October 16, 2009

Construction Corner | Korky Koroluk

Massachusetts Institute of Technology sees energy savings in black and white

Back in 1970, American sociologist and futurologist Alvin Toffler wrote a book called Future Shock. Its thesis was both simple and profound: Not only was the world changing, it was changing at an accelerating rate.

Toffler’s own short definition of future shock was “too much change in too short a period of time.”

Every year since the book appeared, the truth of its argument has been evident. Change is piled upon change year by year, month by month, week by week.

Back then, construction materials were pretty much the same as they had been 10 or 20 or 30 years before. Now, there is a whole new thing called materials science, and it deals with not only construction materials, but with materials of all kinds.

Many of them involve the use of the even newer group of scientific disciplines that we call nanoscience — the science of the super-small.

Scarcely a week goes by now without three or four articles about nanotechnology in building materials appearing on my computer screen.

One of the most recent involves promising a new idea being developed by a group of students. It isn’t ready for the market yet, but watch for it.

Students at the Massachusetts Institute of Technology have come up with roofing tiles that turn from black to white and back again as temperatures vary.

On hot days, when you want heat reflected away from your house, they would be white. Then, as temperatures drop and you want some of the sun’s heat absorbed by your house, the tiles turn black.

The idea of reflective white roofs has been around for a while, but the notion was given momentum when Steven Chu, the American secretary of energy, advocated white roofs in a speech soon after his appointment. Since he is a Nobel-prize-winning physicist, Chu’s comments carry a lot of weight.

He would like to see a wholesale change-over to white roofs. He acknowledges that, especially in northern cities, the summer’s gains in energy conservation could be lost in the winter, so the ideal would be to get the advantage of both white and black roofs.

The team of students took Chu’s statements and ran with them. They originally tried to develop a colour-shifting tile using mixed fluids, one dark and one light, whose density would change with temperature. The dark fluid would float to the top when it was cold; the white would float when it was hot. A good idea, but too complicated in application.

So they hit upon the idea of using a common commercial polymer in a water solution. The mixture is encapsulated between flexible plastic layers, with a dark backing.

At temperatures below a certain level (which can be chosen by varying the formulation) the polymer remains dissolved and the black backing shows through, absorbing the sun’s heat. But as the temperature rises, the polymer condenses into minute droplets that scatter light and so produce a white surface, reflecting the sun’s heat.

Now the students are working on an even simpler version in which the polymer solution would be contained in microcapsules which would be added to a clear paint that could be brushed or sprayed onto any existing surface. That would make the process quicker and cheaper.

They say that because the materials they use are common and inexpensive, the tiles could be manufactured at a price comparable to conventional roofing materials.

As world population climbs, world energy demand will intensify, and many solutions will have to employed.

There is no single “silver bullet” that will solve all problems.

So making more and more imaginative use of the sunlight that falls on our buildings could increase our energy supply while, at the same time, making our buildings more sustainable.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com

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