Where I live in rural Ontario, there are plenty of old-timers who grew up in old, cold farmhouses. They’ll all tell you that, as a kid, it was no big deal to wake up on a winter morning, go downstairs to the kitchen and find an inch of ice on the water bucket by the wash basin. Winter was an indoor phenomenon back then, and they used twice as much energy trying to heat those old houses and didn’t even keep half as warm as we do now. Insulation is the difference. We have good stuff. They didn’t.
Broadly speaking, insulation can be divided into two families: fluffy fibre-based insulations, and rigid boards and sprays. The fluffy fibre-based stuff is the most common, and it’s also where you’ll find the most variety.
The two mainstay products in the fibre category are fibreglass and, more recently, mineral wool. Both are made like cotton candy. Inert materials such as reclaimed glass, basalt rock and recycled slag are melted, and then spun into fibres as they cool. The thin streams of hardened material form fibres that are pressed into batts or packaged as loose-fill insulation.
Fibreglass and mineral wool batt insulation offer the most economical, most widely available insulation options going, and that’s why they’re the most common across Canada. It’s what you’ll find in building supply outlets everywhere, but like most things in life, there are alternatives. If you’re looking for insulation that’s made from plant or animal products with minimal environmental impact, there are several choices.
Sheep’s wool insulation The market value of raw sheep’s wool has been so low for so long that lower grades of the stuff are now being made into insulation for walls and attics. Think of it like a sweater for your home. Not to be confused with mineral wool, sheep’s wool fibres are bonded together with polyester resins to form batts and rolls. You don’t need a mask when installing wool insulation, and like a good pair of wool socks, it can absorb and release moisture.
Denim insulation Who would have thought there were enough discarded jeans on the planet to support an entire home insulation sector? Denim fabric is really just cotton, and it’s made into batts and rolls for use in wall frames and attics. Denim insulation is about 30 percent better at blocking sound than fibreglass, but it’s harder to cut accurately than rockwool—the nicest batts of all to cut and fit. The big drawback with denim is cost and availability. You’ll pay almost as much for one batt of denim as you will for half a bale of the kind of mineral wool, or rockwool, you’ll find stocked at building supply outlets.
Soy spray When it comes to insulation, spray foam works fabulously well because it both insulates and stops air movement. A given R-value of spray foam delivers far more real-world energy savings than the same R of fibre insulation. The thing is, people are afraid of spray foam in general, because if it’s not applied correctly, it can cause short-term off-gassing of harmful chemicals. This is where soy-based spray foam comes in. A portion of the product is soy oil, so it’s considered safer than straight synthetics. It still needs to be applied with care to achieve effective results. Current performance of soy isn’t quite up to the insulation performance of conventional closed-cell spray foams.
Straw bales This isn’t really an insulation material so much as a wall construction option. Making walls from compressed bales of straw instead of studs offers lots of insulation value (typically R-40 and up), plus the ability to automatically moderate interior moisture levels over the seasons. The challenge with straw bale construction is preventing moisture migration into the material during construction, especially before the bales are fully protected behind plaster and a roof.
Personally, it’s not clear to me that any of the insulation alternatives are more environmentally sound than the kind of mineral wool/rockwool you can get readily at any building supply outlet. Also, denim, sheep’s wool and soy spray foam aren’t typically carried at building supply yards, and they cost so much more than mainstream alternatives that very few people buy them. Ordinary rockwool insulation is made from waste products, it works really well, it’s available everywhere, and it doesn’t cause itching or kick up dust during installation. I’m convinced that this is a case of the ordinary, non-flashy, off-the-shelf insulation product being an environmentally sound choice—at least that’s where facts and experience has led me.
Regardless of which insulation you choose, use lots of it. It’s pretty much impossible to use too much. Canada delivers some of the widest swings in seasonal temperatures of any place in the world, so insulation is particularly essential for home comfort and energy responsibility. Just think of frozen water buckets by the wash basin, and you’ll realize how lucky we are to have plentiful and effective insulation.