ÂSorry- Â missed a word...ÂHere is a quick illustrationÂ0.9, Â Â !- Thermal Absorptance = 0.9 Thermal Emissivity0.92, Â !- Solar Absorptance = 0.08 Solar Reflectivity Â
â??â??Jeremiah D. Crossett  | Senior Analyst  | LEED Green Associate Â
On Mon, Jul 7, 2014 at 8:34 AM, Jeremiah Crossett jcrossett@xxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
ÂHere is a quick illustrationÂ0.9,      !- Thermal Absorptance = 0.9 Emissivity  0.92,        !- Solar Absorptance = 0.02  0.92;        !- Visible Absorptance  = 0.02
â??â??Jeremiah D. Crossett  | Senior Analyst  | LEED Green Associate Â
On Mon, Jul 7, 2014 at 5:46 AM, Asit Mishra asitkm76@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
ÂDear Jeremiah,             I am very thankful for the two spreadsheets. They will be very useful in my work.ÂI was in particular referring to the paints that have been called cool roof paints.These are a few values for solar direct reflectance as quoted from a database provided by US-India Joint Center for building Energy Research and Development. (I am attaching the original document as well)Thermatek Heat Reflective Paint:  0.8973Cool paint AK-103, Aroma paints: 0.7324Sun cool - LHP coating: 0.9097Actually, when I started out, I did what Jean had mentioned - change the reflectivity/solar absorptance etc. of the outermost layer for a wall or roof. The introduction of a thin filmÂwas just for convenience so that I could make it an outermost layer in any kind of wall without having to change properties of standard layers.ÂEither way, results still did not show much change in the year round indoor temperatures, i.e. before and after use of the reflective coats.ÂRegarding emmisivity, I wanted to know exactly which property to control to change emissivity.The typical cool roof paints have a high reflectivity and a high emissivity as well.ÂLooking at a typical material specification, I am unable to see how I change this for a surface/the outermost layer.example Material,  A1 - 1 IN STUCCO,     !- Name  Smooth,          !- Roughness  2.5389841E-02,      !- Thickness {m}  0.6918309,        !- Conductivity {W/m-K}  1858.142,         !- Density {kg/m3}  836.8000,         !- Specific Heat {J/kg-K}  0.9000000,        !- Thermal Absorptance  0.9200000,        !- Solar Absorptance  0.9200000;        !- Visible AbsorptanceI am sorry if my question is not making full sense. And thank you both for your immediate response and help.Regards,
asitOn Mon, Jul 7, 2014 at 9:46 AM, Jeremiah Crossett jcrossett@xxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
ÂI  my experience unfinished metal is the only thing that warrants using anything far off from default, and only modify absorbence for parametric studies.  Attached is a spreadsheet you can find online that can be used to fit product data into E+, just remember that solar [and visible] absorbence is the inverse of the reflectance info you can get from manufactures.  Also attached is a spreadsheet where  absorbence / reflectance = albedo..Hope this helpsÂâ??â??Jeremiah D. Crossett  | Senior Analyst  | LEED Green Associate Â
On Sun, Jul 6, 2014 at 6:59 PM, Asit Mishra asitkm76@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
ÂasitRegards,Please adviseSecondly, normally what I have seen in material specifications, while values for absorptivity can be specified, there was no obvious way to specify a high emissivity (apart from indirectly doing so using surface roughness).This did not seem to produce desired resultsHello,        I would like to have some idea on how you all might have approached simulating the effect of a reflective coat of paint. The way I went about it is defined a material with low absorptivity and added a thin layer (0.5 mm) to the roof/wall construct.
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Posted by: Asit Mishra <asitkm76@xxxxxxxxx>
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