Air tightness testing or air permeability testing is a mandatory building control requirement and current regulations state a maximum air leakage of 10 m³/ (hr*m²) @ 50 Pa must be achieved.
Air leakage contributes considerably to heat loss from a building and is one of the easiest elements of building energy efficiency to understand as everyone has experienced a cold draught before. As building technologies have developed, particularly PVC windows and doors, these draughts are less likely to be as obvious however as they occur at multiple points the cumulative effect is considerable. Often the majority of air leakage can occur between floors and manifests itself as a strong draft which can be felt at down lighters. . There are many other areas which need attention such as window cills, electrical conduits, waste pipes, extract fans and the junction between the wall and the floor. Timber Frame houses need particular care as there is the potential for air leakage everywhere unlike traditional construction which benefits from a solid internal skin.
As with all areas relating to building energy the earlier we are involved in a project the better as we can advise on how the desired levels of air tightness can be achieved. If we are responsible for your Design SAP we will already know what level of air tightness is required to achieve compliance and can act accordingly.
It is important to remember that all buildings (and their occupants!) need to breathe. Whilst air tight buildings are energy efficient they require ventilation. We would always recommend MVHR (Mechanical Ventilation Heat Recovery) in new build, air tight dwellings. Under current building regulations in England & Wales it is virtually impossible to show compliance without very good air tightness and MVHR. These regulations are expected to be introduced in Northern and Southern Ireland in 2017.
