The importance of air tightness testing is often overlooked within the build process. Approved document L1 & L2 suggests that air permeability is the physical property used to measure the airtightness of the building fabric. The test measurement is defined as air leakage rate of m3/hr/m2. The old building regulations stipulated an air leakage rate of 10m3/hr/m2; however, this has now been lowered to an average of 5m3/hr/m2 which is far more difficult to achieve
Wherever air infiltration occurs, there is a corresponding exfiltration somewhere else in the building. During the summer, infiltration can bring humid, outdoor air into buildings. In winter, exfiltration can result in moist indoor air moving into cold wall cavities and may result in condensation and ultimately mould and/or rot, which could result in serious lasting damage to the property.
The ATTMA – Air Tightness Testing and Measurement Association governing body for air tightness testing and the defines ‘air leakage’ as the uncontrolled flow of air through gaps and cracks in the fabric of a building. The general public recognise it as draughts. In most cases the main air leakage paths are:
- Service penetration’s around boilers pipes.
- Service penetration’s around under floor heating.
- Service penetrations in the kitchen and utility room.
- Service penetrations in the toilets, bathroom and en-suite.
- Pipework penetrations behind the radiators.
- Service penetrations in the bathrooms and en-suite.
- Around electrical fuse box.
- Around extract fans.
General Air Leakage Paths
- Gaps between skirting board and floor on each floor level.
- Behind kitchen units.
- Behind Utility Cupboards
- Around poorly fitted trickle vents.
- Around Patio doors.
- Gaps around the stairs.
- Around loft hatch.
- Gaps around the bath panel and the shower tray.
If you employ our services from the start of the project, we will send out our air tightness checklist to help you prepare for the air testing. We also over an air tightness design and site survey service, to ensure the building envelope or the defined air leakage line is being constructed properly, we can then highlight any potential air leakage paths so they can be sealed prior to the air tightness test.