 )edit

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Asked: 2015-03-24 05:01:05 -0500

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Last updated: Mar 24 '15