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Re: [EnergyPlus_Support] Materials U-Value Calculations in E+



Thanks Jean!


I'm doing this. Adapting all the values in design builder to execute the simulation and check if e+ report the values that i'm waiting.


Best regards, thanks for all the answers guys.



De: EnergyPlus_Support@xxxxxxxxxxxxxxx <EnergyPlus_Support@xxxxxxxxxxxxxxx> em nome de Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>
Enviado: sexta-feira, 26 de fevereiro de 2016 03:56
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx
Assunto: Re: [EnergyPlus_Support] Materials U-Value Calculations in E+
 
 

Ivan, e+ calculated "rating values" for the u-value as per ASHRAE 90.1 App. A. The difference is only on the interior and exterior air film convection coeffs. The difference between EU and USA are very small. This is just a rating value. As long as the physical buildup is correct, you are okay, because e+ dynamically calculates the u-values at each simulation step with the step air temperatures which effect the film factors. The rating values are for comparing two assemblies as tested at the same conditions.

That being said, ASHRAE prescribes different methods or tables for constructions derated due to thermal breaks. EU methods are often similar. Absolute annual energy consumption estimates are very similar. For App. G simulations, most reviewers will accept EU ratings on plans and small differences in the e+ reports...possibly because only table 1.4 ever gets checked. If they call it up, a narrative should be able to explain the differences.

Best practice, is to change your input values until the correct rated value is reported by e+.

On 25 Feb 2016 2:23 pm, "Ivan Mezzacapa ivan_slip@xxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
 

Hi everyone, 


I need some help to understand how is the calculation of u-value material in energy plus.


Someone has a spreadsheet that calculates according to the material specifications?

I ask this because I use the design builder to enter the building elements, and saw that the U-value is not the same in EnergyPlus report.

I don't know how energyplus calculate this.

Thanks for all.

Best regards,

Ivan Mezzacapa
Cushman & Wakefield
Energy Efficiency and HVAC Coordinator
 



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Posted by: Ivan Mezzacapa <ivan_slip@xxxxxxxxxxx>


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