This is a really cool article about the innovative ideas that are coming forth in the roofing industry. It looks like the idea still needs some tweaking. But, we may see more materials like this in the future!
By Jeff Salton
23:11 November 29, 2009 PST
Prototype roof tiles that turn white to reflect heat when they get hot seem like a pretty cool idea, as do tiles that turn black to absorb heat when it’s cold. That’s why a team of Massachusetts Institute of Technology (MIT) graduates has won the third annual MIT MADMEC (Making and Designing Materials Engineering Contest) by demonstrating their thermally-activated, color-changing, roofing material called “Thermeleon” (as in chameleon).
Using phase-change polymer gel-filled tiles, the team is able to control the light energy transmission properties of the roofing material, meaning that on a hot day the roofing material turns white to reflect heat, but on a cold day the material becomes transparent and absorbs heat back into the home.
Many modern homes with black roofing shingles absorb energy from the summer sun leading to higher cooling bills and wasting much of that solar energy. While this heat absorption factor may be offset in the winter with the home taking advantage of the sun’s energy reducing heating bills (often only slightly) the problem remains what to do about the intense summer sun that turns into interior heat.
White roofs are an obvious solution – but permanent white roofs, such as factory-painted materials, repel much of the advantage of winter heat absorption. While this solves the problem of summer heat it doesn’t provide any advantage in winter. Having a tile that automatically changes color depending on the temperature is a great solution all year round.
While the team says most of its testing has been conducted on a gel that transitions at around room temperature, it is able to select from a wide variety of transition temperatures ranging from approximately 0-100°C (32-212°F) and beyond.