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I live in the Southern California desert and am doing some renovations to my house. Our AC line runs on the roof from the center of the house 25' to the west side and down the wall to where the exterior unit sits. The insulation on the line is badly deteriorated black foam that has been painted white in some areas and has reflective silver foil tape on others. Which "finish" (plain black foam, white flexible paint, or reflective foil tape) is best where 110-115 degree days are common?

Thanks!

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Gloss white paint reflects most heat. a clean slick surface that does not hold dirt is best. Silver/aluminum reflects more BUT white re-emits most of the radiation it absorbs and silver does not . Acrylic white is not so good;great resistance to UV but it chalks more so the surface becomes dull/dirty. I read this 40 yr ago in research for oil storage tankage, no hope of finding the reference. But when I see painted oil tanks today ,they are white so apparently the physics has not changed.

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  • Pretty much what I thought, but thought it weird that three different people had left three different finishes on my roof. The white paint is elastometric roofing paint, so presumably well adapted to UV, I'll probably stick with it. Thanks!
    – MikeL
    May 26, 2020 at 3:39

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