Benefits of Cellulose vs. Fibreglass Insulation

Fibreglass and cellulose are two very common insulating materials. At Above All Insulation, we’ve weighed the pros and cons of each material, and are proficient installers of both products. Here’s what we’ve learned:

For wall cavity insulation, fibreglass batts are a very good choice when you’re building or renovating. They offer excellent insulative value, and come conveniently sized to fit 2×4 and 2×6 studs, on 16” or 24” centres. Fibreglass is a proven product that’s known to be safe when properly handled, and is non-combustible. Roxul™ batts are made of mineral wool and offer improved mould and fire protection compared to fibreglass batts.

Homes built before 1930 often have empty exterior wall cavities. When the walls and siding are in good shape and when it is uneconomical to take the walls apart to install batt insulation, dense-pack cellulose is the way to go. By selectively drilling holes through the exterior stucco or wood siding, cellulose can be dense-packed into the cavities and can provide excellent wall insulation (R14) that prevents air infiltration better than batting.

For attic insulation, we have taken an extensive look at the pros and cons of both blown-in fibreglass and blown-in cellulose, and we have decided that cellulose is the way to go.

Cellulose is made from recycled newspaper, treated with a safe fire retardant (boric acid powder) that also makes it repellent to rodents and other pests, and prevents mould from growing. It performs as well as or better than fibreglass on all counts, and is friendly to the environment, both inside and outside of your home. But the real deciding factor for us is performance, especially in very cold weather.

Because of air convection (travel of air through the insulative material) fibreglass actually loses R-value in cold temperatures. Tests have shown that if the difference between inside and outside temperatures is high enough, blown-in fibreglass can lose up to 50% of its ability to keep warm air in your house. This is because the cold attic air is able to settle down between the glass fibres. On the other hand, because cellulose is three times more dense than fibreglass, it is able to block air infiltration much more effectively, and can actually become a better insulator when the mercury heads for the bottom.

In a climate like Winnipeg’s, where the temperature ranges well into the “frigid” category for much of the winter, we think that cellulose is the obvious choice for attic insulation.