Airtightness limits uncontrolled airflow through the envelope. A designed ventilation system still provides fresh air.
Airtightness and ventilation
Leaks do not provide consistent ventilation; their flow depends on wind and temperature. A sealed envelope allows controlled airflow but does not remove the need for ventilation.
The air barrier
Identify a continuous layer in the drawings, such as plaster or a suitable connected membrane. Insulation itself is not necessarily airtight.
Energy and draughts
Air bypassing the heat exchanger through leaks carries heat without controlled recovery. A local leak near an occupied area can be uncomfortable even at an acceptable room temperature.
Moisture carried by air
Warm moist air can enter cold layers through a leaky connection. This differs from vapour diffusion through materials; checking one mechanism does not check the other.
Continuity
Wall-to-roof, foundation and window connections and service penetrations need particular attention. Specify compatible products, substrate preparation and installation access in advance.
Errors and interim inspection
Unsealed penetrations, dusty substrates and inaccessible joints are often discovered too late. Inspect and test before lining conceals the work.
| Item | Parameter | Check / result |
|---|---|---|
| Plaster | Cracks and junctions | Inspect before finishes |
| Membrane | Laps and punctures | Compatible sealing |
| Penetrations | Gaps | Collars and inspection |
What this means for your project
Assign responsibility for air-barrier continuity across trades. Record the construction stage associated with each test result.
Sources and scope of review
- PHI Passipedia — Airtightness measurements
- PNNL / Building America — Moisture control for residential buildings
Related reading
- Blower Door Test: When, How and Why to Test a Building
- Mechanical Ventilation with Heat Recovery: How It Works