What is Closed-cell and Open-cell Spray Foam Insulation

The days of the big pink bats of fiberglass insulation are past – spray polyurethane foam insulation is now the standard due to it’s superior insulative properties. Spray foam comes in two primary varieties, open-cell and closed-cell. It’s important to understand the differences between the two when making a decision about which to use. The following guide can help.

How Spray Foam Works

One of the greatest benefits of spray foam is that it can be added after construction is complete, so it works exceptionally well at adding insulation to older homes. The process of installation is relatively simple:

  • Holes are drilled in the drywall near the top of the wall between studs. These are the holes that will be used to apply the spray foam.
  • The spray foam components are mixed in a special tank attached to a mixing and application gun. As the components mix, the chemical reaction occurs that creates the foam.
  • The mixing and application gun is inserted into the hole and the foam is forced into the wall cavity. It expands to fully fill in the space.
  • The hole is patched and painted over, so that you can’t tell that the installation took place.

Choosing the Right Type of Foam

As previously mentioned, you have a choice between closed-cell and open-cell foam. The following will help you understand the benefits and limitations of each.

Open-Cell Foam Insulation

  • R-value: 3.6 per inch.
  • Average cost: Approximately .65 cents per board foot.
  • Vapor permeable, so not suitable for open installations (such as unfinished attics).
  • A greener option as it contains less petroleum products compared to closed-cell foam.
  • May require the installation of a vapor retarder in cold climates.

Due to its lower insulation value and the fact is is vapor permeable, open-cell foam is best suited to closed installations, such as finished walls, in mild climates. If you want foam insulation but have environmental concerns, using open-cell foam with a good vapor barrier may provide sufficient insulation for your needs.

Closed-Cell Foam Insulation

  • R-value: 6.5 per inch.
  • Average cost: about $1 per board foot.
  • Vapor retarders, so it is suitable for open installations.
  • Contains hydrofluorocarbons, so it is not an eco-friendly choice.
  • Can be used in conjunction with fiberglass batt insulation to increase insulative value of the batts.

Overall, closed-cell foam is the better insulation in colder climates where more R-value is needed. If you have environmental concerns, your insulation installer can install a thin layer of the closed-cell foam. This will act as a seal against air leakage while providing some insulation. When used in conjunction with traditional batt insulation, the result is better insulative qualities than what you would get with just fiberglass batts alone.

Can Your DIY It?

You may have noticed small cans of spray foam insulation at the hardware store. While these are suitable for small jobs, such as insulating around a door frame, the actual job of insulating an entire home or room is better left to the professionals. The process of properly mixing the chemicals to form the foam requires training and finesse. Spray foam can also be messy, and it can be difficult to predict how much it expands in a wall cavity without experience. Trying to do this yourself could lead to gaps in the insulation or damage to your wall boards.

Don’t let cost be the only deciding factor when choosing an insulation. In the long run, making the right choice now will result in energy savings for the life of your home. Compare the types of spray foam insulation side by side to make the choice that works best for your climate and needs.

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