Know your insulation

Choose the insulation option that's right for your home

By Allan Britnell

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Board stiff
There are a number of different rigid insulations in varying thicknesses on the market. There are two common types. Expanded polystyrene is fairly loose white beads, not unlike the shipping material your tablesaw was packed in. It has an R-value of four. The other type is extruded polystyrene, the pink or blue boards you see in the hardware store. Extruded boards have an R-value of five. There are also boards made from fibreglass and other minerals, but these are less common. Others, such as Johns Manville’s polyisocyanurate boards, are faced with foil sheathing.

In new construction, boards are often used in conjunction with batts to achieve required R-values. An R-5 board on the exterior combined with R-12 batts in the wall cavity gives an overall rating of R-17. “Putting foam on the exterior of a wall reduces the majority of the drafts that would come through the wall, particularly around electrical outlets,” says Goyda. Another bonus: installing the boards doesn’t have the itch factor associated with batts.

The boards are easily cut with a utility knife and are simply nailed in place or glued directly to walls with adhesive. If the panels don’t interlock, the seams should be taped. And, as with batts, you need to install some vapour barrier on the warm side of interior walls.

It is important to note that the fumes from burning rigid insulation are toxic, so cover them with a fire-resistant material such as 1/2″ gypsum board. Then there’s the material cost. Polystyrene boards with an R-value of eight or less retail for $0.50 to $0.75 per sq. ft.

Canned heat
There are two types of canned foam insulation: polyurethane and latex. Both are easy to use but have very different properties. Latex remains pliable after installation and can be cleaned up with water. You can remove uncured polyurethane foam with acetone, but once it gets on your fingers you’re stuck with it until it wears away. Use gloves.

WHAT R YOU TALKING ABOUT?
The “R” in “R-value” stands for “resistance” to heat transfer. The higher the number, the better the insulation will be at keeping the heat in (or out). In Canada, we also use the metric equivalent, RSI. (If you’re feeling patriotic and would like to convert, RSI = R x 0.1761.)



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