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Re: [EnergyPlus_Support] Window frame conductance form EU U-Value




mmm...I must have been thinking too much. I'll change that. I think it was only that the film coeff in ISO 15099 are temperature dependant.


2014-05-21 15:27 GMT+02:00 <mailto:farhang.tahmasebi@xxxxxxxxx>farhang.tahmasebi@xxxxxxxxx [EnergyPlus_Support] <<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx>:
>  
Hi all,

> 
> Here is my problem:
> To derive the frame conductance input for EnergyPlus from a frame U-Value calculated based on ISO 10077 (for example 1.4 W/m2.K), I guess it is correct that I only strip off the assumed air film resistance values (0.04 for outdoor and 0.13 for indoor) like this:
> h = 1 / ( 1/1.4 - 0.04 - 0.13) = 1.84 W/m2.K
> Am I right?
> What makes me skeptical is that I read in one DesignBuilder forum that one also needs to consider the boundary condition temperature assumptions in NRC-100 (-18 and 21) and ISO 10077 (0 and 20) like this:
> 
> h = 1.84 * (21-(-18)) / (20-0) = 3.59 W/m2.K
> But, to me this second step does not make sense. Because, as far as I know, the U value is presented based on 1K temperature difference in both methods.
> Do you have any idea on this question?
> Best,
Farhang Tahmasebi
> 
>  




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