Most homeowners looking to lower heating or cooling costs know the drill. First thing to do is ensure the house is properly insulated, typically by rolling down a layer of the pink fiberglass stuff or having a fluffy version blown into their home’s walls.
But here’s a relatively new idea: Instead of adding insulation, build the structure from bricks already stuffed with a material known for its thermal conductivity. The bricks do-away with extra layers of insulation and decrease the thickness of a wall.
The building industry has begun to incorporate internal-insulation walls using insulated bricks and panel systems that use materials like perlite, mineral wool, or polystyrene as insulators.
Now, scientists at Swiss research group Empa claim they’ve created the best insulating brick of the bunch. It uses a different insulating material than the rest: aerogel, says Jannis Wernery, who led the project. He’s a scientist in Empa’s Building Energy Materials and Components department, part of The Swiss Federal Laboratories for Materials Science and Technology.
A wall constructed from the aerobricks conducts heat up to eight times better than one made from standard clay and shale bricks, Wernery’s group has shown.
The bricks offer strong insulating and building benefits. For example, a regular brick wall would need to have a depth of more than 6 feet to provide the same insulating properties as an 8-inch deep aerobrick wall. A wall made from perlite bricks would need to be about 35 percent thicker than an aerobrick wall to have the same insulating properties, Wernery says.
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In order to achieve the same insulation values as a 165 mm thick wall of aerobricks (left), a wall of perlite bricks (middle) must be 263 mm thick, and a wall of non-insulating bricks, right, must be more than one-meter thick. Credit: Empa
Aerogel is a lightweight, manufactured material made from a gel in which gas replaces the gel’s otherwise liquid component. The tiny bubbles minimize the movement of the air molecules through the material, making it an ideal thermal insulation material, Wernery says.
Empa researchers have already used aerogel in an insulating plaster that, among other things, allows historical buildings to be retrofit for minimal energy loss without affecting their appearance.
They then turned to insulating bricks with aerogel. Like similar bricks on the market, aerobricks are made from hollowed standard clay stuffed with aerogel.
“The aerogel can easily be filled into the cavities and then it joins with the clay of the bricks,” Wernery says. “The aerogel stays in the bricks and you can work with them as usual.”
Because aerogel is expensive, Empa researcher Matthias Koebel and his team have developed a new production method they hope will bring down the costs of aerobrick production.
The aerobricks have a measured thermal conductivity of 59 watts-per-meter Kelvin. Currently available insulating bricks made with air, mineral wool, or perlite have thermal conductivity of 70 to 90 mW/(m·K), according to Empa.
Thermal conductivity measures the ease with which heat can travel through a material by conduction, the main form of heat transfer through insulation. The lower the figure, the better the insulation.
The researchers used a thermal-conductivity measuring device to find these results.
In Part 2, we look at some of the aerobrick’s additional features and cost comparisons.
Jean Thilmany is an independent writer.