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Roof Design

Air Leakage

Air leakage (also referred to as air infiltration) causes a loss of heat from within a building, with roofs, walls and floors accounting for approximately 30% of total heat loss of a building.

The resulting energy loss increased loads placed on the heating and/or cooling systems due to the constant, uncontrolled, flow of air through the building fabric.

As part of the Government’s commitment to reduce CO2 emissions requirements for the air tightness of buildings were introduced into the Building Regulations for England & Wales in 2003.  Regulated through the Approved Documents Part L ‘Conservation of Heat & Power’, the targets and requirements for testing have been steadily increased in each revision since.

Current requirement exists in three of the four Part L Approved Documents:

1.  Part L1A: new dwellings

2.  Part L2A: new non-dwellings

3. Part L2B: large extensions to non-dwellings.


Air tightness testing is a means to quantify the extent to which buildings ‘leak’ air through their envelopes (for example perimeter walls, roof and floor slab).   For further information on air leakage testing go to The Air Tightness Testing and Measurement Association (ATTMA) website www.attma.org.

Radmat’s products and systems can contribute to achieving high levels of air leakage resistance at roof detailing and penetrations.