90.1-2010 ECB and PRM questions

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Hello Sim Folks,
I have two questions regarding 90.1-2010 ECB and PRM. Our building code references ECB and LEED references App. G PRM.

Shading due to adjacent buildings ? should this shading be modeled for:
ECB ?
PRM ?

90.1-2010 ECB doesn?t directly refer to shading by other buildings.
App. G as detailed in the PNNL PRM Manual states that external shading from other buildings or other objects can be modeled for 90.1-2010 PRM.

Therefore, I believe one can choose to model that shading or one can ignore it.

Daylighting controls ? should daylighting controls be modeled for:
ECB ?
PRM ?

Re. Daylighting:
Reviewing Section 11.1.4 Compliance with Section 11 will be achieved if:

a. All requirements of Sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4 are met;

Table 11.3.1, 6. Lighting, Baseline: Lighting controls shall be the minimum required.

These clauses lead me to believe that daylighting controls should be modeled in the baseline using the correct side-lighted and top-lighted area calculations.

App. G as detailed in the PNNL PRM Manual is clear ? daylighting controls are to be modeled in the baseline.

Any and all thoughts appreciated.

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

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Dear Chris,
I think the "letter of the law" does not require that you model shading
from an adjacent building for you Baseline.

The "spirit of the law" doesn't seem to *require *it, either. A Baseline
building is intended to be a minimum performance standard against which
your building is compared. For the Proposed building, the owner was not
compelled to select a site with shading from an adjacent building - it
could have been in the middle of a corn field with no shading. As a result,
it seems that you need not include the shading in the Baseline.

It might, however, be beneficial *or *detrimental to include the shading in
the Baseline, and it seems acceptable to do either within the standard's
requirements. I'm imagining a situation where the shading blocks winter sun
and is a net detriment to energy use. If I wanted a rigorous comparison,
I'd make the Baseline model in the manner that gave the lowest Baseline
energy use. If I wanted the most savings :), I'd include the adjacent
building in the Baseline so as not to be penalized.

I agree that the Baseline model must include mandatory requirements for
daylighting.

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Thank you Jim,
I agree with your assessment. If you include shading from adjacent buildings in the proposed, then it should also be included in the baseline. I don?t believe anyone would agree with having shading in one but not the other.

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

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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

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Appendix G-2010 is quite clear on when shading from adjacent buildings should be modeled. From Table G3.1-14:

?All elements whose effective height is greater than their distance from a proposed building and whose width
facing the proposed building is greater than one-third that of the proposed building shall be accounted for in the analysis.?

The baseline is noted as being ?same as proposed?.

Michael Rosenberg

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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

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Thanks for all the input - I'm getting smarter as a result.
Nick, as usual, you're amazing.

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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

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T +1 416-644-0252

2300 Yonge Street, Suite 2300
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It's only an order of magnitude difference; why worry? :)

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