Closed-Cell Foam or Open-Cell Foam?

Last week I discussed a misconception that some homeowners have of spray foam insulation in, Is That Stuff New?

This week I want to talk about closed-cell and open-cell foam, specifically, is closed-cell foam better than open-cell foam or is open-cell foam better than closed-cell foam?

Well, it’s not as simple as one being better than the other; closed-cell foam is the better choice in some applications and open-cell foam is the better choice in other applications.

Remember, open-cell foam has limitations:

• It’s not intended for exterior applications

• It’s not intended to be used in below grade applications

• It’s not designed for contact with bulk water

• And, it’s not a Type II vapor retarder

Closed-cell foam is more versatile than open-cell foam, so if any of these are design parameters, then yes, closed-cell foam is not only a better choice, it is the only choice. This means that exterior building envelopes, below-grade basements, wine rooms, pool houses and other applications with significant temperature and relative humidity differences, are all obvious closed-cell foam applications.

On the other hand, when used appropriately, open-cell foam wins the economic analysis every time. Both types of foam are air barriers and when installed at equivalent R-values (i.e. different thicknesses), closed-cell foam can easily cost twice as much as open-cell foam, because the cost per R of closed-cell foam is double that of open-cell foam, with no thermal performance difference.

So, because open-cell foam is more cost effective when installed at equivalent R-values, it’s payback timeframe is much quicker. This means open-cell foam is typically the better choice for interior applications that don’t require the additional physical properties of closed-cell foam; most often this includes interior building envelope applications, like wall cavities and attics, in climate zones 1 through 4.

That’s all for now, stay tuned next week as we continue to explore the interesting world of spray foam insulation.

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