Komorowski’s Korner by Richard Komorowski: Insulation – February 2, 2010


There are lots of ways of looking at your home, e.g. “Home is where the heart is”, “Home Sweet Home”, and so on. For many of us, our home is the biggest single financial investment we’ll ever make, so it had better be a good one.

For the engineer or building contractor, a home is a system designed to keep us warm and dry in winter, and cool and dry in summer. We’ll be looking at homes from this perspective in the next few columns.

Energy conservation is becoming so important these days that the Ontario Building Code devotes a whole section (Part 12), laying out the minimums required for any home built in the province – it is illegal to build any home that does not meet these minimum requirements.

These minimums go far beyond what was once required. At one time, a house could be built using 2 x 4 studs in the walls, and fibreglass batting for insulation, for a total wall insulation of R12 (RSI 2.1). Typically the attic would be R20 (RSI 3.5), and there would be no insulation whatever in the basement. No permit would be issued for such construction these days.

Insulation is the primary factor in building a warm, dry, cost effective home. The following table shows the Ontario Building Code’s minimum insulation values for houses currently being built. As of January 1, 2012, the minimum values will be even higher, as shown in brackets in the table.

Building element exposed to the Exterior or to Unheated Space Minimum RSI Value Required
Zone 1 Less than 5000 Degree Days Zone 2 More than 5000 Degree Days Electric Space Heating Zones 1 & 2
Ceiling below Attic or Roof Space 7.00 (7.24) 7.00 (7.24) 8.80 (9.00)
Roof Assembly without Attic or Roof Space 4.93 (5.21) 4.93 (5.21) 4.93 (5.21)
Wall other than a Foundation Wall 3.34 (3.80) 4.22 (4.67) 5.10 (5.55)
Foundation (basement) walls enclosing heated space 2.11 (2.40) 2.11 (2.40) 3.34 (3.63)
Floor, other than slab-on-ground 4.40 (4.70) 4.40 (4.70) 4.40 (4.70)
Slab on ground, containing heating pipes, ducts, tubes or cables 1.76 (2.11) 1.76 (2.11) 1.76 (2.11)
Slab on ground, not containing heating pipes, tubes, ducts or cables 1.41 (1.76) 1.41 (1.76) 1.76 (2.11)
Basement floor slabs located more than 600 mm below grade

Note: The values shown are the metric RSI values. To get the Imperial “R” value, multiply the RSI value by 5.678.

As you can see from the table, different parts of the house need more or less insulation. Most heat tends to be lost through the roof, followed by the outside walls, which is why the code calls for the most insulation in these parts.

Attics are easy to insulate as space isn’t an issue. As long as proper ventilation is maintained, you can pile it up as high as you want to get the required RSI value. Not only that, you can use relatively inefficient, but very economical, fibreglass batting or blown in cellulose. Right now is a good time to see if you could benefit by adding insulation to the attic – just go outside and see how much snow stays on your roof, compared to the neighbours’.

Basement walls are also relatively easy to insulate, because there is almost always sufficient space to apply the insulation. Although the basement isn’t so vulnerable to heat loss as the roof or outside walls, because of its relatively large size and ease of access, it is very cost effective to insulate here.

The outside walls are no doubt the biggest challenge. To get to the insulation, you’ll have to go through the drywall from inside the house, or tear off the siding, shingles or whatever on the outside. Upgrading the insulation here is not for the faint-hearted, but if you are considering replacing the siding, it can be well worth it.

It’s highly unlikely that you’ll be able to upgrade your home to Passive House standards. Depending on the location and climate, the Passive House has a roof of at least RSI 9, and walls of about RSI 7, and much better windows than are easily available here.

However, any upgrades you make will pay for themselves with increased comfort and fuel savings. As an added bonus, according to the Royal Bank, “on average, North American homes increase in value by 5 to 10% once energy efficient renovations have been made.”

Finally, a note of caution: Don’t go adding insulation anywhere in your home unless you know what you are doing. There are a lot of other considerations to take into account, such as moisture control and vapour barriers, fire safety, ventilation, and even the structural integrity of your house. If you’re not sure, talk to a qualified contractor or energy inspector, and check the Ontario Building Code.

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