How Long Does Spray Foam Insulation Last?

How long does spray foam insulation last when it's installed right?

Spray foam is a cured polyurethane plastic, bonded to the framing it was sprayed on. The industry's Center for the Polyurethanes Industry (CPI) says it "resists structural deterioration/decomposition over time and resists settling." Inside a wall or under a roof deck it sits in the dark, and if the building is kept dry, nothing is working to break it down.

CPI doesn't give a number of years; its advice is to ask the contractor or manufacturer. Some of the best real-world evidence comes from foam that lives outdoors. A roofing guide published by the Insurance Institute for Business & Home Safety (IBHS) and RICOWI says "maintained SPF roofs exhibit life spans in excess of 30 years," with the protective coating renewed every 10 to 20 years. That foam takes sun, rain and hail. Foam behind drywall takes none of it.

Manufacturers' warranties point the same way. One major manufacturer's closed-cell limited warranty, for example, says the foam will perform as stated on its data sheet "throughout the life of the building," if it's registered and installed by an authorized contractor.

What happens to R-value over time

Closed-cell: a small drop, mostly early

Closed-cell foam gets much of its R-value from the blowing agent trapped in its cells. Over time some of that gas diffuses out, and R-value drops a little. The change is fastest at first and slows down.

The rating already accounts for this. The FTC's R-value Rule requires tests on polyurethane foam to use samples that "fully reflect the effect of aging on the product's R-value." One standard lab method for that, CAN/ULC-S770 (adapted from ASTM C1303), estimates long-term thermal resistance (LTTR). According to the National Roofing Contractors Association's magazine, the LTTR represents the value after 5 years, which "corresponds closely to a 15-year, time-weighted average."

How big is the drop? In one manufacturer's lab tests of three 2-pound closed-cell foams, R-value fell less than 6 percent over the first year. When you compare products, use the aged R-value at the thickness you're buying. At R-7 per inch, a typical aged value for HFO closed-cell, 3 inches is R-21. See spray foam R-value per inch.

Open-cell: nothing to lose

Open-cell foam is blown mostly with water, according to a DOE Building America guide, and its cells are open to the air. There's no trapped gas to escape, so it doesn't go through the same aging.

Compared with fiberglass and cellulose

Settling isn't a defect in loose-fill. It's expected, and a good installer blows to the depth on the bag. But it's a real difference: foam bonded to the framing stays where it was sprayed.

What shortens spray foam's life

1. Sunlight. The IBHS/RICOWI guide says spray foam exposed to UV first darkens, then "the top surface skin will become friable," meaning it crumbles. Indoors, foam behind drywall or a coating never sees the sun. Foam left bare outdoors, or where the sun hits it every day, needs a covering or coating.
2. Water. Closed-cell foam doesn't absorb water, but the wood it covers can rot. DOE's guide warns that "when leaks occur in ccSPF they may not be immediately apparent." Open-cell foam can hold water. On a foamed roof deck, the roof itself is what you maintain.
3. A bad install. Off-ratio foam can stay sticky or crumbly. Passes sprayed too thick can crack or scorch, and foam sprayed on cold, wet or dusty surfaces may not stick. None of that heals. A seven-year Arizona State study of spray foam roofs found that "the contractor and the season when the roof was installed did affect the quality of the roofs." See off-ratio spray foam.
4. Physical damage. DOE's guide lists closed-cell at 22 psi compressive strength against under 2 psi for open-cell, so open-cell dents easily. Exposed foam in a shop or barn takes hits from equipment, and CPI notes that some pests may chew through foam over time.
5. Later renovation. Every wire, pipe or vent run through foam is a cut that should be sealed again.

How to check old spray foam

Use this list on foam that's been in place for a while, or when you buy a house that has it:

1. Edges. Foam should be tight to studs, rafters and the rim joist. Gaps or pulled-away edges are a warning sign.
2. Surface. Good foam looks even and uniform. Cracked, shrunken or discolored foam is a warning sign, and so is a surface that crumbles or feels sticky.
3. Firmness. Closed-cell foam should be rigid. Soft or spongy spots in closed-cell are a concern.
4. Smell. Long after the install, there should be no chemical odor. A lingering one needs checking (spray foam smell).
5. Wood and water. In an attic, look for stains or drips at foam edges, around chimneys, vents and skylights, and on framing below. After any roof leak, have the deck checked.
6. Thickness. A contractor can probe the foam to confirm the depth matches the paperwork. Don't cut into suspect foam yourself.
7. Paperwork. Find the product name, install date, warranty registration and lot numbers. FoamGuard records drum lot numbers on every job, and you can look up a FoamGuard warranty at foam-guard.com/warranty.

For a full guide to warning signs, see how to spot bad spray foam.

What the warranties cover

A "lifetime" product warranty covers the foam, not the job. The closed-cell warranty linked below is typical of what to look for:

• Registration within 90 days of the install.
• Installation by an authorized contractor with trained applicators, following the manufacturer's written instructions.
• A remedy of repair or replacement "at the cost of the material only," without labor or removal.
• Exclusions for improper installation, fire, storms, floods, abuse and later alterations.

That's why the installer's own workmanship warranty matters. FoamGuard's installs carry the manufacturer's product warranty plus A Craftsman's Promise, our 5-year craftsmanship warranty.

Want a number for your own project? Price My Project or call (814) 208-3478.