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Forum discussion

NC-2009 EAp2:Minimum Energy Performance

LPD

When calculating LPD for the facade (non-tradeable area) can you use the entire facade area or only the actual area being illuminated. Common sense tells me the later but if you read the definition of facade area in ASHRAE 90.1, it includes all of the area shown in an architectural elevation. Thank you.

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Fri, 05/10/2013 - 18:43

Only the area being illuminated. Otherwise the Baseline value would be huge and not in alignment with the Proposed.
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Anil Bhari
Min engineering inc
LEEDuser Basic Member
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Mon, 05/20/2013 - 20:12

Facade is under non-tradable surface, It mean Baseline value should be same as proposed case. so why we have to calculate the LPD for Building facade in baseline. Isn't it baseline Wattage should be same as actual design. Please suggest if i am wrong. Thank you Anil Bhari
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Mon, 05/20/2013 - 20:57

Correct they should be identical in the energy models. The baseline LPD would be calculated for code compliance as this is a mandatory provision. So you do need to calculate the baseline exterior LPD in order to affirm that you comply with this mandatory provision.

Mon, 03/13/2023 - 17:40

Hi everyone, If a facade is partially illuminated and contains a curtain wall that is not directly illuminated but belongs to that facade, should we include the curtain wall area in the calculation? Thanks
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Mon, 03/13/2023 - 19:41

Only the area being illuminated counts.

Tue, 03/14/2023 - 13:19

However, I am still not so sure about it. The ASHRAE 90.1 Users manual declares explicitly: 
If any portion of the facade is illuminated, the allowance is the entire facade area. I believe that includes from the bottom to the top of the facade including the curtain wall area. Can anybody bring some clarity here? Thanks
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LEEDuser Basic Member
3 thumbs up

Tue, 03/14/2023 - 14:18

Lighting design team should have a COMCheck that covers interior and exterior lighting. I use the facade areas from that.
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Marcus Sheffer
LEED Fellow
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LEEDuser Expert
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Tue, 03/14/2023 - 14:21

As indicated in the rest of the thread above, it doesn't really matter. As a non-tradable surface the baseline wattage is identical to the proposed. It only matters for compliance with the mandatory provision. If only a part of the entire facade is illuminated then the issue of compliance is not likely to be in question.
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Cory Duggin
Senior Energy Wizard
TLC Engineering Solutions
LEEDuser Premium Member
44 thumbs up

Tue, 03/14/2023 - 14:40

See example 9-O from the ASHRAE 90.1-2010 user manual.  The entire area of a lit facade is used for the allowance, but as Marcus said, because it is non-tradeable, the baseline and proposed wattage will be the same in the energy model.

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