Rethinking Sub-Slab Insulation

It’s likely that your home is perched atop a combination of gravel, rigid foam board, and a moisture barrier; all of which sits directly below a concrete slab. This combination can insulate a home, but comes at a high environmental cost. The embodied carbon of this build is incredibly high due to the derivation of rigid foam board from petroleum, and the costs associated with transporting gravel, whose weight creates bulky delivery needs. 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. There must be a better way.

Foam glass gravel, also known as cellular glass 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 higher compressive strength than gravel 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. 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. 

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 sub-slab insulation. Building with Glavel will not only save time and money, it’ll help the planet too.

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