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

[Jason Kirkpatrick <jason.alan.kirkpatrick@xxxxxxxxx>]

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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