Open Cell Vs Closed Cell Foam Under Roof

Benefits of open cell spray foam.

Open cell vs closed cell foam under roof.

I started all this spf stuff under roof decks in the early 1980s. Both icynene open cell and closed cell spray insulation are effective insulators with both working as barriers for air leakage. Open cell foams will tend to leak closer to the point of entry making leaks easier to identify and locate. Closed cell or high density foam is a better insulator and will not take on water.

Less common of the two types of spray foam open cell is mostly used for residential and commercial insulation. Closed cell foam is higher density foam and a moisture barrier. Closed cell foam can be over three times that with a density of 1 75 pounds per cubic foot or more. Closed cell foam has a higher r value than open cell foam usually about 6 0 per inch.

Closed celled foams will perform better in terms of deflecting water away from interior elements but may allow leaks to go undetected longer. Open and closed cell foam insulation use a blowing agent to forms the cells within it. A foams r value is its resistance to heat flow or in other words how well they insulate. Open cell foams most commonly range from 5 lb to 7lb densities.

However open cell and closed cell have their different uses. Spray foam is categorized into two types open cell or closed cell. Common sense tell s me if this is valid marketing then what stops water vapor from moving through the foam under pressure. Open cell foam is just that open cell.

Stop with the stupid comments about open cell being better under a roof deck than closed cell because if there is a leak the leak either dries faster or you can see it sooner. The open cell material is more affordable compared to closed cell and expands more which makes it an excellent material for tight spaces and areas with nooks and crannies. It is often used for roofing on commercial buildings. Open cell is lightweight foam that is flexible and an excellent air barrier.

Chemical manufacturer s claim if a roof leaks water will migrate through the foam structure therefore not trapping the water. Open cell foams use water as a blowing agent. When it comes to insulating a home whether that s a roof insulation or floor insulation it is ideal to use icynene open cell spray foam. I m afraid i must digress from hoebeke builders opinion open cell foam will take on and hold water it is open.

As with all construction products installation is critical to the performance of the product. Let s not confuse open cell vs closed cell foam. Most open cell foam has a density of about 5 pounds per cubic foot.