Closed-Cell Spray Foam in Chattanooga

What closed-cell foam is

Closed-cell spray polyurethane foam is a dense, rigid foam in which the tiny cells are sealed. That structure makes it resist air, water, and vapor. HomeGuide lists closed-cell at about R-5 to R-7 per inch and about $3.00 to $5.00 per square foot installed.

Source: HomeGuide, Spray Foam Insulation Cost (December 2025).

Strengths

• High R per inch. Useful in thin cavities like 2x4 walls and rim joists.
• Air barrier. Seals gaps in one pass.
• Vapor retarder. At sufficient thickness, it slows vapor movement, which can be useful at the edge of the ground.
• Water resistance. It does not soak up water like open-cell or fiberglass.
• Rigidity. It can add stiffness to some assemblies.

Limits

• Cost. It costs more per inch than open-cell.
• Vapor control can cut both ways. In some assemblies, a vapor retarder in the wrong place can trap moisture. The assembly design matters.
• Hard to remove. If you later need to access framing, closed-cell is hard to cut out.
• Not a fix for leaks. Water from leaks, poor grading, or plumbing must be fixed first.

Where closed-cell is common around Chattanooga

Rim joists

The band of framing at the top of the foundation leaks air and is hard to insulate with batts. Closed-cell fills it in one pass. See rim joist spray foam.

Crawl walls

In sealed crawls, closed-cell on foundation walls insulates and air seals. ENERGY STAR recommends about R-5 sheathing or R-13 batt on crawl walls in zone 3. See crawl space foam.

Source: ENERGY STAR, Recommended Home Insulation R-Values.

Basement walls

Closed-cell is often used on below-grade walls because it resists moisture.

Thin walls

In 2x4 walls, closed-cell can reach higher R-values than open-cell in the same space.

Metal buildings

Shops and pole barns in Soddy-Daisy, Ringgold, and rural Hamilton County often sweat when humid air hits cold metal. Closed-cell on the inside of the metal reduces condensation. See garage and shop foam.

Fire protection

Like all foam plastic, closed-cell generally must be separated from living space by a thermal barrier, with specific rules for attics and crawls. See ICC, International Residential Code, Chapter 3 (Section R316, Foam Plastic).

Safety during installation

Stay out of the house during spraying and until curing and ventilation are complete. See U.S. EPA Safer Choice, Vacate and Safe Re-Entry Time for Spray Polyurethane Foam Application.

Questions to ask

• What thickness and R-value?
• Which product and blowing agent?
• How is the foam protected for fire safety?
• How is moisture handled in the assembly?
• What is the warranty?

Next steps

Compare with open-cell foam and read open vs closed. See costs. We serve Soddy-Daisy, Ringgold, Cleveland, and nearby. See our services.

A worked example

A 1950s home in Red Bank has an unfinished basement with block walls and leaky rim joists. After checking for water and fixing a downspout, closed-cell foam goes on the rim joists and the upper part of the block walls. The basement feels less damp and the floor above is warmer in winter. The foam is then covered as required for fire protection.

Thickness matters

Closed-cell is often sprayed in passes, with each pass limited in thickness by the manufacturer to control heat during curing. Spraying too thick at once can cause problems. Ask your installer how many passes they plan.

Blowing agents

Closed-cell foams use blowing agents to form cells. Newer formulations use agents with lower global warming potential. Ask which product will be used.

Closed-cell and electrical

Closed-cell foam can be sprayed around wires and boxes, but electricians should finish rough-in first. Moving wires after foam is hard.

When closed-cell is not the right choice

• Where an assembly needs to dry to the inside.
• On roof decks where open-cell meets the goal for less.
• Where future access to framing is needed.

Closed-cell under floors

In vented crawls, some homeowners spray closed-cell on the underside of the subfloor between joists. It air seals the floor and resists moisture, but leaves the crawl vented. In humid climates, sealing the crawl is often the better long-term approach. Ask your installer which suits your home.

Summary

Closed-cell foam earns its higher price where its strengths matter: at the rim, on crawl and basement walls, in thin cavities, and on metal buildings. Elsewhere, open-cell or hybrids may be the better value.

More closed-cell questions

What R-value is closed-cell spray foam?

HomeGuide lists about R-5 to R-7 per inch.

How much does closed-cell spray foam cost?

HomeGuide lists about $3.00 to $5.00 per square foot installed.

Is closed-cell spray foam a vapor barrier?

At sufficient thickness it acts as a vapor retarder, which can help at the edge of the ground but must fit the assembly design.

Where is closed-cell foam used most?

Rim joists, crawl and basement walls, thin walls, and metal buildings.

Can closed-cell foam be removed later?

It is hard to remove because it is rigid and bonds well, so plan access before spraying.

Why is closed-cell sprayed in passes?

Manufacturers limit pass thickness to control heat during curing. Spraying too thick at once can cause problems.

When is closed-cell not the right choice?

Where an assembly needs to dry inward, on roof decks where open-cell meets the goal for less, or where future access is needed.

Can closed-cell be sprayed under the floor in a vented crawl?

Yes. It air seals the floor and resists moisture, but sealing the crawl is often the better long-term approach in humid climates.

Is closed-cell worth the higher price?

Where moisture resistance, thin cavities, or high R per inch matter, yes. Elsewhere, open-cell or hybrids may be better value.