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I’m planning to install painted galvanized roofing on a house I’m currently building and am looking for an alternative to using 30lb. felt under the roofing. My thinking is that placing a layer of black asphalt impregnated paper under the roofing will act as a huge radiator in the winter and a heat sink in the summer. I read somewhere that Tyvek housewrap can be used, but it’s very slippery, which is why Dupont doesn’t recommend it for this purpose. I’ve also heard of using buiders aluminum foil on paper backing. Anyone have any experience with either of these or any comments in general.
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In my area, 30 lb felt is not recomended and rarely used for standing seam metal roofs. Instead, a product called "Peel and Stick" or "Fire and Ice" is used. This is a rubberized membrane, with an adhesive on the back side. One peels a paper liner off the product, and sticks it directly to the plywood underlayment. Any nail holes will self seal. It is equivalent to 60 lbs of felt, I have been told.
Standing seams can leak slightly, so extra waterproofing is necessary. Additionally because of their long life (50 years plus), a longer lasting waterproofing is desired.
I detest Tvek as a product line, and its worst qualities would be amphlified on a roof. It is slippery, not particularly waterproof, the nail holes do not even come close to self sealing, and because of the width of the roles, would be a bear to install. The one thing it is good for is as an exterior vapor barrier, something you wouldn't need on a roof.
I would stick to tried and true product lines on your roof. They have been around longer than you, and will be there for you after you are gone, and your roof is still there. My recomendation: 60 lbs of felt or the Fire and Ice product. Good Luck!
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You are concerned about balck tar paper radiating beneith your roof- but the tar paper is not exposed so it does not matter if it is black, white or any other color. use "snow and ice" where you may have ice dam problems and tar paper the rest. I doubt a creative use of an untested product would be a good idea. I would stick with tried and tested. Should you still be concerned with roof temperature, make certain you have proper ventilation and perhaps use a lighter color for your roof.
m.schultz
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I'm planning to install painted galvanized roofing on a house I'm currently building and am looking for an alternative to using 30lb. felt under the roofing. My thinking is that placing a layer of black asphalt impregnated paper under the roofing will act as a huge radiator in the winter and a heat sink in the summer. I read somewhere that Tyvek housewrap can be used, but it's very slippery, which is why Dupont doesn't recommend it for this purpose. I've also heard of using buiders aluminum foil on paper backing. Anyone have any experience with either of these or any comments in general.