Air Tightness Testing

Air Tightness Testing shows how airtight a building is. The more airtight a building is the less heat energy can escape. A building’s SAP calculations will normally assume a certain level of air tightness in order to achieve a ‘pass’.

An air test is conducted by temporarily installing a large fan into an external doorway of a dwelling and either blowing air into, or sucking air out of the building. The fan is set to a series of different fan speeds to show how much air can enter or escape the building, thus showing how airtight the building is. The result (q50) is measured in m³/hour/m² surface area, (or n50 for Passivhaus, ACH – Air Changes per Hour).

The maximum q50 allowed in a SAP calculation is 10.0, although a result of 5.0 or less is typically achieved.

Making your Building Airtight

Before we carry out an Air Test we would recommend that you check the following: 

• Under floor ventilator grilles 
• Gaps in and around suspended timber floors 
• Leaky windows and door  
• Gaps around windows 
• Gaps at the ceiling-to-wall joint at the eaves 
• Open chimney 
• Gaps around loft hatches 
• Service penetrations through ceiling  
• Vents penetrating the ceiling/roof 
• Bathroom wall vent or extraction fan 
• Gaps around bathroom waste pipes 
• Kitchen wall vent or extractor fan 
• Gaps around kitchen waste pipes 
• Gaps around floor-to-wall joints (particularly with timber frames) 
• Gaps around electrical fittings in hollow walls 
• All boxing sealed 
• Backs of toilets (particularly wall-hung WCs) 

Also, it is worth noting the guidance re: temporary sealing: 

Can be sealed: 

• Fireplaces/woodburners 
• Extractor fans and passive wall/ceiling vents 
• Trickle vents (2013 regs onwards)

*Air Tightness Testing is sometimes referred to as Air Permeability Testing or Air Pressure Testing.