The standard sub slab insulation installation of North America involves some combination of rigid foam board (EPS, XPS,etc.) and crushed stone aggregate. This sub base combination of materials serves to insulate under slab while providing a drainage layer to keep moisture and water away from a building’s foundation. While the thermal insulation per inch of rigid foam board may be high, it comes at an even higher environmental cost. Derived from petroleum, EPS and XPS have high embodied carbon to start, not to mention they require chemical agents to remain fire resistant. Crushed stone aggregates are also incredibly heavy and bulky, making transportation arduous at best. There must be a better way to do foam free sub slab insulation.

The built environment is responsible for nearly 40% of greenhouse gas emissions, 28% of which comes from the embodied carbon; that means 11% of greenhouse gas emissions are embodied carbon.

Foam glass gravel, also known as cellular glass insulation has the power to reduce the embodied carbon by eliminating both foam board and gravel from the sub slab insulation equation. Used in Europe for over twenty years, foam glass gravel is manufactured from recycled glass, requires no virgin materials, and no petroleum to manufacture. Foam glass gravel is thermally insulating and boasts high compressive strength so it is capable of replacing both the backfill gravel and rigid foam board used as sub slab insulators. This not only reduces the installation efforts needed to set up sub slab insulation, but it also simplifies purchasing and supply chain site logistics for a foam free sub slab installation. While a skilled professional is required for the cutting and installation of rigid foam board, foam glass gravel’s installation is a far simpler process that involves only a plate compactor once Glavel is in the foundation. 

foam free sub slab insulation

To compare the embodied energy by taking megajoules of energy required to produce a kilogram of product, EPS sits at 88, polyurethane foam has 101, while foam glass sits at 20. Also bear in mind that these calculations are done with manufacturing of foam glass powered by fossil fuels. Glavel’s foam glass gravel plant will be powered by renewable energy, which will stand to further reduce the embodied energy and carbon used in production, eliminating 1900 tons of carbon emissions annually. 

Given that foam glass gravel doesn’t sacrifice building performance or longevity, it should quickly become the new market standard for foam free sub slab insulation. Building with Glavel will not only save time and money, it’ll help the planet too.