Airtightness in Ireland — Part L 1–3 m³/m²·hr, Passive House ≤0.6, and the Blower Door Test
On this page
Part L 2022: 1–3 m³/m²·hr at 50 Pa. BER A1: typically 1–2. Passive House: ≤0.6. Tested with a blower door at completion.
Airtightness in Ireland is measured in air changes per hour at 50 Pa (m³/m²·hr) using a blower door test at completion. Part L 2022 allows 1–3 m³/m²·hr; BER A1 typically needs 1–2; Passive House needs ≤0.6. The airtightness layer is a continuous membrane on the warm side of the insulation, sealed at all penetrations (windows, doors, services, electrical sockets). Design it in from the start — adding it later costs 3–5× more. An interim blower door test at first-fix (before plastering) catches the cheap fixes; the full test happens at completion. Most Irish self-builds that fail the airtightness test do so at service penetrations, not at windows or doors.
When this matters most
You're at design stage and need to specify the airtightness target.
When this doesn't apply
The build is finished and the blower door test is done.
Sources
Building Regulations 2023, TGD-L. https://www.gov.ie/
Frequently asked questions
What is the airtightness target for BER A1 in Ireland?
1–2 m³/m²·hr at 50 Pa. Part L 2022 allows 1–3. Passive House requires ≤0.6. Tested with a blower door at completion.
How much does a blower door test cost in Ireland?
€250–€500 for a single test. Interim test at first-fix: €250–€400. Most airtightness contractors do both.
What is the most common airtightness failure in Ireland?
Service penetrations — pipes, cables, sockets that weren't sealed. Windows and doors are usually fine. A continuous airtightness layer with sealed penetrations is the answer.
When this matters most
You're at design stage and need to specify the airtightness target.
When this doesn't apply
The build is finished and the blower door test is done.
Where to go next
Next decision
The next step in your build sequence.
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
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