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NC-2009 EAp2:Minimum Energy Performance

LPD of Building Area Method

1. If we decides to use 'Building area method' for energy modeling. We have to building area type including office and parking garage. Office baseline model LPD is 1 W/sf and parking garage is 0.3 W/sf. Let's say the office area is 10,000 sqft and parking is 5,000. This gives the total watt 10,000 W + 1,500 W = 11,500 W. Total LPD is 11500/15000 = 0.77 W/sf. Should we model 0.77 W/sf for both parking and office or should we model 1 W/sf for office and 0.3 W/sf. Our project reviewer seems to prefer the 0.77 W/sf approach but we just want to make sure. 2. For the proposed model, we can use the building area method, right? For example, if the building has total lighting watt of 7500 W and the area is 15000 sf. LPD is 0.5 W/sf. Can will use this average LPD in all zones? Thanks Thanks

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Santiago Velez
ASHRAE BEMP HBDP - LEED GA, Building Performance Consultant
Zonda
LEEDuser Basic Member
14 thumbs up

Thu, 08/18/2016 - 15:25

1. I would model 1 W/sf for office and 0.3 W/sf for Parking. Total LPD is for compliance with prescriptive power allowance not for modelling. 2. If you choose Building Area Method, you must use Building area method with the same Building criteria selection for proposed and Baseline and for proposed. So the answer is,Yes, model same LPD all parking, and same LPD in all office zones. That said, in my experience Space by space always gives greater savings than Building Area Method. If you have the option go for that. Best.

Thu, 08/18/2016 - 14:46

Thank Santiago. What do you think Marcus?

Thu, 08/18/2016 - 14:47

Thank Santiago. What do you think Marcus?
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Fri, 08/19/2016 - 15:51

1. Modeling the two spaces with different LPDs is certainly more accurate. If you use 0.77 in all spaces you are shifting internal loads from conditioned to unconditioned spaces. Technically the reviewer is correct but sometimes the rules make no sense and should be slightly bent. This may or may not be a conservative approach. If it is conservative you could try to make that case. 2. You should use the same methodology in both the baseline and proposed models. I agree that the savings is often greater using the space-by-space method. It is also the more accurate way to model most buildings.

Fri, 08/19/2016 - 16:06

Thanks Marcus I found the clear instruction in Advanced Energy Model Guide from USGBC. it clearly said that we have to input LPD of each building area type. We plan to use to response to the reviewer.

Fri, 08/19/2016 - 16:07

Thanks Marcus I found the clear instruction in Advanced Energy Model Guide from USGBC. it clearly said that we have to input LPD of each building area type. We plan to use to response to the reviewer.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Fri, 08/19/2016 - 16:29

Good to know the right way aligns with the guidelines!

Thu, 06/15/2023 - 05:07

Dear Marcus,   If we take a building area method, LPD will same value in all area. However, I'm concered that each rooms internal lighting load.  
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 06/15/2023 - 12:21

It doesn't matter. It only matters if you are trying to "design" the baseline system. It is not designed in the same way as the proposed systems, so again it doesn't matter. Engineers seem to often fall into trying to design the baseline system but it doesn't have to actually operate in reality. That said I think it is far more accurate to use the Space-by-Space Method so if you remain concerned, use that one.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Thu, 06/15/2023 - 12:35

Repeat

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