[Equest-users] Building area method ASHRAE 90.1

[Nick Caton]

Hmm, I think I'm on the fence here.

My practice is identical to Vikram's description for both energy modeling and when documenting compliance for my lighting designs:  Choose whatever method you wish, but always use the same approach for baseline and proposed.  This is pretty clear outside of Appendix G, when documenting compliance.  For modeling, I don't use either approach predominantly - it depends on the project.

Since Patrick is pushing one side, I'll play devil's advocate =):  I can affirm I've used "whole building" averaged LPD in proposed models for successful LEED submission without incident multiple times, documenting that clearly along the way, but I was using "whole building" for the baseline as well in each instance.  I do not personally read 90.1 or LEED to explicitly require LPD be defined with space-by-space for a proposed model.  Patrick, I just checked each of your citations and the only specific call for either method is when the lighting system has not been designed, in which case the whole building approach is prescribed.  Keep in mind both methods should sum to the same total installed watts for the proposed design.

Back to the neutral perspective:  I'll emphasis I do use both approaches.

To Oscar's case:  My general experience has been the whole building method is less generous in net allowable watts when you run the numbers both ways.  In other words, you may stand to earn more LEED points by making your baseline more detailed, using space by space.  My suggestion for Oscar is to simply go with the reviewer's flow and possibly walk away with another point tucked under your arm... it'll probably be a similar amount of effort on your part relative to composing an opposing response, and you won't have to worry about the reviewer disagreeing =).

I agree space-by-space is 'better' for that reason alone - if different at all, it tends to yield a better performance rating.  I will acknowledge space-by-space is also "more accurate," notably so if you're simultaneously defining distinct & accurate lighting schedules space-by-space, but whether the corresponding additional time investment and resulting "accuracy boost" are advantageous for a given LEED model is a toss-up.  I personally feel the role accuracy plays in a LEED model is often overblown to a point of silliness, but that's a personal call we each need to make and a whole 'nother discussion.

Hot related tip:  energy modelers and MEP designers alike need to be aware of COMcheck.  I find it an invaluable time saver for speeding up takeoffs for whole bldg & space by space calcs, and it's only as costly as eQuest.

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick J. O'Leary, Jr.
Sent: Tuesday, May 22, 2012 4:49 PM
To: Sami, Vikram
Cc: eQuest Users; Oscar B.
Subject: Re: [Equest-users] Building area method ASHRAE 90.1

as long as a lighting system has been designed:

according to ashrae/appendix g the uniform/whole building method applies a uniform lpd to the BASELINE building only while the PROPOSED uses what is designed - so long as the design is based on the whole building area method.  the lpd of the PROPOSED design should not be applied uniformly to the PROPOSED building simulation.

see appendix g, table g3.1, section 6 lighting, subsection b, page 173 (2004), page 179 (2007).  user's manual pages g-17/18 (2004 & 2007)

i would suggest to quote table g3.1 when replying to the reviewer's comment.  i have had reviewer's tell me i have to use the space-by-space method in a simulation for both proposed and baseline buildings.  this is not correct.  what is correct is that the simulation reflect the methodology used by the lighting designer.  if the lighting design is based on the whole building method then the whole building method maximum lpd is used in the BASELINE building.  if the design is based on the space-by-space method then the space-by-space maximum lpd for each space type is used in the BASELINE building.  in either case the PROPOSED building should reflect what is designed.  by 'what is designed' i mean look at the lighting plans, lighting schedules, and enter the lpd for each space/zone (thermal block) based on the number of fixtures, watts per fixture, and square feet of space.



On 5/22/12 2:15 PM, Sami, Vikram wrote:
The building area method applies a uniform LPD to the entire building. If you do that in your baseline, you need to apply a uniform LPD to you proposed building too.
In general, I don't recommend using the building are method - the space by space method is a better approach.


Vikram Sami, LEED AP BD+C
Sustainable Design Analyst
1315 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com<mailto:vikram.sami at perkinswill.com>   www.perkinswill.com<http://www.perkinswill.com/>
Perkins+Will.  Ideas + buildings that honor the broader goals of society


From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Oscar B.
Sent: Tuesday, May 22, 2012 4:38 PM
To: eQuest Users
Subject: [Equest-users] Building area method ASHRAE 90.1



How does the building area method work?

I just got a comment from the review team for a project pursuing LEED certification.

I used the building area method for the baseline case and in the proposed case I put the LPD from the lighting design. However they told me that the same method has to be used in both cases.

Any help would be appreciate.




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