Not all insulation materials are the same, and they are not always interchangeable. A basic understanding of how walls work will help you understand what you can reasonably expect building materials to do for you when they are part of a wall assembly. If you have a working knowledge of building science then forge ahead, if not, check out this video first to learn the basics.
Understanding the physics behind how walls work is the key to designing well-insulated, airtight and durable wall systems.
Recycled Content: 80% to 100%
Method and form: Cellulose consists of shredded newsprint and is non-toxic, recycled and generally local. It’s great for attics, you can blow it to whatever depth you want (with proper ventilation) and there are no seams to allow heat loss. It’s also an excellent choice packed into walls because it allows little air infiltration and it’s fire and insect resistant.
R value: 3.66 per inch
Notes: All around this is the best choice for performance and environmental impact, but not recommended for basements due to its sensitivity to moisture.
Recycled Content: About 20%
Method and form: Batts are most common but it’s available in rigid. Reasonably low impact in production; raw materials are abundant; it offers good R value and reasonably good soundproofing.r
R value: 2.9 - 3.8 per inch
Notes: Fibres are volatile and installation can irritate the skin. Be sure to wear a mask, gloves and goggles. Make sure it is well installed- It doesn’t perform well if compressed, and gaps around studs and headers can actually encourage air convection causing heat loss.
Fibreglass is moisture sensitive and should not be installed where it will be exposed to moisture. Despite how commonly it can be found insulating foundation walls, it should never be installed against a cold concrete wall. See our pages on basement mold for more on this.
Rockwool mineral fiber insulation:
Recycled Content: there is a minimum of 75% industrial waste in stone wool insulation, often as high as 90%. The most common commercial manufacturer is Roxul, so that tends to be its common name on job sites.
Method and form: Batts or rigid panels, the batts are an excellent replacement for fiberglass (as seen in the main image above). Rock wool can be more costly per batt but has a higher R value than fibreglass per inch; less health risks during installation; easier installation; it performs better for fire and sound and is less harmful to the environment. Rock wool ComfortBoard rigid board insulation comes in various thicknesses starting at 1 ¼ (R5). Installed in conjunction with batts it can be a great replacement for foam as a thermal break.
Rock wool batts can be either specifically designed for insulation, or specifically designed for soundproofing. Insulation batts are not rated for soundproofing, but still outperform most other materials for sound reduction. Be sure to get the right product for the right application.
Rock wool in interior walls reduces sound between rooms and floors, as well as offering fire protection.
Below grade durability : as the climate warms, termites are moving north into Canada. Termites love foam insulation but the fibers in rock wool cut them, so they leave it alone.
Note: Rockwool insulation is a favourite of ours because of its durability and versatility. It is completely permeable to and unharmed by moisture, so there is less risk of damage during installation as well as during its operational life. It is hydrophobic (meaning it will not absorb water and moisture), so it can get wet without causing great concern. Once it dries it will maintain it's original R value. Given the chronic water and humidity problems that plague basements, stone wool is a much more suitable product for basement wall insulation than fiberglass.
Straw bale homes:
Recycled Content: Straw bale walls are the used stalks of grains, so they are generally 100% recycled and act as carbon storage so this will significantly reduce the overall ecological impact of your home.
Method and form: Traditionally it’s been done as stacked bale walls that are then covered in mud, and now prefab straw panels are beginning to show up on the market. You won’t find them at the big box stores, but they’re out there. A home in Peterborough, Ontario will be using them in an attempt to be the greenest home construction in Canada, success of that project will likely earn straw panels a bit exposure.
Notes: Be sure to research techniques well, being an organic material straw bales are highly susceptible to moisture damage and must be kept completely dry during construction. We really want to stress this, because this is a sensitive building technique and the stakes are pretty high if you don't do it right.
Bale walls have a very high R-value (around R40) and make for about as environmentally responsible a building material as you can get. But it is extremely labour intensive for sealing, so hopefully you have lots of friends that like playing with mud.
Excellent for soundproofing
Foam boards: Expanded (EPS) vs. Extruded (XPS)
XPS (Extruded polystyrene) refers to the coloured solid foam panels you most often see on the outside of buildings under construction. It offers a higher density and higher R-value per inch than EPS (expanded polystyrene) but because of its lower cost, EPS offers more R-value per dollar spent.
Manufacturers of XPS and EPS claim both products can be recycled, but a complete life cycle analysis shows EPS having a better overall environmental impact when compared to XPS, as EPS can be recycled in many more ways at the end of its usefulness. Read more about foam.
Expanded Polystyrene Foam (EPS)
Recycled content: Not very high.
Method and form: Comes in panels, 2x8, 4x8 and other dimensions, with variable thicknesses.
R value: 3.6 to 4.2 per inch.
Notes: EPS is the only commercially available foam insulation panel that is at all vapour permeable, which can be an advantage in some applications, as can those that are vapour impermeable.
The common blowing agent for EPS is pentane gas, which is ozone safe but has a global warming potential (GWP) 7 times greater than carbon dioxide. This is significantly lower than other types of foam, so we recommend it as the preferred choice of foam whenever possible.
Excellent for below grade applications, both inside and out. EPS is unharmed by moisture, and allows a certain amount of moisture to pass through it.
Extruded Polystyrene Foam (XPS)
Recycled content: Minimal at best.
Method and form: Comes in panels, 2x8, 4x8 and other dimensions.
R value: 5 per inch
XPS acts as a vapour barrier and air barrier.
Blowing agents are 1430 times worse than carbon dioxide, exponentially worse than EPS. For ecological reasons rather than performance, we recommend limiting its use when possible. A combination of polyethylene and EPS can offer the same vapour protection as XPS, more affordably and with significantly less impact on climate.
XPS is durable and unharmed by moisture, so it works well below grade.
S.PU.F. (Spray Polyurethane Foam)
Recycled Content: Minimal at best. Some are advertised as ‘soy based’ but there is so little soy content compared to the ecological impacts, that it borders on green washing. Use it for its excellent properties, but don’t fool yourself into thinking your home is insulated with tofu, because it most definitely is not.
Method and form: Urethane is sprayed on, and structurally solid to the point that you can walk on it in about 20 minutes.
R value: 6 per inch
Notes: SPUF acts as a vapour barrier and air barrier; blowing agents are also much worse than carbon dioxide and EPS. Off-gasing can be an even greater concern than other products as chemicals are mixed onsite, so no off-gasing takes place in manufacturing facilites and different stages of transit, but rather all in your home.
Method and form: commonly in 2x8 or 4x8 sheets
Performance: R6 - 6.5 and even higher are the claims of some producers, but independent researchers say it is more accurately calculated at about R5.6 per inch. Read more here.
Polyiso can be a great product in some applications but has some notable limitations. It is moisture sensitive, so it is important that it not be exposed to weather during construction or its service life. Panels come with foil membranes on either side to contain gas, though it will leak out eventually, reducing R values.
The stated performance is R6 - 6.5 per inch, but this is somewhat misleading as that is only at warmer temperatures. The performance starts to drop significantly below 10°C, and its performance at much lower temperatures (-20°C and below) is abysmal, hardly better than wood. A great product for interior use, but it must be on the warmer side of a wall assembly to do any good at all.
In the right environment (warm and dry) polyiso is one of the preferred foam products as the performance is high but the GWP is low, similar to that of EPS. Be aware that the foil membrane acts as a vapour barrier, and taped can act as an air barrier as well.
Cotton insulation (denim)
Recycled Content: 90-100% recycled. Use your GWG’s to lower your GHG’s
Method and form: It comes in batt form like fibreglass and stone wool. It performs better than fiberglass during high winds and at low temperatures; it is extremely effective for sound absorption and thermal performance; easier installation than fibreglass; no protective gear needed; it contains 10% boron-based fire retardant (a natural non-toxic mineral),and it's resistant to fungus, mold, and pests.
R value: 3.4-3.7 per inch
- Notes: It takes less energy to manufacture than other types of traditional insulation, contains no chemical irritants, and is completely safe and easy to install by homeowners. It’s not too common in the Canadian market yet, so it might be expensive if your lucky enough to even find it.
Thermal foil vapour barrier:
We’re including this with insulation, mostly to make clear its proper applications. Thermal foil refers to a bubble wrap with foil that acts to reflect infrared heat in certain situations. For it to work properly there needs to be an air space on the warm side.
It is an effective (if expensive) vapour barrier, and if you install a second layer of strapping for an air space, it will reduce infrared heat loss. Exactly how much is hotly debated and depends a a couple of factors - how it is installed and where it is installed within the wall assembly. Whether or not you will get your money out of it is questionable.
The place NOT to use it is anywhere that it will have no air space, like underneath a concrete basement floor as insulation. I say this because it has been used for this purpose, and is completely ineffective. It would do no harm and still work as a vapour barrier, but it is a waste of money buried in concrete. See our pages on basement slab insulation for more on how best to stay warm below grade.