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What’s the difference between open and closed cell foam?

Open Cell Foam Insulation is a somewhat porous material that can allow water vapor to penetrate the insulation, if the moisture differential is high and prolonged. Closed Cell Foam Insulation is non-porous with all of the voids closed to each other which makes it impossible for water vapor to pass through it. The vapor porosity of the two materials is the biggest difference and most important issue, but both are impervious to air transmission.

The other major difference between open cell and closed cell foam insulation is the density of the in-place foam. Open cell foams typically weigh about 0.5 lbs per cubic foot while closed cell foams have classically been 1.7lbs per cubic foot and up. Closed cell foams are stronger and denser allowing them to carry heavier loads. This is also one of the reasons that closed cell foam is quite a bit more expensive compared to open cell foam per board foot.

The final issue when discussing the differences between open cell and closed cell foam insulation is the insulating value or R value per inch of insulation. Our open cell foam insulation typically has average R values of about 3.6 per inch while our closed cell foam insulation has average R values of about 6.5. So you can see closed cell foam insulation can be almost twice the insulating values per inch.

Please speak with your spray foam contractor or Aloha Energy to determine the best type of foam for your application.

Posted in: Environmental, Spray Foam Insulation