Ways to meet the new minimum code for insulating exterior walls in Ontario

When you are thinking about insulating your new custom home spray foam should be one of the main types of insulation that you should consider.

There are many different ways to insulate a home today; depending on where you live the building codes require you to do different things for different parts of the home. Insulation has changed so much in the last 10 to 20 years that a lot of people and contractors are having trouble keeping up.

In the province of Ontario the building code for exterior walls has changed in the last couple of years, several years ago they outside walls had to be R-20 to meet the minimum code requirement. Today the minimum code requirement is R-24.

There are several options for people to meet this new code; here are some of the most common ways:

• Owens Corning has come out with a new fibreglass batt that is R-24; this replaces their older batt that was rated at only R-22. This is the easiest and cheapest way to meet the new code.

• Add polystyrene insulation to the outside of the walls. Polystyrene with a normal R-22 batt will exceed the code requirements.  This works well because it insulates over the studs and not just between them eliminating thermal bridging. You have to plan in advance for this because adding the insulation to the outside of the building will require things like the windows to be installed farther out, making the build-outs deeper than normal.

• Add foil back foam board to the inside of the wall, foil back foam is denser then polystyrene so that it isn’t as thick. The foil works to reflect the heat back into the building helping the energy efficiency of the home. The foil back foam also covers the studs on the inside of the wall not just between them stopping the thermal bridging. This allows you to use the foil back foam as vapour barrier as well once you tape the joints, eliminating the need for super 6 plastic.

• Spraying closed cell foam in the walls, allows you to fill the entire cavity and increase the R-value to between R-35 and R-31, this makes the house extremely sound proof and air tight. Some municipalities will allow you to skip the vapour barrier when the walls are spray foamed.

• Another way to use spray foam is to butter the walls between the studs with a 2” of spray foam and then add a 4” roxal batt to bring the insulation up to between R-24 and R-28. This helps keep the price down compared to filling the entire cavity with spray foam.

• You can use a netting loose insulation in the outside walls. The process is rather simple, you install netting over the studs and then you blow loose fibre glass insulation into the wall cavities. The netting keeps the loose insulation from falling out and allows for a tighter fit between studs. This can give you an R-24 insulation rating.

These are the most common types of insulating for a 2x6 stick framed exterior residential house wall.

Rob Abbott
Operations Manager
Village Builders Inc.