Air Leakage Areas


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  • Any boxed in services that lead to ventilated roofs that are not sealed will act like a chimney for air.
  • Poorly installed or manufactured external windows or doors.
  • Services penetrating the external envelope that are not sealed sufficiently, ie expanding foam around pipework in walls or in screeded floors.
  • Stud walls, timbered floors, dot and dab plasterboard all provide a void for air movement if external air can get into them. The air will eventually come out of sockets, light fittings and under skirting etc
  • Joist hangers and good mortar joints help towards minimal wall and floor air leakage. If joist are built into walls then a flexible sealant should be used around it.
  • Kitchen and bathrooms can also suffer air leakage where unsealed service pipes, unfinished walls or floors are hidden behind bath panels, sinks and kitchen units. Air will find its way out around bath panels, kitchen plinths and units, making it very difficult to remedy due to access problems.
  • Poorly made loft hatches that don’t seal well.
  • Ceiling down lighters not sitting flush or without a fire hood can leak small amounts of air, this can have a cumulative effect on the air tightness test results when it comes to multiple down lights.
  • Log burners that are not sealed well into chimneys.


Good building design and construction methods are important in the early stages of the build. Careful thought needs to be given as to how all these elements come together to save any air permeability issues further down the line. Air has the ability to find its way from a ventilated roof, down a stud wall via drilled service holes or gaps which then leads into the ceiling voids, where it comes out of light fittings or radiator pipes that come out of floors. So here in this particular example, the primary cause is air leakage from loft to stud wall and the outcome is air leaking out of downstairs light fitting.

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Air Permeability Testing Solutions - Bowden Lodge, Oldstairs Road, Kingsdown, Kent, CT14 8EH