Commercial buildings use Foamglas cellular glass insulation where ordinary foam boards fall short. It’s made of glass blown into tiny sealed bubbles, so it won’t burn, won’t soak up water and blocks water vapor completely. It’s also strong enough to sit under concrete slabs and heavy roof decks. The trade-off is a modest R-value, about R-3.4 per inch, and a much higher price than foam board.
Most homeowners never see cellular glass, but builders of hospitals, cold storage buildings and plaza decks know it well. Our Grizzly Insulation Co teamswork on commercial projects around Denver, so here’s a look at what makes this material different.
What Is Foamglas Cellular Glass Insulation?
It’s rigid insulation made from glass that’s been foamed into millions of tiny closed cells. FOAMGLAS is the best-known brand name, now made by Owens Corning. The boards look a bit like dark gray pumice and cut with a saw.
Because it’s 100 percent glass, there’s nothing in it that can rot, burn or feed mold. Our blog on what R-value means explains how its R-value compares.
What Makes Cellular Glass Different From Foam Board?
Its properties come straight from the glass. Green Building Advisor’s information on Foamglas insulation lists these figures:
Property
Cellular glass
R-value per inch
About R-3.44
Vapor permeability
Zero
Fire
Noncombustible (ASTM E136)
Compressive strength
About 90 psi standard, higher grades available
Cost
About 2.5 times XPS per board foot
Foam boards like XPS and polyiso have more R per inch but burn and slowly absorb some moisture. See our blog on the highest R-value insulation for the comparison.
Where Do Commercial Buildings Use Cellular Glass Insulation?
In spots where failure is expensive. Common uses:
Under heavy concrete slabs, where the insulation has to carry big loads without crushing.
Roof decks and plazas, including green roofs and decks with foot traffic.
Below-grade foundation walls, where groundwater is constant.
Cold storage and freezers, where vapor must be stopped completely.
Buildings with strict fire rules, since it’s noncombustible.
Vapor and liquid water can’t pass through the sealed cells. A manufacturer rep notes in the same article that the cut cells on the outside of a board can hold water, though, and exposed boards below grade need protection from freeze-thaw damage.
You may hear that cellular glass “never needs protection.” That isn’t so. If a project were ours, we’d still cover it with a protection board below grade and keep drainage working. For how foam compares, see whether closed cell foam absorbs water.
Is Cellular Glass Used on Pipes and Industrial Equipment?
Beyond buildings, cellular glass is common on industrial piping and tanks, including very cold lines and hot process lines. It doesn’t burn, it doesn’t soak up liquids, and it keeps its shape across a wide temperature range.
Those same traits are why engineers pick it for freezer floors and cold storage walls, where moisture would ruin other insulation over time. Our blog on does insulation keep cold in explains how insulation works on cold spaces.
Why Isn't Cellular Glass Used More in Homes?
. At roughly two and a half times the price of XPS, with less R per inch, it’s hard to justify in a typical house. Foam board, mineral wool and spray foam do the job well for far less.
It makes sense in homes only in special cases, like a slab that must carry heavy loads or a basement with constant water. For most Denver homes, closed cell spray foam or XPS covers those needs. See closed cell spray foam R-value.
Does Cellular Glass Work in Denver's Climate?
It doesn’t lose R-value in the cold the way some foams can, and freeze-thaw is only a risk on unprotected exposed faces. That makes it a good fit for Denver plaza decks and below-grade walls that see snowmelt every spring.
What Are the Alternatives to Cellular Glass Insulation?
It depends on what job the cellular glass would be doing. If you need strength under a slab, high-density XPS or EPS rated for the load is the usual budget swap. If you need fire safety, mineral wool board is non-combustible and costs far less. If you need a full vapor seal on odd shapes, closed cell spray foam does that and seals air leaks too.
On most Denver commercial jobs we mix materials. Cellular glass goes only where its strengths really matter, and cheaper insulation covers the rest. Our spray foam insulation teams handle walls and roofs, and our crawl space insulation team covers below-grade spaces in homes.
How Long Does Cellular Glass Insulation Last?
A very long time. Glass doesn’t break down, and it gives pests nothing to eat. As long as it isn’t crushed or left exposed to freeze-thaw, it keeps its R-value for the life of the building. Our guide on pest-resistant insulation covers other materials pests avoid.
Use Foamglas Cellular Glass Insulation Where Nothing Else Will Do
Foamglas cellular glass insulation earns its price where loads, water and fire risk are high. For everyday walls and attics, other materials give more R for less money. For more ways to tighten a building, see energy efficient insulation.
Planning a commercial project in Denver? Grizzly Insulation Co can help you choose the right material. We’re BPI Certified and an Xcel Energy rebate partner.
Why Commercial Buildings Use Foamglas Cellular Glass Insulation
Commercial buildings use Foamglas cellular glass insulation where ordinary foam boards fall short. It’s made of glass blown into tiny sealed bubbles, so it won’t burn, won’t soak up water and blocks water vapor completely. It’s also strong enough to sit under concrete slabs and heavy roof decks. The trade-off is a modest R-value, about R-3.4 per inch, and a much higher price than foam board.
Most homeowners never see cellular glass, but builders of hospitals, cold storage buildings and plaza decks know it well. Our Grizzly Insulation Co teamswork on commercial projects around Denver, so here’s a look at what makes this material different.
What Is Foamglas Cellular Glass Insulation?
It’s rigid insulation made from glass that’s been foamed into millions of tiny closed cells. FOAMGLAS is the best-known brand name, now made by Owens Corning. The boards look a bit like dark gray pumice and cut with a saw.
Because it’s 100 percent glass, there’s nothing in it that can rot, burn or feed mold. Our blog on what R-value means explains how its R-value compares.
What Makes Cellular Glass Different From Foam Board?
Its properties come straight from the glass. Green Building Advisor’s information on Foamglas insulation lists these figures:
Foam boards like XPS and polyiso have more R per inch but burn and slowly absorb some moisture. See our blog on the highest R-value insulation for the comparison.
Where Do Commercial Buildings Use Cellular Glass Insulation?
In spots where failure is expensive. Common uses:
Our commercial insulation team works on projects like these.
Is Cellular Glass Insulation Really Waterproof?
Vapor and liquid water can’t pass through the sealed cells. A manufacturer rep notes in the same article that the cut cells on the outside of a board can hold water, though, and exposed boards below grade need protection from freeze-thaw damage.
You may hear that cellular glass “never needs protection.” That isn’t so. If a project were ours, we’d still cover it with a protection board below grade and keep drainage working. For how foam compares, see whether closed cell foam absorbs water.
Is Cellular Glass Used on Pipes and Industrial Equipment?
Beyond buildings, cellular glass is common on industrial piping and tanks, including very cold lines and hot process lines. It doesn’t burn, it doesn’t soak up liquids, and it keeps its shape across a wide temperature range.
Those same traits are why engineers pick it for freezer floors and cold storage walls, where moisture would ruin other insulation over time. Our blog on does insulation keep cold in explains how insulation works on cold spaces.
Why Isn't Cellular Glass Used More in Homes?
. At roughly two and a half times the price of XPS, with less R per inch, it’s hard to justify in a typical house. Foam board, mineral wool and spray foam do the job well for far less.
It makes sense in homes only in special cases, like a slab that must carry heavy loads or a basement with constant water. For most Denver homes, closed cell spray foam or XPS covers those needs. See closed cell spray foam R-value.
Does Cellular Glass Work in Denver's Climate?
It doesn’t lose R-value in the cold the way some foams can, and freeze-thaw is only a risk on unprotected exposed faces. That makes it a good fit for Denver plaza decks and below-grade walls that see snowmelt every spring.
What Are the Alternatives to Cellular Glass Insulation?
It depends on what job the cellular glass would be doing. If you need strength under a slab, high-density XPS or EPS rated for the load is the usual budget swap. If you need fire safety, mineral wool board is non-combustible and costs far less. If you need a full vapor seal on odd shapes, closed cell spray foam does that and seals air leaks too.
On most Denver commercial jobs we mix materials. Cellular glass goes only where its strengths really matter, and cheaper insulation covers the rest. Our spray foam insulation teams handle walls and roofs, and our crawl space insulation team covers below-grade spaces in homes.
How Long Does Cellular Glass Insulation Last?
A very long time. Glass doesn’t break down, and it gives pests nothing to eat. As long as it isn’t crushed or left exposed to freeze-thaw, it keeps its R-value for the life of the building. Our guide on pest-resistant insulation covers other materials pests avoid.
Use Foamglas Cellular Glass Insulation Where Nothing Else Will Do
Foamglas cellular glass insulation earns its price where loads, water and fire risk are high. For everyday walls and attics, other materials give more R for less money. For more ways to tighten a building, see energy efficient insulation.
Planning a commercial project in Denver? Grizzly Insulation Co can help you choose the right material. We’re BPI Certified and an Xcel Energy rebate partner.
Frequently Asked Questions
About R-3.44 per inch.
It’s noncombustible, so it won’t burn.
Yes. It’s strong enough for heavy slabs.
It’s made from glass in a high-heat process, and it costs about 2.5 times XPS.
No. It already blocks vapor completely.