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-   -   Painted white roof drops house temps 8-10 degrees (https://ecorenovator.org/forum/showthread.php?t=1060)

virginiajim 07-07-11 04:22 PM

Sources of roof paint
 
A few years ago I looked into roof paint that incorporates ceramic reflective beads which could be applied to asphalt shingles from a company called Hy-Tech Insulating Roof Paint. I never could find information about an actual case of such an application, or what it looked like. The paint is expensive and you would prefer to have an attractive result. Has anyone experience with thermal reflective paint? Has the discussion here so far only involved white latex paint?

Jim in Smithfield, VA

tomboy mom 07-07-11 09:56 PM

Quote:

Originally Posted by Daox (Post 14400)
Painting the roof would still be a good idea and would help. It will still get hot and the radiant barrier will still help once the roof has heated up.

if only the hoa would feel the same way :rolleyes:.

rhino 660 07-10-11 01:57 PM

yea i thing my Nazi hoa will gas me for painting my roof white... maybe ill do it just to be a rebel, ive been contemplating it for about 2 years now lol.

rhino 660 03-15-12 10:37 PM

well im preparing to go to my HOA and ask for premission to paint my roof white

Plantman 03-20-12 09:14 PM

So if heating load is greater than cooling load, it would be advantageous to have a dark roof that heats up in winter than a light roof that reflects heat in summer? What about greenhouse paint that is white but designed to last only through the warm part of the growing season and is mostly washed off by rain by the following winter when the sun is needed to heat the greenhouse?
Quote:

Originally Posted by S-F (Post 12973)
Sounds great but in mixed temperature climates it's probably not such a good idea. I can live with a hot house easier than a cold house. I can survive 90 degrees inside but 0 degrees would be difficult.


MN Renovator 03-20-12 11:36 PM

Quote:

Originally Posted by Plantman (Post 20812)
So if heating load is greater than cooling load, it would be advantageous to have a dark roof that heats up in winter than a light roof that reflects heat in summer? What about greenhouse paint that is white but designed to last only through the warm part of the growing season and is mostly washed off by rain by the following winter when the sun is needed to heat the greenhouse?

It doesn't work that way because your roof needs to stay cold in the winter or you'll have ice dams. This is one reason why there are issues if attics aren't either ventilated or directly insulated. I've been in my attic when its 30 degrees outside with no clouds and the sun up for hours when it wasn't covered in snow, you still need a coat. Don't forget once the black roof is covered in white snow, it doesn't matter what color your roof is anymore and there is less sun in the winter too which is why it is a much bigger deal in the summer.

Plantman 03-21-12 07:48 PM

What if you have a cathedral ceiling with no attic?

MN Renovator 03-21-12 08:01 PM

"or directly insulated." The roof has insulation directly against it(between the roof decking and ceiling) which will be similar. In a situation where there is a large cavity such as a flat ceiling and a sloped roof, that extra space needs to be vented unless the roof itself has insulation directly against it. In a case where there is a flat ceiling and an open cavity with insulation against the roof(called a 'hot roof'), the entire cavity is considered conditioned space since normally you wouldn't put insulation against both the roof and between the ceiling and the living space, its one or the other, otherwise issues with moisture become a real problem unless that space is vented and if its vented you wasted some money on insulated both sections. ..unless the 'insulation' against the roof is a reflective heat barrier but I don't consider those insulation like some people say they are. I like to use insulation as a term used for a barrier to conductive heat transfer, hopefully in conjunction with a proper convective heat barrier as part of the system.

S-F 03-22-12 04:13 PM

Yeah I agree that this should be only academic. If you have a vented roof I think there should be R-60 up there and then it doesn't matter what color your roof is.... unless you need to go up in the attic in the summer. In the summers here i New England where everyone has back shingles I am SUFFERING. Sure the home owners talk about how cool the house is after R-60 is in place but putting it there is miserable. Nothing like blowing cellulose in a cramped space in 130 degree heat. Even if you use good cellulose that isn't too dusty, like the Home Depot stuff, you still walk away completely covered is grey glue. When I put a metal roof on my house it's not going to be black! Also on the menu for this weekend is to install three lights in the attic with a switch So I can see what I'm doing when I air seal it to the hit in the summer. Beats the hell outta carrying a drop light around.

Xringer 03-22-12 06:46 PM

It's almost 8PM and my attic is still 91 deg F.
Musta been cooking up there this afternoon!


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