Vigneshkumar,
I would interpet this as such:
Your base reflectance should be .30 and your modeled reflectance should be .45 for the life of the roof.
It looks like this prevents you from using a modeled reflectance of .70 because the .70 will degrade over time and won't truly be representative.
Lori Jore, PE
Pro-Tec Energy
www.Pro-TecEnergy.com
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, vignesh kumar <vigneshkumar1986@...> wrote:
>
> *Hi Could any one clarify this :*
> **
> **
> *"By default, exterior roof surfaces, other than those with ventilated
> attics, must be modeled assuming a surface reflectance **value of 0.30.
> When a proposed design calls for a reflective roof surface, however, the
> model may assume a long-term **average reflectance of 0.45, which credits
> the lower heat absorption of the reflective surface and makes a conservative
> **allowance for degradation of the reflectivity over its lifetime. In order
> to qualify for this credit, the reflectance of **the proposed design roof
> must exceed 0.70, and its emittance must exceed 0.75. "*
> **
> *So does this mean , if my proposed case roof has a higher roof
> reflectivity than 0.70 and higher emmitance than 0.75 ,means ** my base
> case roof reflectivity should be 0.45 , if it is the case then my there will
> be reduction in my savings of the proposed case with the base case , then
> how will this becomes a credit *
> **
> *Thanks and Regards*
> vigneshkumar
>
--
vigneshkumar
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