Guide to Your Air Tightness Test

Why Your Building Needs an Air Tightness Test

When it comes to energy efficiency, keeping a building’s air barrier continuous and leak-free is essential. Air tightness testing measures how much air escapes from inside a building to the outside at low pressure. Even small leaks can create cold draughts and dramatically increase energy use.

Why Air Tightness Matters

Up to 50% of a building’s heat can be lost through an unsealed envelope. That means the money you invest in high-performance insulation, premium boilers, or ground-source heat pumps can be wasted if the structure isn’t airtight. A failed air test can also delay handover, adding cost and frustration to any project.

Testing provides a clear air-leakage figure (measured in m³/hr/m²), which is then compared to the limits set by building regulations. This ensures the property meets efficiency standards and gives you a benchmark for improvements.

Building Regulations to Know

Two main UK regulations govern air tightness:

• Part L1A – for new dwellings
• Part L2A – for commercial spaces such as offices and public buildings

Compliance is checked by Building Control and feeds into energy assessments: SAP (domestic) and SBEM (commercial). Both evaluate a building’s carbon footprint, where airtightness plays a major role.

If Your Building Fails the Test

A first-time pass is the goal, but if your property falls short, targeted diagnostics can identify the leaks:

• Commercial Smoke Testing – Pressurising the building while filling it with smoke reveals hidden gaps as smoke escapes. Smaller properties can use handheld “smoke pencils.”
• Thermal Imaging – Infra-red cameras highlight hot and cold spots, showing exactly where air is leaking.

Unlike companies that simply test and walk away, a good testing service will work with you to plan fixes and retest for compliance.

Common Air Leakage Points

Addressing these trouble spots early can prevent failed tests:

• External wall/floor junctions
• Behind fitted kitchen or bathroom units
• Around poorly sealed windows and doors
• Around service penetrations (pipes, cables, vents)
• Through attic hatches or loft doors

Bottom Line

Air tightness testing is more than a regulatory checkbox, it’s key to comfort, lower bills, and a reduced carbon footprint. By planning for airtight construction from the start and working with a proactive testing team, you’ll protect your investment and ensure your building performs as efficiently as possible.

For expert testing or consultancy, visit the Air Pressure Testing website or call 01525 303905.