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Louisanna Pacific makes a new product called TechSheild. It is 1/2 CDX with a foil backing. It is placed on the roof with foil down over the rafters as would normally be done on a roof installation. They claim it reflects 95% of the suns radiant heat. I called them to ask if a metal roof does the same thing. They could not answer. I am going to use a metal roof and do not want to invest the extra money in the TechSheild product if the metal roof does the same thing.
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I visited L-P's website and looked up this product. I did not find a lot of detailed information concerning its actual test performance. I am not disputing their claim of 97% reflectivity but I suspect that number was achieved in specific testing done according to specific standards and that it might be tough to achieve that dramatic of a number in the real world.
Different metal roofs achieve reflectivity in different ways. First, there is the outside coating on the product. Light colored and specially formulated dark colored coatings can be used to relfect away radiant heat.
Next, many residential metal roofs have airspaces between the roofing and the decking. That helps block heat transfer by conduction.
Also, many metal roofs have relatively shiny back sides which can further enhance reflectivity.
Oh, and there are some variations related to the base metal type -- galvalume, galvanized, aluminum, copper, etc.
I do not see any way to draw any direct correlations between the L-P product's reflectivity and metal roofing's reflectivity on a generic basis. And, again, I am uncertain whether L-P's numbers can be achieved in the real world.
There is soemthing to be said for achieving your reflectivity at the very top of the roof rather than in the decking where heat can be transferred to trusses, etc.
My real advice would be to use the special decking and a metal roof in conjunction with one another for ultimate efficiency. I do not think you'll ever regret that.
7/24/2002
Or copy this URL: https://www.metalroofing.com/spirit/comment/806/find/Isaiah Industries, Inc.
7/30/2002
Or copy this URL: https://www.metalroofing.com/spirit/comment/807/find/