I've said for years that we should have white roofs. There is really no reason to have an attic get 120 to 150F. Everyone is just used to the dark shingled roof. Some do the metal roofs, but they are more expensive in the short run. But, this idea is really creative. This guy named David found he could coat his roof with lime and water (whitewash) and it lasted for a few years. Who knows how long it would last, but at $14 for materials, you could coat the roof every few years and still save a ton of money.
Note that in the picture below that the roof could use a couple more coats. But, this was just a test and it proved to work very well, even though the roof wasn't completely white.
His results were fantastic; 8F to 10F cooler in the house and 30 to 40 degrees cooler in the attic. Now, imagine mixing this idea with the cheap air conditioning idea I talked about back in 2010.
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