How to Choose and Use Insulation

October 11, 2022

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This Old House general contractor Tom Silva explains the wide world of insulation

In this video, This Old House general contractor Tom Silva explains the wide world of insulation.

Choosing insulation

Cellulose insulation is composed of shredded newspaper treated with Boron. It’s blown into the wall cavities and has an R-value of about 3.6 per inch.
Closed-cell insulation forms a hard, rigid foam surface with an R-value of 6.0 per inch.
Open-cell insulation is blown into wall cavities as a liquid and within a few seconds it expands and hardens. It boasts an R-value of 3.6 to 3.8 per inch.
Insulation made from ground-up blue jeans comes in batts and installs just like fiberglass insulation. It has an R-value of about 3.2 to 3.6 per inch.
Fiberglass insulation fits into the stud bays and traps air to deliver an R-value of about 3.2 to 3.6 per inch. Be careful not to pack the insulation too tightly. It loses its effectiveness if compressed.
To block out moisture in extreme cold or hot climates, consider installing a polyethylene vapor barrier on the warm side of the wall.
A vapor retarder blocks most moisture, but still allows the insulation in the stud bays to breathe. Vapor retarder can be installed separately or it comes already attached to the insulation batts.
Open-cell and cellulose insulation don’t need vapor barriers, but can benefit from a vapor retarder in some climates. Closed-cell insulation doesn’t need a vapor barrier or retarder.