What Is Airtightness Testing?
An airtightness test (also called a blower door test) measures how much air leaks in and out of your home through gaps in the building fabric. A large fan is temporarily sealed into an external doorway, which pressurises (or depressurises) the house. Instruments measure the rate of air leakage.
The result is expressed as air changes per hour (ACH) or air permeability (m³/hr/m² at 50 Pa). Lower numbers mean a tighter, more efficient building.
When Is It Required?
- One Stop Shop retrofits: Required as part of the quality assurance process. Pre-works and post-works tests show the improvement.
- New builds: Required under Part L building regulations.
- Individual SEAI grants: Not required for single-measure grants like attic insulation or cavity fill.
- BER assessment: A BER assessor may use a default airtightness value if no test has been done. An actual test result can improve your BER if your home is tighter than the default assumption.
What Results to Expect
| Building Type | Typical Result | Rating |
|---|---|---|
| Old uninsulated house (pre-1980) | 12–20+ m³/hr/m² | Very leaky |
| Average Irish home | 8–12 m³/hr/m² | Leaky |
| Post-retrofit home | 3–7 m³/hr/m² | Good |
| New build (Part L compliant) | ≤5 m³/hr/m² | Good |
| Passive house standard | ≤0.6 ACH | Excellent |
How to Improve Airtightness
Common air leakage points in Irish homes include gaps around windows and doors, junctions between walls and floors, poorly sealed attic hatches, pipe and cable penetrations through walls, open chimneys, and recessed spotlights in ceilings.
Fixing these during a retrofit (with appropriate sealants, tapes, and membranes) is straightforward. The key is addressing them before the airtightness test, not after. Your One Stop Shop contractor should plan airtightness works as part of the retrofit sequence.
A BER is the starting point for most energy upgrades and grant applications. Homerating.ie has been assessing Irish homes since 2009, with fast turnaround in Dublin and nationwide coverage. Book a BER with Homerating.ie →
Frequently Asked Questions
It's required for One Stop Shop deep retrofits and for new builds. It's not required for individual SEAI grants like attic insulation or cavity fill.
A blower door fan is temporarily sealed into an external doorway. It pressurises the house and measures how much air leaks out. The test takes about an hour and is completely non-invasive.
For Irish retrofits, the target is typically 5 m³/hr/m² at 50 Pa or better. Most older homes test at 10–15 before retrofit. A well-executed deep retrofit can achieve 3–5.