Wall Insulation, Air Sealing and New Homes in Ontario (2026): Air Sealing Cost, the Blower Door, Effective R-Value, Flash and Batt, ICF, the Air Barrier Checklist and Ventilation

Insulation & Air SealingWalls & Airtightness

Walls and Airtightness: The R-Value With the Studs Counted, the Air Leaks That Beat It, and the Test That Tells You Which Problem You Have

Effective R, not nominal. ACH50, not a feeling. Central Ontario, October 2026.

A wall has two jobs: slow the heat and stop the air. Batts do the first and none of the second; a 2×6 R-22 wall is about R-17 once the studs are counted, and a leaky one is worse than that in a wind. The houses I build are ICF, so the wall is R-24 edge to edge with no studs and no poly, and the blower door comes in under 2 without anyone trying very hard. For a frame house these pages give the arithmetic, the assemblies that fix the bridging, the air sealing priced by the item, the test and its numbers, and the ventilation you owe a house once it is tight.

Compare wall assemblies Air sealing costs The blower door

The numbers

R-17effective, 2×6 with R-22 batts
R-24effective, 6 in. ICF, no studs
$2,400whole-house air sealing package, 2,000 sq ft
$300-450blower door test, standalone

The guides

Air sealing cost in Ontario

The package priced: attic plane, basement rim, windows, per item, the before-and-after test, payback.

Blower door test guide

What it is, what it costs, ACH50 benchmarks for Ontario houses by age, and what the number tells you to fix.

Effective R-value and thermal bridging

Nominal vs effective with the table, why a 2×6 R-22 wall is R-17, and how continuous insulation and ICF fix it.

Flash and batt hybrid walls

Two inches of closed cell plus a batt: the condensation arithmetic, when it is worth it, cost.

Does ICF need extra insulation?

No, and why: R-22 and up, no poly on the wall, the ceiling poly, and where people waste money adding foam to ICF.

New-home air barrier checklist

The air barrier drawn as one continuous line, the details at the rim, windows and ceiling, and the test target.

Can a house be too airtight?

No, it can be under-ventilated: bath fans, the HRV, combustion appliances, backdrafting, what to check after sealing.

Exterior insulation at re-siding

Already on the site: continuous foam or mineral wool outside the studs, the jambs and soffits, the payback.

Four rules for walls

  1. Use the effective number. The heat-loss calculation does, the SB-12 form does, and so should the quote. Effective R.
  2. Draw the air barrier as one line. If your pencil has to lift, there is a leak there. The checklist.
  3. Test before and after. A blower door number is the only receipt air sealing gives you. The test.
  4. A tight house gets a fan. HRV sized to the house, bath fans ducted out, the furnace and water heater checked for backdraft. Too airtight?

Have quotes or plans in hand? Let a builder read them first

For $99, I put your attic, spray foam, basement or air-sealing quotes on one grid, check the area and the existing R-value against your house, name the product and the depth each one actually promised, price the air sealing, baffles, hatch and removal that was left out, check the rebate claim, and tell you which one to sign. For a new build or an addition, $249 turns your plans into a whole-house insulation takeoff, attic, walls, basement, rim and slab, with the SB-12 number each assembly needs and a scope three contractors can price the same way.

Insulation quote review, $99 Insulation takeoff, $249 Check the quotes yourself first