Best Insulation Choices for Green Building

Quality insulation is a cornerstone of an energy efficient building. It improves thermal performance, reducing energy consumption and wasted resources. In doing so, insulation makes a building greener not just at the time of its completion, but over the course of its lifetime. Conventional insulation choices, however, haven’t always been so green.

The most common types of insulation have poor environmental records. Alex Wilson, writing for the University of Waterloo’s Environmental Building News, outlines the environmental impacts of varying types of insulation, from their embodied energy to their impact on indoor air quality. Conventional insulating materials show significant cause for concern, even accounting for more recent environmental improvements such as the phasing out of CFCs and HFCs in polyurethane insulation.

Both fibreglass insulation and spray foams, for example, are highly energy-intensive to produce. They generate, as Wilson says, “multi-tiered” problems stemming from resource extraction and manufacture. VOCs that are off-gassed by spray foam insulation can also be a particular concern for homeowners.

This might sound disheartening because these are the types of insulation we’re most likely to find in our walls, at the home improvement store and in our contractors’ trucks. Fortunately, though, they’re not the only choices on the market. Let’s explore some more environmentally-friendly options.

Green Insulation Choices

First off, a quick note about what we mean by “green.” Some of these options will be made from natural and renewable resources, some will be recycled and recyclable and some will simply be less toxic materials. Everyone has their own criteria that are important to them when choosing sustainable products, so we’ll try to lay out any environmental concerns as we go.

Cellulose

Recycled paper often finds a second life in cellulose insulation, which is made of shredded paper fibres usually containing 75-85 percent post-consumer recycled content. You can find this in loose-fill form, or it can be sprayed in. It has an R-value of about R-3.5 per inch, which is comparable to fibreglass. Its real strength, however, is its density, which allows it to block air leaks more effectively than fibreglass.

It’s typically treated with boric acid or ammonium sulfate to make it fire-retardant. It’s more established and more common than some of the other types of insulation on this list, and is likely to therefore be less expensive.

Cork

This type of insulation comes in semi-rigid boards, with an R-value of R-3 to R-4 per inch. Cork is taken from the outer bark of mature cork trees in a specialized harvesting process that doesn’t harm the tree. Cork insulation usually comes from the waste generated by wine cork manufacturers. That waste is pressed into boards, and since cork is naturally anti-fungal, no extra chemicals are added.

Cork trees actually regenerate their bark over and over, making this a natural, renewable, recycled as well as recyclable and biodegradable product. It’s also a carbon sink, since it sequesters carbon and since cork production has entailed the maintenance of mature groves of trees over centuries. On the downside, it’s not common in Canada (although its popularity is rising), so it’s expensive.

Denim

Denim is a type of cellulose, being made from cotton. The insulation makes use of both recycled denim clothes and waste fibres from textile manufacturing processes. It can come as a loose-fill product or as a batt, and has an R-value of about R-3.5 per inch. At the end of its useful life, denim insulation can be recycled again, at least in theory.

Like cellulose insulation, denim is often coated with borate to make it fire-retardant and mould and pest resistant. It’s also expensive. Cotton has a terrible environmental record, so recycling it and recovering the industry’s waste is at least helpful in offsetting the giant carbon footprint that our cotton clothes come with.

Icynene

Icynene is a spray foam or pour-in insulation that can be made of castor oil, of all things. It’s more expensive than conventional blown-in options, although it’s also exceptional at preventing air leaks and doesn’t lose its R-value over time, which is something to consider. That R-value is R-3.6-R-3.7 per inch as a spray and R-4 as a poured-in product. This insulation is activated by water rather than a chemical agent, which reduces air pollution both indoors and out.

If you use Icynene, you can feel patriotic about it—it’s produced by one company, and that company is Canadian. Icynene is also manufactured as a petroleum-based product (which may or may not contain recycled plastics), so be sure to specify that you’re looking for a greener version.

Mineral Wool

Mineral wool insulation is made from molten materials such as rock, glass and iron ore slag, which is spun until it’s fibrous (hence the name). It typically contains 75% recycled industrial material, which is about the only reason it’s on this list. It has an R-value somewhere between R-3 and R-4.

Conventionally, mineral wool insulation has been made with a formaldehyde binding agent, but it’s possible to find formaldehyde-free products. This material is, nevertheless, highly energy-intensive to produce.

Mycelium

Maybe the most interesting material of the bunch, mycelium insulation is made from fungus. Fungal spores are combined with agricultural waste products like rice hulls and then poured into a mould. As the mycelium grows, its roots wind through the agricultural fibres and grow into solid blocks that resemble foam. Its R-value is R-3 per inch.

While the blocks are sterilized, they’re not flammable and therefore don’t require extra flame retardants. This is a natural, biodegradable product that’s in its infancy. While you might not be able to find it now, it’s worth keeping an ear out for.

Wool

Wool insulates as well in human homes as it does on sheep. It’s naturally fire and mould-resistant, and so doesn’t need additional chemical treatments, although it might be treated with a non-toxic pest-repellant. You can find it in wool batts or loose-fill. In batts, its R-value is about R-3.5, often higher. Loose-fill, it reaches in excess of R-4. To alleviate any concerns over animal welfare, sheep are not harmed by shearing.

A lot of wool insulation is produced with polyester binders, but 100% wool products are on the market. This is a less common type of insulation, which means that although the cost is expected to drop, it might be prohibitively expensive on anything larger than an outbuilding. Unless you have sheep.

Takeaway

With fibreglass and spray-foams dominating the market, it’s even more important to be aware of alternative insulation choices and to consider what you’re putting in your walls. After all, if you’re installing insulation in order to be greener, your insulation may as well be green.

Feature image: Dan Hamill; Image 1: Karolina Grabowska