Quote:
Originally Posted by Plantman
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?
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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.