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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.

Required insulation, southern New Brunswick
Metric Imperial
Attics 8.67 49.2
Cathedral ceilings 4.67 26.5
Walls 3.08 17.5
Floors (over unheated) 4.67 26.5
Attics 8.67 49.2
Cathedral Ceilings 4.67 26.5
Walls 2.97 16.9
Floors (over unheated) 4.67 26.5

It's important to note that these values are the bare requirement for Code-compliant construction. Note, for example, that cathedral ceilings require less insulation than attics: we suggest contractors/builders exceed this particular requirement.)

Note also that 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*.

In 2x4 wall construction, fibreglas cavity insulation is insufficient, as the net will be R10 (for 12" on centre studs) to R11 (for 16" on centre studs). For this reason, many renovations will specify either three inches of commercial spray foam (which runs about R7 per inch) or the addition of exterior solid foam to bolster the overall insulation of the home. It's also the reason most new home specify 2x6 construction.

(*Math: 16" OC wall, comprised of 14.5" of R 22 and 1.5" of R 5.5. (14.5/16)* R 22+ (1.5/16)* R 5.5 = R 19.9 + R.51=R 20.4 effective.)