What is Cellular Glass Insulation?

What is Cellular Glass?

Cellular glass insulation is a lightweight, low embodied carbon building material. Used as load-bearing structural fill, cellular glass is a high performance aggregate that can be used across the construction industry. Uses include: sub slab insulation, green roof fill, and civil infrastructure applications. In residential and commercial sub slab insulation, cellular glass insulation can replace rigid foam board, eliminating petro-chemicals from projects.

As lightweight fill, cellular glass can replace a substrate drainage media in green roof installations, reducing weight stress on building structures, and allowing for creative landscape architecture designs. In civil and infrastructure applications, cellular glass can act as an inert, non-leaching fill. Because cellular glass is so lightweight, it can easily be transported to sites, where it can take the place of crushed stone aggregates, while reducing the overall embodied carbon footprint of projects.

Cellular Glass Production

Cellular glass insulation gets its name as a nod to its production. To start, recycled glass cullet is ground into a powder and mixed with a foaming agent. That mixture is then fed into a belt furnace and kiln fired to 1650°F. At that temperature, the glass powder softens, causing the mixture to foam, creating a network of closed-cell micropores. Upon exiting the kiln, thermal stress causes the cellular glass sheet to crack into aggregate sized pieces, which are fed into a bunker for storage before being delivered to sites. For more information about cellular glass production: find the Glavel Foam Glass Guide.

Cellular Glass vs Foam Glass

Cellular glass insulation can also be referred to as foam glass gravel or foamed glass aggregate. They’re the same product that carry the properties of glass in the form of a high performance aggregate. It’s more commonly called cellular glass in Europe, where it’s been produced for nearly 30 years. American markets use the term foam glass gravel for residential applications and foamed glass aggregate for civil projects.

Example Installation

The image below shows an installation of cellular glass in a sub slab insulation application. Cellular glass can be employed as a replacement for both crushed stone and rigid foam board. With thermal insulation of R1.7 per inch, cellular glass is a 2 for 1 installation.