Product Review

A New Foam-Free Sub-Slab Insulation

Foam glass aggregate made from post-consumer recycled glass bottles can replace both foam insulation and aggregate below grade.

Extruded polystyrene’s (XPS) high R-value and water resistance have made it the default insulation for below-grade applications, but its petroleum-based styrene chemistry, inherent flammability, and high-global-warming-potential (GWP) blowing agents make these board products less than desirable environmental choices. And although high-density expanded polystyrene (EPS) uses a low-GWP blowing agent, it shares similar styrene and flammability concerns.

A more environmentally sound insulation material, cellular glass, is made from glass with no blowing agents, flame retardants, or petrochemicals. Cellular glass board products such as Foamglas, a 2010 BuildingGreen Top 10 product (now owned by Owens Corning), are expensive and tricky to install, but AeroAggregates and Glavel are now offering foam glass aggregates (FGA) with similar performance attributes to cellular glass board, but in an easy-to-install form that can take the place of both insulation and aggregate.

Published April 2, 2019