With building codes increasingly tightening the building envelope and boosting insulation levels, and federal and provincial grants incentivizing energy retrofits, it’s important to know the basics when it comes to insulating a home. Here’s a quick overview of the options for sealing the gaps.
Fibreglass batts are the most affordable and one of the easiest options to install, making them the most common choice. Batts can also be used on interior walls and floors for soundproofing. You do need to install a continuous air and vapour barrier on exterior walls to avoid moisture issues. Note also that airborne glass fibres can irritate the eyes, nose, throat or skin.
Foam boards are made from a variety of materials – polyurethane, polystyrene and polyisocyanurate to be specific – and come in a range of sizes and thicknesses. R-values range from about three to eight per inch. Its density means it also acts as an air barrier, but you need to tape all the seams. With sealed joints, products with the right compressive strength can also work as an effective radon barrier in basement floors.
Insulated concrete forms
Insulated concrete forms, better known by the acronym ICFs, are increasingly showing up on jobsites for everything from foundations to the entire exterior structure up to the eaves. And why not, their Lego-like assembly makes it lighter and easier to install than wooden forms. Plus, you end up with an insulated foundation when the job is done. Again, you’ll pay a premium for the ease of installation and added R-value.
The cheapest and easiest way to insulate an attic is with blown-in cellulose. Rent a blower such as Owens Corning’s AttiCat and you can complete attic insulation in less than a day. The total R-value is only limited by the height in the attic available to fill; in some cases, you can get up to R-80. The biggest drawback is that it’s messy, so the attic space can’t be used for storage. It’s also an irritant, so long sleeves, gloves and a respirator should be worn during application and when working with and among the material.
Contractors are increasingly turning to foam as an all-in-one solution for insulation and an air and vapour barrier, in part because it offers the highest R-values per inch. You need specialty equipment and training to install it, so you’ll pay a premium. Also, the jobsite will be off-limits for a few days during and after installation while the product off-gases.
Filling in the gaps
There are single-use disposable cans available but, for contractors, it’s most cost-effective to buy a decent-quality spray foam gun and use larger refill cans. Be aware that some foams are air sealants and some are insulation which do not air seal. In some tough locations, such as between windows and walls, air sealing and insulation are important, and a mix of foams, tapes and other sealants may be necessary. Just don’t make the rookie mistake of taking an empty bottle off without immediately replacing it. Foam will harden inside the gun and then it’s garbage.
To ensure proper attic ventilation when using blown-in insulation, install attic baffles along the rafters at least a couple feet up from the eaves, used in conjunction with roof venting.
There are a variety of speciality tapes designed to seal air gaps on specific applications – from poly air and vapour barriers and foam boards to sill plates.
Caulking and weatherstripping
While technically not insulation, caulking and weatherstripping kits provide the final finish for sealing up the building envelope. After all, airtightness is the biggest bang for the buck when it comes to cost-effective energy efficiency.
Mineral wool batts
Mineral wool batts are available in a variety of sizes designed to fit standard stud-wall centres, and they’re easy to cut to size and shape if needed. Their rigid structure also means they won’t sag in the wall cavity like fibreglass can. Like fibreglass, you need a continuous air and vapour barrier and the material can be an irritant. Its density makes it a great option for sound- and fireproofing between floors or units in a multiplex.