Insulation options and tips

Save on energy bills by improving your home's insulation

By Steve Maxwell

Sheets of rigid foam

Photo by Steve Maxwell

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Insulating your home effectively may seem simple at first glance, but it can be more complicated than it looks. To improve the insulation in your home and save on energy bills, you will need to know your options and what to watch out for.

Prevent condensation

Condensation is a hidden danger in most insulation situations, at least here in Canada. Vapour barriers and air-sealing strategies are crucial. Vapour barriers are not just for keeping out cold drafts. There’s a more important function.

Air-sealing strategies inhibit the movement of warm, moist indoor air into insulated wall cavities and attic spaces. If this movement happens unhindered during the winter, most of the gaseous moisture within the leaked air will condense within the cold wall as it cools, forming droplets of water in the midst of your insulation and wall framing. This is not good. Preventing the destructive process of infiltration, cooling and condensation is why a polyethylene vapour barrier must be installed on the warm side of all exterior walls and ceilings. The hitch is that it has to be completely sealed to work properly. Air can get through the tiniest of cracks.

To help achieve vapour-proof results, use acoustic caulking to seal all vapour barrier joints as they come together. You’ll also find factory-formed plastic liners to extend the seal around, under and behind electrical boxes. These liners are the only practical way to keep condensation out of wall framing.

Consider foam insulation

Spray foam is both an excellent insulation and a first-rate air sealant for preventing drafts from leaking in around windows and door frames. You can hire someone to spray foam over large areas, buy cans for filling big spaces or get small pressurized cans with a rigid application nozzle that allows you to inject foam into cracks ranging from 1/8″ to 4″ wide.

foam extender

Foam extender. Photo by Steve Maxwell

Most formulations expand considerably, which is why low-expansion foams are best for windows that might be bowed inward and damaged by foam expansion pressures. Whichever type you use, don’t overfill the area and don’t miss the target.

The trick to working neatly in tight quarters is to slip a length of a large-diameter drinking straw over the rigid nozzle of the spray can. This setup makes it possible to fill tight spots that would otherwise go empty. Choose a straw that slips over the nozzle snugly and stays there with friction. Wrap some electrical tape over the joint, just to be sure.

A hacksaw blade taken out of the usual saw frame is the best tool for trimming excess foam ooze-out after it has hardened. Acetone removes the foam while it’s still sticky, but nothing gets it off after it’s cured. Always wear safety glasses when spraying any kind of foam.

Rigid sheets of extruded polystyrene foam boards aren’t usually applied to exterior stud walls during construction and renovation, but that’s changing. Building code upgrades have changed to require higher levels of wall insulation, and that’s why builders are using more foam. There are two reasons rigid foam makes sense for DIY renovations, too.

First, rigid foam a great insulator. The R-5 per inch delivered by most foam is a powerful addition to between-stud batts because foam provides an insulation layer that’s unbroken by wall studs.

Another advantage of foam sheets is their ability to reduce the chances of condensation building up. The foam sheets keep the stud cavity warm in the winter, reducing the possibility of condensation in areas where the vapour barrier or air sealing might be less than perfect. If you choose extruded polystyrene boards with shiplapped edges, you’ll also boost the water resistance of your outer walls. Just be sure to orient the joints so they shed water like a shingle before you put new siding on.

The easiest, most economical optioninsulation

So, what insulation strategy returns the greatest savings for the investment? For many Canadian homes, it’s the simplest option of all—loose-fill insulation blown into the attic. At a minimum, add enough to bring you up between R-50 and R-60.

The most energy-efficient home I know stays warm all winter without a furnace or electric heat and boasts a whopping R-90 in the attic.

Insulating intelligently takes knowledge, planning and care. Get these details right and you’ll enjoy the warmest and cosiest payoff for your home-improvement investment.

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