Closed Cell Spray Foam Insulation

Closed cell foam is the dense, rigid one. It expands about 30 times, cures hard, and its cells are sealed off from each other, so air and moisture don’t move through it. It gives almost twice the R-value per inch of open cell and adds real strength to whatever it bonds to. That combination is why it is the standard on metal buildings and barndominiums across Texas.

What closed cell does

• Stops condensation on steel. Sprayed directly on metal panels, it keeps humid air off the steel, so the panels can’t sweat. This is the main reason metal building owners call us.
• Blocks moisture. At about 1.5″ and thicker it acts as a vapor retarder, which matters in crawl spaces and on steel.
• Adds stiffness. It bonds panels to girts and purlins and quiets rattling and oil-canning. In wood framing it adds racking strength.
• Packs R-value into thin spaces. About R-13 in 2″, where open cell would need 3.5″.

Where we use it

Metal buildings, barndominiums, steel shops, pole barns and crawl spaces all get closed cell. In houses we also use it on rim joists, on low-slope roofs with shallow rafters, on the ceiling of a garage under a bonus room, and anywhere the framing is too thin for open cell to reach the R-value you need.

How thick, and what R-value

Thickness	About	Typical use
1.5″	R-10	Steel walls, budget condensation control
2″	R-13	Metal and barndo walls, crawl spaces
3″	R-20	Metal roofs over living or cooled space
4″	R-26	Cold storage, high-performance roofs

Why it costs more, and when it is worth it

Closed cell uses about four times the material per inch of open cell, so it costs more per inch. On steel, there is no real alternative: open cell and fiberglass can’t stop condensation on the panels. In a crawl space it is the only spray foam we recommend. Under a house roof deck with deep rafters, open cell usually gives you the same comfort for less. See current rates on the spray foam cost page.

Closed cell questions

Is closed cell foam a vapor barrier?

At about 1.5″ and thicker, closed cell acts as a vapor retarder, which slows moisture enough to stop condensation on steel and keep crawl space dampness out of the floor. That is why the minimum we spray on metal is 1.5″, and most jobs get 2″ or more.

Can closed cell go under the roof deck of a house?

It can, and on a low-slope roof or where the rafters are shallow it is the better choice. On a typical pitched roof with deep rafters, we usually recommend open cell, because it costs less for the same comfort and lets a roof leak show up inside.

Can you spray closed cell on the outside of a building?

Not as insulation alone. Sunlight breaks down exposed foam, so foam on the outside of a roof needs a protective coating and is a roofing system in its own right. We spray foam on the inside of buildings.

Does closed cell foam make a metal building stronger?

It stiffens the panels and the connection between panels and framing, which makes the building quieter and more solid in wind and rain. It doesn’t change the building’s structural rating, so it isn’t a fix for a building that needs structural repair.