Mike Holmes - Insulation Type Comparison


From Friday's Globe and Mail

July 27, 2007 at 12:00 AM EST

There are some things your house can't do without, and insulation is one of them, no matter what climate you live in.

You need to invest in the best-quality, best-performing and safest insulation you can afford. It will save you money in the long run.

All your exterior walls and the attic require insulation. It keeps the temperature inside your house even — not too hot in summer nor too cold in winter —and cuts the cost of heating and cooling your house. Proper insulation will have a huge impact on your energy bills.

Insulation is rated in terms of its R-value (a measure of thermal resistance — how well it resists heat loss and how effective it will be when installed). The higher the R-value, the greater the insulating power. Related Articles

But that isn't the only thing to consider. You also need to think about air movement, or air infiltration — and the moisture carried in the air. Moisture will reduce the effectiveness of insulation, and may create mould.

Insulation works because air is trapped within the insulating material — moisture will compress the material, removing the air, and reduce its effectiveness.

There are a variety of insulations that are safe, fire resistant and work well when they are properly installed.

Glass batt insulation

Standard fibreglass wool batt is probably the most common insulation — it's what most new homes are insulated with today.

Made from micron-thin strands of blown glass, it's inexpensive but it has to be installed very carefully, which can be its biggest drawback.

A lot of contractors just slap it up and push it into spaces that are too small for the amount being used, or too big, leaving gaps in the coverage.

Mineral wool batt insulation is made from basalt rock and recycled slag—it's non- combustible and will not burn or release toxic gases when it contacts flame.

It also provides an excellent acoustical barrier between rooms.

All batt insulations need a properly installed vapour barrier to prevent air movement. That means the top and bottom are sealed and tuck tape covers any hole or seam.

Glass batt insulation is designed to be installed between studs.

Also, the studs don't have the same insulation value as the batts, so you have will always have cold spots on the wall where the studs are.

Rigid Styrofoam

Some builders and renovators solve the stud cold-spot problem by adding rigid insulation in a continuous layer on the outside of the house. That provides a much better, uninterrupted insulation; it should be standard on any renovation if glass batting is being used between the studs.

Rigid polystyrene boards are great for insulating basement walls and floors. No vapour barrier is needed with rigid insulation.

Blown-in insulation

Usually used in attics between and over the ceiling joists, blown-in insulation can provide excellent insulation value at a reasonable price.

Make sure your contractor doesn't cover over the vents in the soffits if you are adding more.

Since the 1980s, when asbestos was banned from use in insulations, blown-in insulation has been safe, but some of the old stuff may still contain amphibole asbestos, which is a carcinogen.

As long as the installed vermiculite isn't moved, it won't harm you, but if you have it in your attic and you are about to undergo a renovation that will disturb it, you need to have it tested.

Go to the Health Canada website for more information.

Spray foam insulation

This urethane-based insulation is sprayed into wall cavities where it expands to fill every crevice.

It's insect resistant and provides more R-value in the same space than any other insulation.

Most important, it has to be installed by licensed contractors, so you have some assurance that the work will be done properly. I love this insulation, use it all the time, and recommend it.

There are two types of spray foam: open cell and closed cell.

The closed-cell foam has a higher R-value than open cell, and doesn't require the use of a vapour barrier because it acts as an air barrier — so it's really efficient.

Sprayed foam insulation doesn't shrink, sag like batt insulation can, or settle like blown insulation.

Some spray foams contain CFCs (chlorofluorocarbons) that are harmful to Earth's ozone layer, or off-gas formaldehyde — a potentially harmful volatile organic compound — especially right after application.

Greener alternatives

Soy-based spray foam insulations contain no urea formaldehyde.

Since they use water as a propellant, they emit no volatile chemicals, ozone or CFCs into the atmosphere.

Blue jean batt insulation, which is 85 per cent cotton, is an alternative to mineral or fibreglass. It's made from scraps of blue jeans left over in the manufacturing process. The remaining 15 per cent is made from plastic fibres that are treated with borate to retard flame, mould and mildew, and deter insects. Borate is less toxic than table salt.