material specification

Jutta Berns

onwer and principal

ecocentric (pty) ltd.

LEEDuser Basic Member

84 thumbs up

August 31, 2010

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Jacob Arlein

Director of Energy Services

Environmental Building Strategies

LEEDuser Basic Member

38 thumbs up

Tue, 08/31/2010 - 15:54

Jutta, I am not exactly sure what you mean by heat reflectance, do you mean thermal reflectance? Either way, heat reflectance is not the same as solar reflectance or albedo. Albedo is the ratio of total-reflected to incident electromagnetic radiation from the sun. This is a measure over all wavelengths of light. It is likely that this product is still a cool roof product with such a high thermal emmitance level, but you will have to determine the solar reflectance of the material to be able to accurately calculate SRI.

Jutta Berns

onwer and principal

ecocentric (pty) ltd.

LEEDuser Basic Member

84 thumbs up

Tue, 08/31/2010 - 16:27

many thanks for the response and i understand the point you make. unfortunately the data sheet simply states "heat reflectance" and "emittance" - as above - and also has a value for thermal conductivity (0.09 W/m°K). are there any other resources we could consult to help us calculate the SRI correctly with the information that we have available? indeed all products that we have been able to source so far (we are located in South Africa) only provide, if at all, values for heat reflectance and emittance. we are being pushed to make a decision on the coating and really do not want to lose the point on documentation, if it seems that we may be quite close! many thanks!

Tristan Roberts

Representative

Vermont House of Representatives

LEEDuser Expert

7780 thumbs up

Tue, 08/31/2010 - 16:45

Can you ask the manufacturer to clarify, or offer better data?This may simply be a language issue, where what they are calling "heat reflectance" is in fact "solar reflectance."

Jutta Berns

onwer and principal

ecocentric (pty) ltd.

LEEDuser Basic Member

84 thumbs up

Wed, 09/01/2010 - 14:08

Many thanks! have done so and it was indeed simply a language issue and the test reports have now confirmed the values. Such is the excitement of working on projects outside the US!