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How to pass your Air Pressure Test first time

News: Wednesday, June 29, 2011

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Andrew Sadler

Project Manager

Hi, I am the project manager here at Sadler Energy, I have experience across the whole spectrum of services...

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Here at Sadler Energy we have tested some pretty good dwellings, it has to be said we have also been to some pretty poor ones too! From our experience we have written some points to consider to help you pass your Air Pressure Test.

Foundation/ground floor

Check that the wall and floor damp-proof course/membrane forms an adequate airtight layer.

Check that any penetrations through the air barrier (e.g. service pipes) have been dressed. Pre- formed collars, sometimes referred to as 'top hats', which seal to the membrane and around the throat of the pipes are effective means of achieving a good airtightness seal.

With timber frame construction, check that the sole plate is sealed to the foundation/floorslab.

Intermediate floors

Joist hangers can limit penetrations through the air barrier.

If joists are to be supported by the wall, check that there is no air leakage into the cavity.

Ensure timber floorsheets/boards are well fitted and sealed at their edges as well as at junctions with perimeter walls.

Check that the ceiling-to-wall joint has been sealed.


Check that the airtightness layer between the wall and ceiling/roof is continuous ceiling below the roof space.

Check that there is a continuous air barrier over the whole ceiling area.

Check that service penetrations (ventilation ducts from extract fans and light fittings) have been properly sealed where they penetrate the air barrier.

Check that loft hatches are airtight and surrounds are sealed where they penetrate the air barrier.

Windows and doors

Specify good quality windows and doors.

Check that the wall-to-frame junction is properly sealed and continuous with the wall's airtightness layer, particularly at sills.

Check that all the windows and doors have an appropriate weatherseal between the opening unit and the frame.

External doors (and letterboxes) should be fitted with draught excluders.

Service penetration

Check for seals at service entry points (pipe and cable routes), e.g. around incoming water pipes, gas pipes, electrical cabling, as well as waste water pipes for sinks, baths, washing machines, dishwashers, etc. Seals should be provided internally and externally.

Where several services penetrate at the same point, there should be sufficient space to fully seal round each of them.

Brick/block masonry construction

Check the quality of construction as the work proceeds. Good mortar joints are required (i.e. no gaps around the blocks or bricks) on both internal and external faces.

Blockwork is unlikely to provide an adequate air barrier on its own. However, the application of wet plastering, parging or the addition of fully-sealed dry lining will create a good air seal.

Parging is an effective method of sealing around joists that penetrate the inner leaf of an external wall.

Check that there is a good seal around all services that penetrate the wall.

Dry lining

Check the plasterboard is continuous (e.g. there are no large holes behind the kitchen units/bath). Ensure that airtightness measures have been incorporated at all edges, particularly at the floor/ceiling junctions and around openings.

Check the plasterboard is correctly detailed at joints, corners, reveals and window sills. Plasterboard should be mounted on ribbons of plaster or adhesive around all the edges (rather than dabs) to prevent air leaking through the porous blockwork behind.

Parging the blockwork prior to applying the plasterboard will improve airtightness.

In timber frame construction, the edges of the boards can be sealed direct to the timber framing.

Wet Plaster

The application of a wet plaster finish can provide an adequate seal to what would otherwise be a leaky brick or blockwork wall.

Check that the wet plaster finish covers the whole surface of the wall or ceiling.

Vapour barrier

Where the vapour barrier is used as an air barrier, check that it is complete, that all joints have been sealed and that the material has not been damaged.

Timber frame construction

In general it is easier to make a timber frame dwelling airtight than other forms of construction. This is partly due to pre-fabricated construction and the use of the impermeable vapour barrier as the air barrier, but also because the plasterboard itself can be sealed to form an air barrier.

Where the vapour barrier is used as the air barrier, care will be needed to avoid it being torn. Any damage to the vapour barrier must be repaired.

If you have any questions regarding this form, or would like some advice and guidance on Air Pressure Testing relating to your development please do not hesitate to contact one of our specialists on 01962 718870 or visit our Air Tightness Testing Page

Why not ask us for a quote?

We have extremely competitive pricing, why not get a free non-commital quote.


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