Definitive Foam Glass Aggregate Guide

What is Foam Glass Aggregate?

Foam glass aggregate (also known as foam glass gravel or FGA) is a lightweight, thermally insulating aggregate made from post-consumer recycled glass. It’s a versatile building material that can be used in a variety of construction and industrial applications. Foam glass aggregate is used as lightweight structural fill in embankments and abutments, as thermal insulation under concrete slabs, and as lightweight fill in green roofs, among other applications. Foam glass aggregate is a durable solution to replace heavy aggregates and foam-based insulation materials. Its production processes support circular economy principles, diverting waste glass from landfills and turning it into a building material with minimal embodied carbon. 

History of Foam Glass Aggregate

Foam glass aggregate was first discovered in the early 20th century by a Soviet scientist, but its potential wasn’t fully realized until the late 1900s. The rise of high performance buildings and growing awareness of embodied carbon were key drivers of its increased popularity.

Early versions of foam glass aggregate made in the early 20th century were used as an industrial material in eastern Europe. During the early days of the United States’ recycling initiatives, the Environmental Protection Agency (EPA) published a study in 1977 in support of manufacturing foam glass insulation from waste glass. This study provided evidence that waste glass could effectively be transformed into foam glass insulation in both board and ‘pellet’ forms.

Physical Characteristics

High compressive strength – suitable for structural applications

Frost heave resistant – Will reduce impacts of of freeze and thaw

Produced from recycled glass – Categorized as ‘clean fill’

Water resistant – Closed cell structure facilitates drainage

Non combustible – Will not burn, nor propagate fires

Durable – Prevents rodents, termites, bacteria, and rot

Thermal insulation – R1.7 per compacted inch

Lightweight – 10 pounds per cubic foot

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Production

Processed glass aggregate is milled into a superfine powder and combined with a foaming agent. It’s dropped onto a belt and heated to 1,500°F at a specific thermal profile to soften the glass into a foam glass slab. At those temperatures, the foaming agent off-gases and the gases are captured in the foam glass slab, creating a network of closed-cell micropores. The foam glass slab exits the kiln and fractures into pieces due to temperature change. Over the next few minutes, the aggregate slab turns into aggregate pieces ranging from 1”-3” in diameter. The total firing and cooling process takes roughly an hour.

Foam glass gravel kilns are traditionally powered by natural gas. Glavel’s kiln has been electrified and powered with renewable energy, contributing to a low embodied carbon material.

Foam Glass Applications

Built Environment

Foam glass aggregate is used as subslab insulation as a lightweight, load-bearing thermal insulator. It contributes to the overall efficiency of a building’s envelope by eliminating thermal breaks and energy loss. It replaces both rigid foam-based insulation and stone in a subslab insulation system, reducing the associated labor and streamlining the subslab insulation process. Foam glass aggregate is inert and durable, making it ideal for projects that require thermal performance and structural integrity.

Green Roof Fill

Foam glass aggregate serves as a multi-functional layer in green roof systems, providing drainage and thermal insulation. Its lightweight nature reduces structural loads and eases the installation process compared to heavy aggregates or foam insulation. Foam glass aggregate supports building insulation and stormwater management, enhancing both the environmental performance of a building and the longevity of a green roof system.

Infrastructure

Foam glass aggregate is used as lightweight, structural fill in retaining walls, embankments, bridge abutments, and roadways. Its high compressive strength supports static and dynamic loads, while reducing load on surrounding areas. This makes it a useful material in challenging soil conditions or in places with strict weight requirements. Its non-leaching and closed-cell structure ensure long-term performance in challenging environments.

Foam Glass Aggregate Benefits

Building with foam glass aggregate incorporates sustainability into construction projects and helps builders, designers, architects, and construction professionals achieve carbon reduction goals. The environmental impact of foam glass aggregate goes beyond its production processes with recycled inputs and renewable energy. Its lightweight nature reduces transportation costs, with shipments of up to 130 cubic yards per load. Foam glass aggregate also streamlines labor and installation processes. It’s easy to handle and can be installed in high volumes by a small team.

Foam Glass Aggregate vs. Traditional Aggregates

When compared to traditional aggregates like crushed stone or gravel, foam glass aggregate stands out in several ways:

  • Weight: FGA is up to 85% lighter.
  • Insulation: Traditional aggregates provide minimal thermal benefits.
  • Embodied Carbon: Foam glass aggregate’s recycled glass inputs makes it a more environmentally responsible material than traditional aggregates.

OnLogic Case Study

One notable example of foam glass aggregate in action is OnLogic’s headquarters in South Burlington, VT.  Glavel played a role in achieving the project’s sustainability and performance goals. Its lightweight and insulating properties eliminated the need for traditional insulation, ensuring energy efficiency while providing the conditioned space necessary for employee comfort and consistent manufacturing processes. According to ReArch Company, the use of Glavel resulted in an 87% reduction in embodied carbon emissions compared to a traditional insulation detail.

 

Future Trends in Foam Glass Aggregate

As the demand for green building materials grows, foam glass aggregate is poised to play a key role in the future of construction. Innovations in manufacturing processes and applications are expanding its potential uses, while stricter environmental regulations drive adoption in infrastructure and construction.

Ready to explore how foam glass aggregate can enhance your next project? Contact Glavel to learn more and get started today.

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