News Home & Design Glavel Could Replace Plastic Foam Below Grade By Lloyd Alter Lloyd Alter Facebook Twitter Design Editor University of Toronto Lloyd Alter is Design Editor for Treehugger and teaches Sustainable Design at Ryerson University in Toronto. Learn about our editorial process Updated May 22, 2019 06:39AM EDT ©. not a very exciting photo but an exciting product/ Glavel Foam Glass Gravel Share Twitter Pinterest Email News Environment Business & Policy Science Animals Home & Design Current Events Treehugger Voices News Archive Going foam-free is getting easier and more affordable. We often talk about how problematic plastic foam insulation is, being made from fossil fuels, foamed with greenhouse gases, and treated with flame retardants. But for use below grade, affordable alternatives are hard to find. Some, like Alex Wilson of BuildingGreen, have used foamed glass slabs, but they are expensive. Meanwhile, recyclers are buried in glass. Some is recycled into glass, some is made into fiberglass, some goes into concrete and road beds. But according to the Glass Packaging Institute, only 33 percent of glass is recycled. Often it is collected, ground up into cullet and dumped into landfill. © Glass to Glavel That's why a new product available in North America, Glavel, is so interesting. CEO Rob Conboy explained to Green Building Advisor: "We love the fact that we’re going to be taking something of little or no value and turning it into a product that’s good for the planet and an amazing alternative to a petroleum-based product that’s laden with lots of chemicals, and do some good." Glavel explains how it is made: To produce GLAVEL, processed recycled glass shards are ground into a powder and mixed with a foaming agent. This mixture is deposited on a mesh that slowly passes through a furnace. The powdered glass is heated to a temperature of 1650°F, which causes the glass powder to foam into a mass of 9.4 lbs./cf – 150kg/m3. It then cools and hardens into foam glass. The final product has a closed cell structure and has a compressive strength above 40PSI. As the foam glass tumbles off the conveyor it breaks up into smaller pieces and the result is foam glass gravel. © Glavel under slab detail Builders today put gravel for drainage and foam slabs for insulation under concrete slabs, and in Passivhaus designs, you need a lot of insulation. Glavel can do both jobs at once. Conboy says it is cost-competitive and might even be cheaper. It is totally inert and non-combustible, just like glass. TreeHugger regular Ken Levenson likes it too, and when he is not under arrest for supporting climate action, he sells it through 475 High Performance Building Supply, telling Green Building Advisor: "You’re taking recycled glass and upcycling it into an insulation product for buildings. It’s one of the few products that has this magical, virtuous cycle — how we can build and not just minimize our impact but have a positive impact." Rob Conboy tells TreeHugger that Glavel is currently imported from Europe by the container load while he tries to get a foothold in the insulation market, but the intent is to build a facility in North America soon. The stuff does have a carbon footprint because the kilns are fired by natural gas, but according to Greenspec, it is still way lower than polyurethane or XPS, the blue stuff that is so common in foundations. This is very exciting; building plastic-foam free is getting easier and more affordable every day. Maybe next they will start making Foamglass boards too, and we can wrap our homes in recycled bottles. More at Glavel.