Last Updated: Jan 21, 2021
If you want a comfortable home that is less expensive to operate, putting some thought into your home’s insulation is helpful.
Insulation can help address the many ways a home can lose heat (for example, through walls, the floor, and roofs). Insulation works by putting a thermal barrier between the inside of a house and the outside of it. Better insulation means less heat is transferred between the inside and outside of the house, saving energy and money on both heating and cooling. Ensuring your home has effective insulation is an essential part of achieving the benefits of a highly energy-efficient home.
There are several different insulation options on the market. The most common include fiberglass batting, cellulose insulation, spray foam insulation, and mineral wool insulation.
There are also less common insulation types that are worth considering. These types include, among others, sheep wool and foam glass insulation. While foam glass isn’t typical in North American residential building projects, the material has been around for decades. Foam glass was invented in the 1930s. Pittsburgh Corning (later Owens Corning) invented a patented version of foam glass called Foamglas® that decade.
Foam glass is, not surprisingly, given its name, made from glass. The manufacturing process involves crushing glass into a fine powder. This powder glass is then manufactured into foam glass using a process that involves heating and adding a foaming agent, often carbon-black.
The result is a strong, highly durable building material made out of glass and tiny “cells” or bubbles of gas (mostly filled with CO2) that contribute to foam glass's insulating properties.
Foam glass is a hard, solid building material with exceptional strength and load-bearing properties. It can be used as sub-slab insulation and can replace both the aggregate and thermal layers underneath a building.
Foam glass is also lightweight, which means you can use it as roof insulation, with particular value in buildings with green roofs. Green roofs can be quite heavy, so the lightness of foam glass is advantageous for green roofs.
The strength and insulation properties of foam glass also make it useful for large infrastructure projects like roads and pipes. In some cases, you can use foam glass as a heat and sound insulator around pipes.
Although residential use of foam glass is more common in Europe, it is less common to use foam glass in North America. Although, if a homeowner is committed to the idea of foam glass, it makes an excellent replacement for extruded polystyrene.
Foam glass has an insulation R-value of 3.4. An R-value is a measure of the ability of a material to resist heat flow. The R-value of foam is about 30% lower than extruded polystyrene. However, foam glass can still be considered to have excellent insulation properties as a building material.
The advantages of foam glass as a building material are in both the manufacturing and use phases of the material.
When compared to extruded polystyrene, the foam glass manufacturing process and materials have less environmental harm. Foam glass manufacturing does not require the use of a potent greenhouse gas that is necessary to make extruded polystyrene. Foam glass is also sometimes made from recycled glass, which further reduces its environmental impact.
Foam glass is made mostly of glass, which means it does not burn. This fire-resistant property is an advantage of foam glass in itself. Also, toxic brominated flame retardants are not necessary when manufacturing foam glass. Avoiding toxic flame retardants protects both workers who manufacture the foam glass and homeowners who use it from exposure to toxic chemicals.
Health concerns about air quality are also a problem with some forms of spray foam insulation options, and foam glass does not have these health concerns because it is made of fire-resistant glass and is inert.
As a building material, foam glass has the advantage of being water-resistant, and it won’t break down at all when exposed to water. Also, foam glass is pest-resistant, meaning wood-boring insects like termites or ants cannot break down the material. These properties make foam glass a long-lasting building material, which can make it a more sustainable option than other insulation types.
The most significant disadvantage of foam glass, particularly in North American markets, is the price. It is more expensive than other forms of insulation on a per-unit basis.
However, foam glass can serve more than one role because it is insulating and porous (meaning water can get through). And while foam glass is porous, it does not break down with water exposure. Therefore, foam glass can replace two other building materials – those used for insulation and drainage. For example, foam glass can replace both the aggregate needed for drainage and polystyrene insulation when used under a slab foam. As a result, foam glass can become more cost-competitive in some building contexts.
The other disadvantage of foam glass is that it is not yet a widely used residential building material in North America. It can be hard to find for use in residential construction. Many builders may not yet know how to work with the material in residential contexts. Therefore, a homeowner may need to work with builders as they figure out how to use the material.
While foam glass is more common in Europe, in early 2019, there was news of two foam glass companies in North America making the push on foam glass fill in the U.S. market. Aero Aggregates uses 100% post-consumer glass to create a foam glass aggregate as a superior backfill in construction projects. Glavel is a Vermont-based company that offers several foam glass products for larger infrastructure projects. The use of these foam glass products can reduce these projects' carbon impact compared to projects using more traditional kinds of fill and insulation.
Owens Corning, the original Foamglas® company, operates in North America. It has a range of foam glass products. However, Owen Corning has exited the U.S. residential foam glass market because of cost issues and a lack of large orders.
Overall, foam glass insulation offers environmental and health benefits as insulation in both large infrastructure projects and homes. From a lower-impact, healthier manufacturing process to properties that make it resistant to fire and pests, foam glass has many benefits that homeowners will appreciate.
However, if a homeowner in North American is interested in using foam glass insulation as insulation in their home, it will take some work. Doing some research by reaching out to foam glass manufacturers and connecting with local builders, and asking about foam glass insulation is one place to start.
Dr. Kate Knuth is founder, strategist, and writer at Democracy and Climate LLC; and a fellow at the University of Minnesota Institute on the Environment. Kate was the first chief resilience officer for the City of Minneapolis and founding director of the Boreas Leadership Program. She served six years in the Minnesota House of Representatives, where she championed clean energy, climate, and toxic chemical policy reform policy. Kate also served six years on the Minnesota Environmental Quality Board. She earned a PhD from the University of Minnesota, a MSc from Oxford University, and a BA from the University of Chicago. She was a Fulbright Fellow in Norway.