What this covers
Spray foam is mixed at the gun and expands to fill the cavity, so it insulates and air seals at the same time. Open-cell foam is softer and lighter; closed-cell foam is denser, resists moisture and adds some rigidity. The installer masks surfaces, sets up ventilation, sprays in passes to the specified thickness, and trims any foam that stands proud of the framing. Rim joists, basement walls, crawlspaces, roof decks and new framing are common places for it. Careful work keeps the layer even, keeps foam off wiring boxes and vents, and covers it with a thermal barrier where the code requires one.
When to call
- Drafty rim joists or a cold basement where the walls meet the floor framing.
- An attic you want to bring inside the conditioned space with foam on the roof deck.
- New framing in an addition or rebuild that needs insulation and air sealing together.
What to expect
- PlanFoam type, thickness and areas are chosen, and any required thermal barrier is noted.
- PrepareThe space is masked and ventilated, and occupants are told when to stay out.
- SprayFoam is applied in passes to the specified thickness and trimmed flush.
- CureThe foam cures and the space is ventilated before anyone goes back in.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
What is the difference between open-cell and closed-cell foam?
Open-cell foam is lighter and lets some moisture pass. Closed-cell foam is denser, resists water and gives more insulation per inch. The installer recommends one for the location and climate.
Do I need to leave the house during spraying?
Occupants usually stay out of the area during spraying and for a set period afterward while the foam cures and the space is ventilated. The installer gives you the re-entry time for the product used.
Can spray foam be left exposed?
In living spaces, basements and many attics, the code requires foam to be covered with a thermal barrier such as drywall or an approved coating. The installer follows what the code calls for.
Related: Air sealing · Wall insulation · Attic conversion · All insulation and energy
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