I had always understood that inclusion of shading that was under someone else?s control might not be required mainly due to the fact that the proposed building doesn?t know for sure (I think we often have a pretty good idea!) if that structure would remain in place or for what duration of time, whether detrimental or constructive.

That said, the requirement for PRM would be different than if the modeler thought the effect would be large enough that the client should know about it regardless of documenting performance in the official way, then include it.

I?m interested in the inverse situation as well ? this has come up on energy audits more than modeling projects, but sometimes the neighbor is highly reflective and might actually cause more load from reflected sunlight in the opposite position instead of less solar energy via shading from the blocking position.

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

I?m going to jump on to the pile to only add a little more to the ?spirit of the law? discussion. What follows is primarily my opinion and I?m not suggesting any of this is the letter of the law.

Jim?s response pretty succinctly summarizes my position on the matter, but I?ll take one exception (and I concede this is semantic):

I love the word ?rigorous.? It?s a juicy adjective bomb well-suited to drop into any documentation/reporting of my analysis efforts, but it can mean a lot of things to different people (and I acknowledge that). With that setup, to me a ?rigorous? baseline case model pushes towards reality, not in whatever arbitrary direction hinders/helps a performance rating. Rightly stated by others before me, environmental shading and reflective impacts on solar loads can help and/or hinder a building?s actual utility bills through the course of a full set of seasons. Deliberately excluding those effects without extra justification simply doesn?t ring ?rigorous? to me.

It?s fair to note (and I?ve pushed this counter-argument as well): 90.1 Appendix G doesn?t pretend to be ?rigorous? in the sense of matching baselines to actual bills, and to that end I don?t expect a quality LEED model or compliance model to maintain any specific degree of accuracy to reality. I?m not passing any judgement on that front.

But for the above reason, I?m left dissatisfied with the sorts of interpretation that fall back on ?that building may not always be there? because it is actually there and will affect your actual performance (see also discussions on interpreting compliance language for how to handle buildings sharing an envelope wall). In summary, if the modeler is aware of something outside the envelope imparting a substantial impact on the building energy simulation, there?s only one answer as to whether it should be included from a perspective of ?rigor.?

The citation below sets an objective threshold for ?substantial? via height/width/distance proportions. I think it?s a step in the right direction to the extent the authors may be hoping to push 90.1 baselines in the direction of ?reality,? but no succinct passage of that nature will substitute for a modeler becoming spatially aware of the site to determine what ought need to be considered for inclusion in the simulation.

Something I try to impart on others learning to do site walks for energy simulations is to not just look over one shoulder during your perimeter walkaround: Observe the facades, but also what?s going on around the building. Take note of site grading that blocks many hours of direct sunlight, large/substantive tree shading, bodies of water in addition to man-made structures imparting shading or reflected solar loads.

Sorry if this contribution is a little far in the weeds ? I reckon the actual question as pertains to interpretation is pretty well nailed to the wall.

~Nick

[cid:image002.png at 01D2FC9D.C15F77D0]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at schneider-electric.com

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

[cid:image003.png at 01D2FC9D.C15F77D0]

Nick,
?Sorry if this contribution is a little far in the weeds?
We expect nothing less from you ;-)

Re. ?the buildings might not always be there?. My context for asking the question is a building in downtown Toronto. Those specific, tall, adjacent buildings may not always be there but you can expect that whatever replaces them will be tall or taller buildings.

The figure below shows a south facing space on the second floor with and without the shading of adjacent buildings:
[cid:image005.jpg at 01D2FF01.BA0BC770]

Christopher R. Jones, P.Eng.
Technical Specialist
Sustainability & Energy

[cid:image001.png at 01D2FF01.9DE5A9D0]
T +1 416-644-0252

2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4 Canada

wsp.com

Please consider the environment before printing...