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[EnergyPlus_Support] Re: Surface properties:reflectance/absorptance


It looks like you have everything you need. infrared = thermal and i believe in this case you can assume emittance = emissivity (although technically the terms aren't equivalent)

LBNL has an SRI calculator that you could try using by plugging in the "solar reflectance" and "infrared emittance" from the supplier.

coolcolors.lbl.gov/assets/docs/SRI%20Calculator/SRI-calc10.xls

Also, the equation you should use is: 
1 = absorptance + reflectance + transmittance

For an opaque material tranmittance = 0 

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, R- Theru <rtheru@...> wrote:
>
> Hi everyone, 
> 
> I am trying to simulate a layer of concrete tiles coated with cool barrier technology. From a supplier's data sheet on the material's properties, I have data for solar reflectance, NIR reflectance, visible reflectance, UV reflectance, infrared emittance and Solar Reflectance Index (SRI). However, I need to use thermal absorptance (emissivity), solar absorptance and visible absorptance.
> Firstly, am I right in converting solar and visible reflectance to the respective absorptance values by using the formula A=log(1/R)? 
> Secondly, how can I derive emissivity from emittance or the other available data?
> Thanks in advance
>




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