Do Glass Tile Thermal Solar Roofs Make Sense?

soltech glass roof tile photo

Preston at Jetson Green and Frida at Inhabitat discuss these lovely looking glass roofing tiles from SolTech Energy in Sweden. It is a solar thermal system, that transfers heat from the air to water that can be used for heating. Frida describes it at Inhabitat:

soltech glass roof system image

For starters, the tiles are made from ordinary glass and have about the same weight as those made of clay. Secondly, the system doesn't, like competitors' versions, heat up water or vacuum pipes, but clean air. The tiles are installed on top of a black nylon canvas, under which air slots are mounted. The black colour absorbs heat from the sun and the air starts to circulate. The hot air is then used to heat up water, which is connected to the house's heating system via an accumulator.

Solar thermal is the low-hanging fruit, much more cost effective than solar photovoltaic. See Solar Hot Water First. Then Photovoltaics.) This system looks quite lovely, but in Sweden and Germany, people build for generations and are used to paying a lot for roofs. In North America, everything is compared to asphalt shingles, which are cheap as dirt and almost universally used.

greenward roof vent

Last year at Greenbuild I saw an American system that did much the same thing, based on asphalt shingle roofs. It used a much simpler system based on the fact that roofs get hot and heat rises. I wrote:

This is one of those crazy clever ideas, replacing a four thousand dollar solar collector that people don't like putting on their roofs with a completely invisible one, taking wasted energy that we actually design our roofs to get rid of and putting it to good use. There is a bit of technology in the basement that is common to all solar hot water systems, but the basic collector is as simple and clever as you can get.

greenbuild greenward vent photo

According to Bob Vila, asphalt shingles cost $50 to $150 per square (100 square feet). Clay tiles can $ 500 per square. I suspect the glass tiles cost more than the fairly common (in Europe) clay. The tiles were designed in a traditional form because, as their head of business development says in Core77,

We chose a traditional shape of the tile initially in order to get easier and faster acceptance for the concept in a market (construction) known for it's conservatism and reluctance to test new ideas. With the traditional shape, we can merge our tiles with ordinary tiles, according to the clients wishes and demands.

But if you are not into a traditional clay tile roof, it seems to be an awfully expensive way to get heat out of your roof. There are many effective flat plate collectors or evacuated tube collectors that would do a far better job at a far lower cost. And if you don't want to have a collector on your roof, there is always the Greenward system, that is doing exactly the same thing.

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