Relationship with other existing buildings

Ciao Fabio - You could model the other building to account for the outside the boundary load on the system and then isolate its energy use to only account for your building. Depending on the situation LEED Interpretation 11/2/2004 ID# 5496 EAc1: Optimize Energy Performance NC v2.1 may apply in principle (this was an older CIR we submitted).

90.1-2007 does not require the modeling of the shadows but 90.1-2010 does. So for LEED you do not have to but for accuracy and evaluation you should consider modeling the shadows.

I had one project in the same situation. The chiller is scheduled for two buildings, and COP (100 % - 25 %): 4.55 - 13.20, so in simulation the COP value is always calculated with minimum value 4.55. It is the worst case for energy saving, but I do not need model the other building in the simulation.

I had no problem with the reviewer. This solution is conservative, but good for my project. I did not have any information about the other building and this project had enough points for the target level. If more points were achieved from the EAc1, the project still cannot get the higher level for certification.

Marcus, how have LEED reviewers been handling shading by surrounding buildings on the Baseline?

ASHRAE 90.1-2007 in table G3.1#5(b) prohibits the Baseline building from shading itself (i.e. an L-shaped building) and #5(c) prohibits shading through the use of architectural shading devices or manual window shading devices. However, adjacent buildings are not mentioned in the standard, and I've assumed that if they are modeled in the Proposed Building, they must be modeled in the Baseline as well.

This is furthermore addressed in the LEED EAp2 "Revised Section 1.4 Tables" released in December 2012, where it asks you to put a checkmark by the statement "Any shading by adjacent structures and terrain has been modeled identically to the Proposed case (if applicable)."

Is this a case of USGBC prematurely enforcing 90.1-2010 requirements for LEED 2009 projects, or should we have been doing this all along?

I was thinking you could isolate the other building by metering in the software. You may need to do some post-processing outside the software to fully isolate it. The Interpretation basically allowed up to proportion the load and model the smaller plant for our addition since we wanted to avoid having to model the existing building.

Mark - Including shading from adjacent objects is not required by 90.1-2007 so you would not be asked to include it if you didn't (90.1-2010 requires it). If you did include it, both models should be identical. Since 90.1-2007 is silent on the matter you can do it either way. USGBC is not prematurely enforcing 90.1-2010 in LEED 2009 projects by asking if you modeled it identically.

There is sometimes a difference between good practice and common sense and what is required. It has always been our practice to model adjacent objects that cast the project in a shadow if we determine it will have an impact on energy use. It is a question of accuracy and validity of your modeling results that right now has nothing to do with what is required.

Thanks for your response.

I asked the question because if a Baseline building cannot shade itself, shouldn't it be common sense that adjacent buildings not shade it either. Baseline self-shading was supposedly prohibited to credit Proposed buildings for their form and orientation. By extension, I wondered if the adjacent building shading might be prohibited to credit Proposed buildings for their site selection. Based on ASHRAE and LEED's language, I guess not...

As usual the answer is - it depends!

Adjacent building or even tree shading is more of a fixed component on most projects than self-shading related to design. But it would be interesting if that were a component of site selection.