Re: [EnergyPlus_Support] simulating a coat of reflective paints (cool roofs)

["Asit Mishra asitkm76@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

That is where I am seeking advise. As per data from manufacturers and data from certain handbooks (an example I had attached in a previous email), the cool roof paints/coatings/tiles have a high value of emissivity (say 0.9) as well as high value for solar direct reflectance (say 0.8). So, how do I adjust the values of Thermal Absorptance, Solar Absorptance, Visible Absorptance to obtain similar nature?

Regards,

asit

On Thu, Jul 10, 2014 at 12:05 PM, 'jeannieboef@xxxxxxxxx' jeannieboef@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Solar radiation includes for all frequencies in the EMR-spectrum.
Thermal Absorbtance = Infrared (IR) spectrum (long-wave) which
overlaps very slightly with some of the visual spectrum.

When we talk about the emissivity of a product, we usually refer to
it's IR emissivity. This is because this bandwidth carries
proportionally the most energy (by far) of all the bandwidths (that
generally get absorbed by most materials) and accounts for a very
large percentage of all absorbed solar radiation.

So how can it be that you have specified 0.90 for Thermal Absorbtion
whilst visual and solar absorbtion are 0.2 (which I find
unrealistically low)?

Usually the Thermal Absorbtion is the most important field and is at
least similar to the Solar (because it has the heaviest energy
weighting).

Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)

i. A.
Jean Marais
b.i.g. bechtold
Tel. +49 30 6706662-23

On 10.07.2014, at 06:11, "Asit Mishra asitkm76@xxxxxxxxx

[EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

> 0.9, !- Thermal Absorptance
> 0.2, !- Solar Absorptance
> 0.2; !- Visible Absorptance

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Posted by: Asit Mishra <asitkm76@xxxxxxxxx>

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