Should I use spray foam insulation or stick with fiberglass?

I’m assuming that you are either building a new home or an addition to a home. That’s because adding spray foam insulation to an existing house is hard, especially in the wall cavities. Access to the wall cavities in an existing home is difficult or impossible due to the fact that the drywall or plaster is covering them. Unlike some types of insulation, spray foam cannot be installed through a small hole like blown-in insulation. The cavity must be completely open in order for the foam to be applied with the spray gun.

Just to be sure, the cavities I am referring to are formed by the 2×4 or 2×6 studs that make up the framing of the exterior walls. The back of the sheathing, which is either plywood, OSB, or real wood boards, is visible from the inside. The studs are usually 16 or 24 inches apart and are in front of the sheathing. The space between the studs is where the insulation is installed. Here’s a picture for reference:

This picture is actually not a wall. Its the bottom of a roof inside an attic.

So the short answer to your question is yes, it is worth it to use spray foam insulation. Here is a list of some of the Advantages:

  • Saves energy operating costs. 30-50% per year
  • Reduces air and moisture infiltration-resulting in a more consistent temperature
  • Reduces dust and pollen infiltration
  • Adds structural strength to the building
  • Reduces the likelihood of mold
  • Reduces noise
  • Reduces ice damages
  • Reduces HVAC capacity requirements
  • R-values remain stable over time
  • It has the highest performance of all insulation
  • It is permanent and will not sag or settle

Here are the Disadvantages:

  • The upfront cost is higher than conventional insulation
  • It is not generally a Do-it-Yourself project
  • The installation process is longer
  • The process could be messier

Having said all that, I think the decision hinges on the cost and the payback period. Spray foam will cost more than standard fiberglass insulation. The exact difference is hard to say because it varies in different parts of the country. But once you find out how much more it will cost, divide that amount by 4. That’s because it usually takes 4 years for the savings in fuel costs, due to the better insulation, to equal the additional cost of the foam. However, after that period of time is over, the savings in fuel are like money in your pocket.

The bottom line is you need to know in advance if you are going to stay long enough in the home to reap the rewards of the better insulation. It’s true that all of the other advantages, such as reduced dust and pollen, and better structural rigidity are available to you from day one. But if you’re not staying long enough to achieve the payback period, you need to decide for yourself if these other advantages are worth it for you. If money is no object then the spray foam insulation is definitely the way to go. Good Luck!

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