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Re: [EnergyPlus_Support] SRI/Refelectivity study



I wonder how they are converting from reflectivity and emissivity to solar & thermal absorbance in this E+ interface.  .http://coolroof.cbs.iiit.ac.in/calculator_detailed.html 




Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions
120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951
  






On Thu, Oct 4, 2012 at 12:23 PM, Javed Iqbal <eee.javed@xxxxxxxxx> wrote:
 

Thanks for your response. I found a document on Cool roof and it says:


"The most important feature of an ideal cool roof is that its surface strongly reflects sunlight. 
The surface of an ideal cool roof should also efficiently cool itself by emitting thermal radiation. 
Thus, a cool roof should have both high ?solar reflectance? (ability to reflect sunlight, measured 
on a scale of 0 to 1) and high ?thermal emittance? (ability to emit thermal radiation, also 
measured on a scale of 0 to 1). The solar reflectance and thermal emittance of a surface are 
called its ?radiative? properties because they describe its abilities to reflect solar radiation and 
emit thermal radiation".  

http://coolcolors.lbl.gov/assets/docs/fact-sheets/Cool-roof-Q%2BA.pdf

It means cool roof has both the properties i.e. Thermal reflectance and Solar Reflectance so according to this i need to consider both the values for cool Roof. Please guide me on this..

Regards!

On Thu, Oct 4, 2012 at 12:09 PM, Jeremiah Crossett <jcrossett@xxxxxxxxxxxxxxx> wrote:
 

I thought Solar Absorptance was the key input for SRI- 





Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions
120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951
  






On Thu, Oct 4, 2012 at 11:22 AM, Javed Iqbal <eee.javed@xxxxxxxxx> wrote:
 

Hi,


I'm trying to see effect of roof reflectivity on Energy consumption and as per I/O guide there are two parameters Thermal absorptance and Visible absorptance which accounts the impact of reflectivity. Can anybody guide me on which value needs to be considered for high SRI/Reflectivity study.

Thanks in Advance!

--


Javed Iqbal, LEED AP, CEA
Energy Analyst 






--


Javed Iqbal, LEED AP, CEA
Energy Analyst 





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