What is the R value of open cell foam?

Asked By: Xiuying O hanlon | Last Updated: 11th May, 2020
Category: home and garden indoor environmental quality
4.9/5 (42 Views . 20 Votes)
about R-3.7 per inch

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In this regard, which is better closed or open cell foam insulation?

Closed cell foam has a higher R-value than open cell foam, usually about 6.0 per inch. This higher rating makes closed cell foam better at keeping heat in or out of a structure. Open cell foams have an R-value of around 3.5 per inch.

Subsequently, question is, what is the R value of 2 inches of spray foam? Open-cell spray foam absorbs and holds water. It has a lower R-value per inch than closed-cell foam and is vapor-permeable. The R-value is R-3.5 to R-3.6 per inch, so filling a 2×4 cavity yields about an R-13.

Considering this, what is the R value of 3.5 inches of spray foam?

Generally speaking the rule of thumb is the higher the R-value, the greater the insulating power. Focusing on spray foam insulation materials, there is a difference between the two main types. According to industry publication, Fine Home Building , the R-value for open-cell spray foam is between R-3.5R-3.6 per inch.

Does open cell foam need a vapor barrier?

Open cell spray foam is not a moisture vapor barrier, and will allow moisture to pass. So, if you're considering spraying foam to the roof deck of your new or existing home, you want open cell. If there's a roof leak, water will pass through the foam, and you will quickly be able to find your problem.

31 Related Question Answers Found

Does open cell foam absorb water?

Open-cell foam can absorb more water than a closed- cell product when submerged (although some open-cell foams absorb much less water than others).

Does spray foam stop water?

Using expanding polyurethane foam is one of the best ways to stop water leaks because the foam will expand into the cracks and help prevent future leaks. Expanding foam bonds to any type of surface and will quickly and effectively solve your water leak problems.

Does spray foam insulation cause moisture problems?

Spray Foam Myth: Insulating with spray foam insulation at the roof line will cause moisture problems with the roof sheathing. In an unvented attic scenario, to limit air leakage as well as any associated condensation at the roof line, a continuous air barrier is required.

Is expanding foam water resistant?

Product Q&A
Moisture-curing, self-expanding foam adheres to all common building materials. Resistant to water, heat and ageing. Ideal for filling large holes, voids, gaps around window and door frames and around exterior pipes.

How thick should spray foam insulation be?


The thickness of spray foam really depends on where it's being applied and what you're trying to accomplish. Now generically speaking, we usually recommend open cell spray foam to be 6-inches on a roof deck or ceiling and 3-inches in the walls.

Is spray foam insulation worth it?

The EPA's Energy Star Association has shown that monthly energy bills can be cut by up to 20% when air leaks are sealed and efficient insulation is installed. The initial cost of spray foam insulation is well worth the investment, when factoring in the overall savings that will be headed your way over the long term.

Does Spray Foam cause mold?

Sealing the attic is probably the most critical, in terms of counteracting moisture. As a product, spray foam insulation does not attract mold. And unlike wood or metal, spray foam does not rot, rust or deteriorate. It will control indoor humidity and condensation, and therefore prevent mold from growing and spreading.

Why is spray foam so expensive?

Spray foam is more expensive for several reasons: 1) The material is a thermal plastic; a by-product of crude oil. As the price of oil goes up, so does the price of spray foam. 2) Essentially, it's a high performance product and the price reflects it.

What is the R value of 1 inch Styrofoam?

Choose the right type of rigid foam for your needs
When choosing rigid foam insulation, you have three main options: Polyisocyanurate: Known as polyiso for short, polyisocyanurate foam has the highest R-value per inch (R-6.5 to R-6.8) of any rigid insulation.

Can you spray foam the underside of your roof?


Open- or closed-cell spray foam is applied to the underside of the roof sheathing, and additional fiberglass or cellulose insulation is blown in as a cost-saving method for meeting high insulation requirements and filling in the cavity space between the rafters to the ceiling deck.

Can I spray foam myself?

If you're thinking about buying a do-it-yourself spray foam insulation kits for your home, fire officials and those in the industry recommend you think again because of safety and fire issues. Spray foam acts as a great insulator and vapour barrier, but it's made up of chemicals and needs to be handled with care.

How long does spray foam insulation last?

With proper application, Spray Foam will last the lifetime of your home. Even roofing applications will last upwards of 30 years, with proper long-term maintenance. Spray Foam insulation adheres extremely well to virtually all substrates, and maintains its rigidity once dry.

Where should you not use expanding foam?

Spray Foam Around Windows and Doors is A-Ok
But it can actually push the jamb inward, making them impossible to open. Avoid this by using minimal expanding foam. It's formulated to fill the space around windows and doors without excess expansion. Look for cans labeled for use on windows and doors.

Is spray foam better than fiberglass?

Spray foam insulation fills all spaces, preventing air from escaping. It acts as an air barrier. Like cellulose insulation, spray foam insulation is significantly more efficient than fiberglass and has a higher R-value.

What should the R value be for exterior walls?


Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces. See the Department of Energy's (DOE) ranges for recommended levels of insulation below.

Can you put rigid foam insulation between studs?

Installing Foam Board Insulation Between Studs. Rigid foam board insulation can be used throughout the home, but most often it is found in basement walls. Any insulation is usually better than no insulation, as long as that insulation does not create more problems for you later on.

Can I spray foam over mold?

Closed cell foam will kill mold. It cooks it. Molds cannot survive the exothermic heat and the ensuing encapsulation.