Site requirements for a building air leakage test

1. The integrity of the structure must be complete prior to the test. Please see “How can I improve the air tightness of dwellings?” below.
2. Our engineer will need access to an external door (approximate size 2.1m high x 0.9m wide) and an electrical supply within 25 metres of the doorway.
3. All controlled ventilation openings will be sealed with polythene sheet or self-adhesive tape during the test. These include mechanical ventilation fans, window trickle vents and open flues/chimneys.
4. All exterior doors and windows must be kept closed during the pressurisation tests. The actual test (after set up) is usually completed in well under one hour. During this period no personnel should enter or exit the building. It is preferable that the building is unoccupied.

Prior to attending site we shall require the following information

1. Floor plans and section drawings;
2. Design-stage SAP reports for each dwelling to be tested; and
3. Contact details for the site manager.

What is an air leakage test?

An air leakage test is a test to determine the level of uncontrolled air flow through gaps or cracks in the fabric of a building. The result of the air leakage test is expressed as a quantity of air leakage (m³ per hour) per square metre of building envelope.

The general requirement of Approved Document L1A is that each dwelling tested must achieve a maximum air permeability rate of 10m³/h/m². However, in order to comply with the carbon emission target a lower air permeability rate may be required. The required air permeability rate for each dwelling can be found on the design-stage SAP report for that dwelling.

Too much air leakage leads to unnecessary heat loss (and consequently, higher CO₂ emissions) and can lead to discomfort to the occupants through cold draughts.

Do I need an air pressure test?

If you are constructing a dwelling then Approved Document L1A states that, with few exceptions, you must perform an air pressure test. For developments of two or more dwellings an air leakage test should be carried out on the lower of:

1. Three units of each dwelling type; or
2. 50% of all instances of that dwelling type.

For developments where no more than two dwellings are constructed, it may be possible to avoid the need for any pressure testing by using an assumed value of 15m³/h/m² within the DER/TER calculations. Your SAP assessor will be able to confirm if this is the case for your dwelling.

What happens if the dwelling fails the air leakage test?

The majority of dwellings tested achieve a first time pass. However, should your dwelling not achieve a first time pass we shall advise you of all air leakage hot-spots and appropriate remedial work. If it is possible for the remedial work to be carried out at once we shall allow a reasonable amount of time for the works to be complete and then re-test at no extra charge. If it is not practical to carry out the remedial work on that day we will arrange for one of our air test engineers to attend site again on another day once the works are complete.

How can I improve the air tightness of dwellings?

1. Refer to the Communities and Local Government accredited construction details.
2. Seal any gaps where pipes and cables pass through the building envelope.
3. Seal any gaps around windows and doors.
4. Drylining is notoriously susceptible to air leakage. Ensure that the plasterboard is continuous (i.e. there are no holes behind fitted units, sinks/baths, etc). When drylining directly on to an external wall the plasterboard should be mounted on ribbons of plaster or adhesive around all the edges rather than dabs. Ensure the joints between boards are sealed and the plasterboard is correctly detailed at joints, corners, reveals and window sills.
5. Draught strip all windows and doors.
6. Draught strip any loft hatches.
7. Seal holes around light fittings and pull cords in the ceiling. If the light fitting is not airtight then install an airtight box over the light fitting in the ceiling void.
8. Ensure there is a good seal around boiler flue pipes.