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NC-2009 EAc1:Optimize Energy Performance

Slab-on-grade Vs Slab-below-grade

We have an office building project with garages going 4 storeys underground. The building foundation slab is about 16m deep. Should this slab still be considered for 'slab-on-grade' (even if it is rather 'slab-below-grade') and described by F-factor, or should it be modeled rather as a mass floor, with the U-value adjusted for ground (i.e. as per the EN ISO 13770)?  Thank you, Anna

 

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Marcus Sheffer
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Thu, 05/17/2018 - 14:39

That is not a slab on grade. It gets modeled as a mass floor.

Thu, 05/17/2018 - 18:06

Ok, I will then model as a mass floor characterized by U-value, adjusted for ground. Thanks Marcus

Wed, 05/23/2018 - 12:32

In the xls v2009_Minimum Energy Performance Calculator_v09, tab Opaque Assemblies, there are two entries related to floors: Exposed Floor Construction and Slab-on-Grade floors. 1/ I assume that the Exposed floor construction entry is for floors dividing heated spaces from spaces below (i.e. offices from underground garages). Is the correct? 2/ As discussed above, the underground slab is not slab-on-grade. There is no entry for slab-under-grade in the xls. Should the underground slab then be entered into the Exposed Floor Construction too? 
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Marcus Sheffer
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Wed, 05/23/2018 - 13:06

1. Yes exposed floors separate conditioned and non-conditioned space and also situations where the floor is a part of the exterior exposure. 2. You do not need to provide any input information for the below grade slab.

Wed, 05/23/2018 - 15:40

Thank you for the prompt answer. So then I suppose the logic the same for the below grade walls, if they are not enclosing conditioned space (i.e. no need to enter underground walls, if they are just for garages). Correct?
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Marcus Sheffer
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Wed, 05/23/2018 - 16:21

Correct you only need to include the envelop components that impact the conditioned or semi-conditioned spaces.

Wed, 05/23/2018 - 16:40

Understood, thanks for the support Marcus. Anna

Tue, 10/09/2018 - 16:17

Hi Marcus, One clarification, and one complication. Like Anna I am having some problems filling out the spreadsheet: xls v4_Minimum Energy Performance Calculator_v05, tab Opaque Assemblies, there are two entries related to floors: Exposed Floor Construction and Slab-on-Grade floors. In my case I have essentially a building on a sloped site. On the ground floor the west facade is exposed to the exterior but the east facade underground. There is nothing underneath the ground floor. In this case does it count as a slab-on-grade?  Thanks, Adrian
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Marcus Sheffer
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Tue, 10/09/2018 - 19:51

Yes you have some slab on grade at the west facade.

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