Required insulation

One of the most common questions we receive is about required insulation.

It's important to note that more insulation is always better, however, here are the bare minimums for our climate. For your convenience, we have included both metric (RSI) tables as well as tables converted to the old standard "R" values.

* For non-engineered slabs on grade, above a frostline. Greater requirements apply with heated floors (R12). Engineered slabs must meet requirements established by the designer.

The National Energy Code for Buildings applies to larger non-residential buildings. Essentially any non-residential building greater than 300 m² (3230 ft²) need to meet the requirements below. Most notably, the NECB requires significantly greater wall insulation - R23 for our area.

These figures are the requirements for the complete assembly. In a standard stud-and-cavity wall, the "thermal bridging" effect of the studs must be taken into account. For example, in a typical  2x6 wall, one can insert R22 insulation in the cavities, but the studs themselves only provide R 5.5 for the 1.5 inches of space each occupies, so the wall itself will be less than R22 overall.

However, for the average building owner, all of this is somewhat moot: NECB 2020 requires energy modelling for new builds and additions, which means sophisticated software will evaluate energy consumption to ensure long-term operating costs for energy are reduced as much as reasonable.

Insulation and renovations:

Renovations - especially partial renovations - can present something of a challenge when it comes to insulating existing buildings. For example, when tearing out an exterior wall in an existing 2x4 home, there are only three ways to bring that wall up to the required R17 effective value: foam in the existing cavity; add foam to the exterior; or extend the wall to create an effective 5-1/2" cavity and fill with R20 or R22 batts.

Our staff recognize that these options may not be possible from either a practical or a cost perspective. What we do ask is that in such situations, all attempts should be made to improve insulation value as much as possible.