Open-Cell vs Closed-Cell Spray Foam
Spray foam can help with comfort and air leaks, but **open-cell** and **closed-cell** foam are not the same product. This guide explains the difference in plain language so you can ask better questions and compare written estimates with confidence.
Intro
If you are comparing spray foam options, the main question is usually this: Which type fits my home, my climate, and my budget? Open-cell and closed-cell spray foam both expand after application, but they perform differently.
One is lighter and usually lower cost. The other is denser, has a higher R-value per inch, and can help in tighter spaces. If you are still deciding whether spray foam is the right fit at all, it also helps to compare it with other insulation types and review typical insulation costs.
The short answer
Open-cell spray foam is usually chosen when you want air sealing and insulation at a lower typical cost, and when there is enough space to install more thickness. Closed-cell spray foam is usually chosen when you need more R-value in less space, want a denser material, or are insulating an area that may need stronger moisture resistance. The best choice depends on the part of the home, the target R-value, local code, climate zone, access, and budget.
How they differ
Both products are spray-applied insulation, but their structure is different.
Open-cell foam is softer and lighter. It expands a lot, which can help it fill cracks and gaps. It usually has a lower R-value per inch than closed-cell foam.
Closed-cell foam is much denser and more rigid. It expands less, but it gives you a higher R-value per inch. R-value is a simple way to measure how much the insulation slows heat flow. Higher R-value means better resistance to heat moving through that area, but more is not always better past the recommended level for your climate.
Because closed-cell has more R-value in less thickness, it is often considered when space is limited, like certain walls, rim joists, or rooflines.
Where each one may make sense
The right product often depends on where it is being installed.
Open-cell foam may be considered in interior applications or larger cavities where there is room to build up thickness and the goal is air sealing plus insulation.
Closed-cell foam may be considered in areas where you want more R-value in a thinner layer, or where the installer recommends a denser product because of the location and moisture conditions.
This does not mean one type is always better. A good plan depends on the assembly being insulated, local code, and whether the job also includes air sealing, ventilation changes, or removal of old insulation. For some homes, blown-in or batt insulation may be a better value than spray foam.
Ask each installer to explain:
- Which spray foam type they recommend for that exact area.
- What R-value the job is expected to reach.
- Whether the estimate includes air sealing and prep work.
- Whether old insulation removal is included, if needed.
- Whether permits are required locally.
Cost, estimates, and hiring carefully
Closed-cell spray foam is typically more expensive than open-cell spray foam, but the real price depends on the size of the area, the R-value target, the material used, home age, access, regional labor, and whether old insulation must be removed first. Treat online numbers as estimates, not quotes.
When you compare bids, do not look at price alone. Make sure each estimate lists the area being insulated, the foam type, and the final R-value in writing. It is also smart to review how to vet an insulation installer before you choose.
Always hire licensed and insured insulation installers, verify that license and insurance yourself, and follow local permit and code requirements.
What to do next
If you think spray foam may be a fit, start by narrowing down where you want insulation work done: attic, walls, crawlspace, basement, or rim joists. Then compare at least a few written estimates from licensed and insured installers.
Thermline is a free matching service that helps homeowners connect with local insulation installers. You can get matched and ask for estimates that clearly state the spray foam type, scope of work, and target R-value.
If you want a broader overview before deciding, you can also read more about spray foam insulation options.
Open-cell foam is softer and usually costs less, but it has less R-value per inch. Closed-cell foam is denser and usually costs more, but it gives more R-value in less space.