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Forum discussion

CS-2009 EAp2:Minimum Energy Performance

Energy modeling Gross Surface / Net surface.

Section 1.2 Space summary in prerequisite EAp2 asks for GrossSquareFootage (GSF) of regularly and unconditioned zones. However, usually the energy model is modeled with net floor area, not gross floor area (i.e. excluding external walls). This means that all surface dependent values are calculated on net floor area (e.g. airflows, fresh air requirements, internal loads, etc..). Which is the correct value for the gross floor area requested by EAp2?Is it only a value calculated by architectural design drawings and not related to the simulation? Regards A

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Marcus Sheffer
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Mon, 04/15/2013 - 13:52

It better be related to the simulation. You can't have a thermodynamically accurate model without the exterior walls! Whether net or gross is reported depends on the software. If using net in Section 1.2 your total square footage should be within 10% of the gross value.

Tue, 04/16/2013 - 14:14

Thank you Marcus. Off course we considered exterior walls, in section 1.2 our problem is that 10% is not enough because it is a Historic Building with 80cm of exteriors wall. We are thinking to describe this situation in the narrative. What do you think?
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Marcus Sheffer
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Tue, 04/16/2013 - 14:39

I do understand your situation. If you are outside the expected 10% or less difference then a narrative explanation would be helpful. Include your calculation values in the narrative.

Mon, 05/06/2013 - 09:10

Hi Marcus, Filling the form for EAp2 Prerequisite this error occurs: "Note: the total building electricity in Table EAp2-10A does not match the proposed total building electricity use in Table EAp2-10. Energy Use Summary.". Total building electricity in Table EAp2-10 accounts for renewable energies (in our case photovoltaics), and it seems that it is not possible to include renewables in Table EAp2-10A. This generates the error above. How Table EAp2-10 and EAp2-10A can match in case of renewables?
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Marcus Sheffer
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Mon, 05/06/2013 - 15:16

Which version of the form are you using?

Mon, 05/06/2013 - 15:17

V03
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Marcus Sheffer
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Mon, 05/06/2013 - 18:40

Got me I do not even see a Table EAp2-10A?

Tue, 05/07/2013 - 11:13

Hi Marcus, Section 1.9A - TOTAL BUILDING PERFORMANCE SUMMARY below there is a Table EAp2-10 - Energy use summary: Total Building energy use performance and following the Table EAp2-10A - Proposed Tenant electricity used.
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Marcus Sheffer
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Tue, 05/07/2013 - 13:45

Now I see it. Since you can't see the calculations it is hard to evaluate these kinds of issues except through trial and error. If you remove the renewable energy use does the error message go away? Since EAp2-10 is calculated and not manually entered perhaps you could try a different method for the renewable calculations and see if it makes the message go away. Sorry I do not have a definite answer.

Tue, 05/07/2013 - 13:50

Ok thanks Marcus, I will try and than i will let you know. A

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