A Vermont company is nearing the start of production of a building material made from recycled glass that can be used as both a drainage layer and sub-slab insulation.
Burlington-based Glavel announced it would open its new, 25,000-sq.-ft. production plant in nearby Essex and be ready to ship product by January.
On the production line, pulverized glass combined with glycerin, used as a foaming agent, travels on a conveyor through an oven at 1400°F–1600°F. The result is chunks of a gray, lightweight material weighing between 330 and 375 lb. per cubic yard, according to specs provided by the company.
Glavel will become one of two U.S. producers of a material that got its start in Europe. AeroAggregates also makes a foamed-glass product in Eddystone, Pa. Until now, Glavel has imported foamed glass from its German affiliate Glapor. That’s still the case, but CEO Rob Conboy says increases in container shipping charges have virtually priced European foamed glass out of the market.
In residential construction, foam glass can act as a drainage layer, a capillary break, and as thermal insulation below a concrete slab. It would replace rigid polystyrene foam insulation (XPS or EPS) as well as crushed stone that’s typically used for that purpose. When mechanically compacted, foamed glass has an R-value of about 1.7 per inch, according to the company.
AeroAggregates CEO Archie Filshill told GBA in 2019 that foamed glass is up to 90% lighter than stone aggregate, significantly reducing transportation costs. It can be used as a free-draining backfill around foundations and retaining walls and underneath patios, he said.
Conboy has previously said that foamed glass would be attractive to builders who are trying to steer clear of rigid foam because of environmental concerns, including the use of foaming agents with a high global warming potential.
New York–based 475 High Performance Building Supply lists Glavel on its website but the company says inquiries and orders are sent directly to Glavel. The retailer describes Glavel as a “load-bearing, thermal-insulating substrate” that can replace the aggregate layer under a concrete slab.
Conboy said by telephone that Glavel is working with logistics partners to make the product available anywhere in North America. Some, like 475, would be “lead generators” without actually stockpiling Glavel. But the company also is working on setting up a network of distributors around the country where builders could get Glavel on shorter notice. In New England, builders will be able to order directly from Glavel in Burlington.
A list of distributors would be ready by the first quarter of next year, Conboy said.
Glavel will be available in 2-1/2-cubic-yard bags and sell for $65 per cubic yard (not including freight charges). The bags are 6-ft. tall by 4-ft. square, so they will fit on a pallet for shipping.
Glavel is intended to replace both the insulation and crushed stone and gravel beneath a concrete slab, and when the cost of the rigid insulation (either XPS or EPS) plus the crushed stone is taken into consideration, Glavel should prove to be 10% to 15% less expensive within 300 miles of the Vermont plant, Conboy said.
The company says it will use between 15,000 and 18,000 tons of recycled glass per year, gathered in a 100- or 150-mi. radius of the Vermont plant. The output will be some 150,000 cubic yards of Glavel per year, Conboy said.
Electricity to run the production line, sourced from Green Mountain Power, will be “virtually carbon-free,” Conboy said, with the company aiming for 100% renewable power in the future.
Conboy said that AeroAggregates is the only other manufacturer of foamed glass in the country, but that he suspects interest will grown and other producers are likely in the future.
Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.