A Recycled, Green Option from a Green Manufacturer
By Evan Lawrence
Builders looking for an exterior finish material with the appearance of wood but which stands up better to weather and insects have a new choice, Boral Tru-Exterior siding and trim.
It looks like wood and feels like wood, but it doesn’t act like it,” said Boral product manager Aaron Sims.
Six years in development, Tru-Exterior siding consists of a proprietary polymer blend encapsulating highly refined fly ash, a by-product of coal combustion that would otherwise go to a landfill. Fly ash is endorsed by the U.S. Green Building Council and the U.S. Environmental Protection Administration for use in construction materials. The siding has a minimum of 70% recycled content, as certified by SCS Global Services and is Cradle to Cradle certified.
Through the burning process, the ash becomes very spherical,” Sims said. “It has unique properties.” Although fly ash contains some toxins found naturally in coal, the polymer keeps them from leaching, Sims said. To ensure the safety of its employees and customers, Boral tested the siding for toxins and found that they were below detectable levels.
The siding comes in 16-foot lengths in seven styles. It accepts most fasteners and doesn’t need adhesives or sealants. It carries a 20-year limited warranty.
The product “is especially good for homeowners,” Sims said. “It doesn’t rot or decay.” Wood can swell, shrink, warp, or crack in response to changing temperature and moisture. In contrast, Tru-Exterior siding “is very stable, and insects don’t eat it. Animals may try it, but they usually give up. It has incredible termite resistance.” It’s also fire-resistant, with an ASTM E84 score of below 35. “That’s very low,” Sims said.
Unlike vinyl and some composites, the material can be painted any color with exterior latex paint. “We’re mostly focused on the residential market,” Sims said. “The siding products are high-end premium. We sell to a lot of historic districts on the East Coast.”
Boral manufactures Tru-Exterior products in a LEED silver-certified factory in East Spencer, N.C. The company purchases renewable energy credits, powers its facilities with alternative energy sources, and has its own waste water management systems. It belongs to the U.S. Green Building Council and was a founder of the Climate Registry.
Locally, Boral products are available at Oakes Bros., Inc. in Bradford, Vt. One local project that is using the product is for a vacation home on Lake Sunapee in New Hampshire.
The house is on the lake and had some pretty extreme decay,” said Dale Oakes, a manager at the store. “The owner wanted something that would stand up better.” They are also using cedar shingles, “which have natural decay resistance,” Oakes said.
Tru-Exterior siding “costs less than cedar and some other products, and more than vinyl siding,” Oakes said. However, vinyl most commonly comes in light and pastel colors and to paint it generally requires paints formulated specifically for plastics. “This siding can accept dark colors,” he said. “It really looks like wood when it’s finished. I used it on my own house.”
Oakes had one warning: Builders should use carbide tools and not regular tool steel. The gritty fly ash “chews tool steel right up,” he said.
Evan Lawrence is a free-lance writer in Cambridge, NY, specializing in sustainability, environmental, and health topics.