Airtightness: the invisible detail that makes all the difference

We often talk about insulation, but a very well-insulated wall loses much of its effectiveness if air passes through it. Airtightness is the ability of the building envelope to stop air from leaking in or out through cracks, junctions and openings.

Why it matters so much

• Comfort: fewer drafts, cold floors and rooms that are hard to heat.

• Energy savings: warm air that leaks out is heating you paid for nothing.

• Structural durability: warm, humid air passing through the walls can condense inside them, causing mould and damaging materials.

• Better air quality: combined with mechanical ventilation, an airtight home lets you control the air you breathe instead of putting up with infiltration.

How is it measured?

With a blower door test: a fan installed in a door depressurizes the house, and we measure how many times per hour the indoor air is replaced at a pressure of 50 pascals (ACH at 50 Pa). The lower the number, the tighter the house. The test also helps find leaks during construction, while they are still easy to fix.

Some benchmarks

• Leaky house: more than 5 ACH at 50 Pa.

• Recent construction: about 3.5 ACH at 50 Pa (order of magnitude).

• Novoclimat, detached house: 1.5 ACH at 50 Pa maximum.

• Passivhaus standard: 0.6 ACH at 50 Pa maximum.

Sources: Novoclimat technical requirements (Government of Québec, 2021); Écohabitation.

It's all in the details

Airtightness doesn't come from a single product: it's a continuous barrier that must be maintained everywhere, at the junctions between walls and roof, around windows and doors, and at electrical and plumbing penetrations. That's why it is planned from the design stage and checked on site, step by step.

What about ventilation?

An airtight home must be well ventilated. An air exchanger (HRV or ERV) renews the air in a controlled way while recovering a good part of the heat. “Build tight, ventilate right”: that's the rule.

Want a comfortable, durable home?