Wall Spray Foam Insulation Alberta

Nominal R and effective R are not the same number

A 2x6 wall with R-20 batt is not an R-20 wall. Roughly a quarter of its area is wood, wood is about R-1.2 per inch, and the batt does nothing about air moving through the assembly.

Once framing factor and air leakage are accounted for, the effective performance of a conventionally batted Alberta wall is well below its nominal rating. The rating describes the material; the wall is an assembly.

Foam improves both terms. It air-seals, and it can be run continuously across framing rather than only between it.

Three ways foam gets used in walls

Full-cavity closed-cell. Highest R per inch, its own vapour retarder, structural contribution to the frame. The default where cavity depth is limited or where vapour control matters most.

Full-cavity open-cell. Cheaper per board foot, excellent air seal, better acoustically. Needs a separate vapour retarder detailed for the climate zone, which in Alberta means it must be designed rather than assumed.

Flash-and-batt. An inch or two of closed-cell against the sheathing for the air and vapour control, then batt to fill the remaining depth for R-value at lower cost. A pragmatic assembly that gets much of the benefit at a lower price, and a common choice in Alberta new construction.

See closed-cell and open-cell for the full comparison.

The parts of a wall that actually leak

Flat wall area is the easy part. Walls lose air at their edges and interruptions: the top and bottom plates, the corners, around windows and doors, at electrical boxes and penetrations, and where an interior wall or floor system meets the exterior.

This is why an air-sealing product outperforms a higher-rated one that leaves those paths open, and it is why foam's advantage in a real building is larger than the material comparison suggests.

Retrofit walls are a harder problem

In an existing house the cavity is closed. Options are injection foam through drilled holes, taking the interior finish off, or working from outside during a re-side.

A re-side is the moment to do it properly, because the sheathing is exposed and continuous exterior insulation becomes possible. If you are re-siding an Alberta house in the next few years, plan the insulation into it rather than after it.

Wall Spray Foam Insulation Alberta: Common Questions

Can foam be injected into an existing closed wall? Injection systems exist and can work, but they are a different product and process from spray-applied foam, with different coverage certainty. We would rather be straight with you about that than oversell it.

Which is right for my new build - closed-cell, open-cell or flash-and-batt? It depends on cavity depth, target performance, budget and the rest of the assembly. All three are legitimate in Alberta. The wrong answer is choosing without looking at the whole wall.

Does the wall still need poly? That depends entirely on which assembly you use. Closed-cell at sufficient thickness is its own vapour retarder and a second one can trap moisture. Open-cell needs one. This is exactly the detail that has to be designed for our climate zone.

How much difference will I actually feel? The air seal is what people notice - the drafts stop and the rooms even out. The R-value is what shows up on the bill.

Get a wall assembly quoted

Get a free quote with the wall construction, cavity depth and whether this is new build, re-side or interior renovation. See new construction and residential.