Open or Closed?

There is so much confidence in spray foam insulation that there is not much need for convincing. More people are realizing the short and long term benefits of using spray foam in their homes. But the question remains, open cell or closed for Central Texas?

My theory based upon my knowledge is that closed cell probably acts more as a vapor barrier because it is more dense than open cell. Since a vapor barrier is not recommended in our region I reasoned that the air barrier properties of the open cell would be preferred.

My own theories on the subject are fine but to really know what is best, I wanted to find a very knowledgeable person who has worked with foam long enough to know it’s properties and how it behaves. Kurt DeRuiter of DeRuiter Insulation Inc was both knowledgeable and kind to spend some time with me on the subject. In 2001, Kurt was instrumental in helping the city establish the code of certain applications of insulation by helping them understand the properties of foam versus other types.

Kurt first explained the properties of open cell and closed cell foam. Open cell foam has water as a blowing agent which creates small open balls, like whiffle balls with holes, in the foam. The cured foam has holes shaped like those in a sponge which create an air barrier and a higher perm rating of 3.6. Water can pass through open cell foam but air does not blow through it.

Closed cell foam has a blowing agent that is made of inert gas. The inert gas is encapsulated by urethane and the result is layers upon layers of tiny gas filled bubbles. Contrary to my theory, this makes it more of a vapor retarder not a vapor barrier. For a product to be classified as a vapor barrier it would have a perm rating of .006 and 1” thick of closed cell foam has a perm rating of 1.0.

In Kurt’s opinion, the open cell foam is the best for Central Texas in most applications. The main reason is that the cost comparison between 1” thick of closed is about 4-5 times more costly than 1″ of open. The R-value of 1” open cell is R3.8 and 1” closed cell is R7 so you get more R-value for your money with open cell.

Another reason for using open cell vs. closed cell, especially in a roof system is that since close cell would permeate very little to no water, you could have a roof leak for years that you would not know about until there was extensive damage. With an open cell application, the water would permeate through and the leak would be found quickly.

There are great uses for closed cell in wine cellars and in crawl spaces. With closed cell, you would be keeping in or keeping out the moisture with the vapor retarder.

The advantages of spray foam insulation are great and the most obvious one that bears repeating is the supreme insulating qualities. In a typical attic, temperatures can reach 145 degrees with ducts running through at 60 degrees. This is a 85 degree difference in temperature and is quite inefficient for cooling. In both the summer and winter, most of the conditioned heat or cooling loss is in the roof. With an open cell foam roof and sealed attic, the temperature of the attic is within 14 degrees of the heated and cooled space. What a difference!

I am so pleased to know that my theory was not too far off target; thank you Kurt for sharing your valuable knowledge of spray foam insulation.

Green Living Tips!

I welcome inspirations from your home to put into future newsletters. Email them to me; Cammi Klier. Thanks!!

This bit of green living encouragement comes straight from the Renewable Energy Roundup that was held in Fredericksburg this past weekend. I saw many people walking around with their own water containers and very few plastic water bottles. This was a very green inspired group of people! The stainless steel container can be found almost anywhere and comes in so many options with belt loop holders or flip top lids. Go buy one for your self before you buy another plastic bottle of water!