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Re: [EnergyPlus_Support] Re: U-factor floor in contact with ground





Francesco,

If you know the thermal conductivities (k) of the layers of the floor, and the thickness (L) of those layers, then you can calculate the thermal transmittance (U-Value) for the individual layers as

U = k / L  where U is the thermal transmittance (W/m2-K)  k is thermal conductivity (W/m-K) and L is material thickness (m)

Additionally, the thermal transmittance of the assembly for materials in series is

1 / U (assembly) = 1 / U (layer1) + 1 / U (layer2) ...

Jason



On Sat, Jun 16, 2012 at 4:32 AM, FrancescoP <direzionecontraria@xxxxxxxx> wrote:
 

Thank you for your advice, Jason. I read that part of the Engineering reference.
Therefore if I know the F-factor I can calculate the U-factor or if I know the U-factor I can calculate the F-factor, but how can I do if I know only the dimensions of the building, the thermal conductivity of the soil, thickness and thermal conductivities of the layers composing the slab-on-grade floor?
Best Regards
Francesco Passerini



--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jason Kirkpatrick <jason.alan.kirkpatrick@...> wrote:
>
> Again you should read page 131 of the engineering reference, which gives
> the following in terms of R value
>
> F-Factor x Exposed Perimeter Wall Length / Zone Floor Area =
> Effective U Value
>
> rearranged gives
>
> F-Factor = U-Value x Zone Floor Area / Exposed Perimeter Wall Length
>




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