What is Air Leakage

Air leakage is the uncontrolled flow of air through gaps and cracks in the fabric of dwellings (sometimes referred to as infiltration, exfiltration or draughts). This is not to be confused with ventilation, the controlled flow of air into and out of the dwelling through purpose-built ventilators that is required for the comfort and safety of the occupants.

• Excess air leakage leads to unnecessary heat loss, discomfort from cold draughts and increased energy costs.
• With more stringent building regulations requiring mandatory pressure tests on all new build dwellings, reducing air leakage, or improving 'air tightness', is an increasingly important issue.
• The aim should be to 'build tight - ventilate right'. Buildings should not be too airtight and it is, however, essential to ensure appropriate ventilation.
• The overall air tightness of the finished dwelling depends heavily on getting the original design and specification right. The designer's role is therefore critical.

Standards for air leakage

Air leakage is quantified as air permeability (q value). This is the rate of leakage expressed in cubic metres per hour per metre of envelope area (m3 /hr / m2) in or out of the dwelling. It is measured at a reference pressure difference of 50 Pascals (Pa) by a fan pressurisation test.

Advantages of airtight dwellings

• Compliance- With 2010 Building regulations
• CO 2 emissions -An airtight dwelling will ensure lower carbon emissions. 
• Space heating -The reduced heat loss will mean that a potentially smaller sized heating system may be able to meet the demand temperature and therefore decrease occupants' energy bills.
• Comfort -Draughts and localised cold spots can cause discomfort. In extreme cases, excessive infiltration may make rooms uncomfortably cold during cooler periods. An airtight dwelling will significantly improve occupants' comfort.
• Interstitial Condensation -An airtight dwelling will reduce the likelihood of interstitial condensation and improve building fabric lifespan.
• Sound -Joints between elements and unwanted gaps in the building fabric are sealed as a part of the air tightness requirements. This reduces sound transmission, both from outside to inside the dwelling and also across party walls between dwellings.

When to test

Flats and maisonettes with warrants from May 2011 and other dwellings with warrants from October 2011 will require to be tested. We can also carry out sample testing on current constructions to help identify any weaknesses in your current building practises.

To find out more, call Tom on 01357 520557