'Smart roof' coating made of old takeaway fryer oil

Eco-friendly boffinry entrepreneurs have proposed a radical new scheme to reduce energy consumption in the home. Rooftops should, they say, be coated with a revolutionary "smart roof" temperature-sensitive material made out of used cooking oil.

"This bio-based intelligent roof coating, compared with a traditional cool roof, could reduce both heating and cooling costs as it responds to the external environment," enthuses Ben Wen, lead inventor of the chipfat-based roofing tiles.

"It will help save fuel and electricity and reduce emissions of volatile organic compounds from petroleum-based roofing products. 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," he adds.

The idea is that you want your roof to reflect heat away in the summer, so keeping your home cool and avoiding the need for air conditioning. But in winter you want the roof to absorb sunlight and turn it into heat, saving on winter energy bills.

Short of painting your house black when it's cold and white when it's hot, this is difficult to manage. But Wen says his waste-based product can be "tuned" in manufacture to change from reflector to absorber at temperatures suited to where it is to be used.

Wen and his colleagues present their research at a chemists' conference in San Francisco this week. According to a statement issued by the conference organisers:

In producing the coating, waste cooking oil is processed into a liquid polymer that hardens into a plastic after application. Unlike raw waste oil, which can smell like French fries or fish, the resulting polymer is virtually odorless. Manufacturers could potentially produce it in any shade, ranging from clear to black, depending on what additives are used, he said. The material is also non-flammable and nontoxic.

Don't try getting up on your roof with a drum of old chipfat cadged from the local rapid noshery, though. Wen says such a plan won't work without his secret ingredients - and, quite apart from the resulting stench, it also "could well pose a fire hazard". Not to mention the risk of explosion: we reported two summers ago on the sobering case of an Oxfordshire man who blew up his garage, suffering severe burns in the process, while making biodiesel out of used oil sourced from his local Chinese takeaway*.

The fryer-refuse roof coatings could be in use in three years, reckons Wen.

It's to be hoped that supplies of old chipfat hold out: plainly it's our ecological duty to eat more fast food. ®

*Admittedly in that case it seemed likely that the explosion actually resulted from a buildup of alcohol fumes. Treatment with alcohol is recommended before using cooking oil in a diesel engine - though in a well-ventilated space.