Airtightness in Ireland — Part L 1–3 m³/m²·hr, Passive House ≤0.6, and the Blower Door Test

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.

TL;DR

• Airtightness in Ireland: Part L 2022 allows 1–3 m³/m²·hr at 50 Pa, BER A1 typically 1–2, Passive House ≤0.6.

• Tested with a blower door at completion. Interim test at first-fix (before plastering) catches the cheap fixes.

• Continuous airtightness layer is the key: a membrane on the warm side of the insulation, sealed at all penetrations. Design it in, don't add it later.

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.

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.

Sources

Building Regulations 2023, TGD-L. https://www.gov.ie/