It sounds like something from Back to the Future: A roof that can change between absorbing heat from the sun and reflecting it. It is well known that lighter colors reflect heat and help keep things cooler while darker colors absorb heat. So how about a roof that can do both?
There is a material – made from used cooking oil of all things – that is smart enough to change between reflecting and absorbing heat when a thermometer tells it to. “This is one of the most innovative and practical roofing coating materials developed to date,” said Ben Wen, leader of the research project and vice-president of United Environment & Energy, “In addition, it will provide a new use for millions of gallons of waste oil after it is used to cook french fries and chicken nuggets.”
You can read more about the material and its “weather tuning” properties here: http://www.tgdaily.com/sustainability-features/49009-smart-roof-could-slash-energy-costs#GGdzwfdM2fPsyOwf.99
In the article, written in 2010, it says the roof material could be ready for commercial use in three years so keep your eye out. This could be a great way to help ease the heating and cooling burden on your furnace and air conditioner and save you money on your energy bills.