Which cavity insulation material is right for your home?

1. Mineral Wool, 2. Fiberglass Batt, 3. Dense Pack Cellulose, 4. Closed Cell Spray Polyerthene Foam

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In North America, wood framing is the most common method for exterior wall construction. These wood framed walls are built with 2x6 studs, (1.5"x5.5") spaced not more than 16"-24" on center. The spaces between each stud are called "stud bays" or "cavities" and these cavities must receive insulation.

As a home owner looking to renovate or build a new house, you should have an understanding of the different cavity insulation materials available to you and the pros and cons of each. A choice will need to be made and if you don't discuss these options with your general contractor, the choice will be made for you.

There are 7 main criteria to consider when selecting the right cavity insulation for your home. I've listed these in order of importance to you as the home owner:

1. Price:  The average per square foot installed cost (material + labor) for the product.

2. Moisture Durability: How well the material responds to moisture intrusion and how the material helps or hinders drying of the wall cavity.

3. Installation Complexity:  This matters because the thermal performance of any insulation product can be greatly diminished if not installed properly. Certain products require greater care with installation to perform as they should.

4. Accessibility:  Homes evolve and renovations, modifications and repairs are all part of the life story of a home. The future ability to work around installed cavity insulation is going to be an issue you should consider.

5. Health and Chemical Exposure:  People spend most of their time in-doors surrounded by these materials. I would be doing you a disservice if I did not include a conversation about the toxicity of these various insulation products.

6. Fire Resistance:  What happens to these different materials when they are exposed to an open flame?

7. Thermal performance: How well does the material insulate? The thermal performance of an insulating material is described by its "R-value." The higher the R-value, the better the insulation will resist heat transfer.

You might be wondering why an article written about insulation lists thermal performance dead last in order of importance. Let me explain... Within a 5 1/2" thick 2x6 stud cavity, each insulation material can be used to construct a wall that satisfies the required energy code. Closed-cell spray foam may provide substantially more R-value per inch than fiberglass, cellulose or mineral wool, but that advantage has limited value when the objective is simply to achieve the required insulation level within a conventional wall assembly.