What is Air Leakage?
The air-tightness of a building is known as its 'air permeability' or leakage rate. Air leakage can occur through gaps, holes and cracks in the fabric of the building envelope which are not always visible. This air leakage affects the building's performance and a building substantially air tight reduces the amount of fuel needed to heat it. This in turn reduces the CO2 produced and reduces your carbon footprint.
Possible Air Leakage Areas
The areas listed below are common causes of uncontrolled air leakage areas,
- Intermediate Floors- Use joist hangers where possible, if built into the walls seal with a flexible sealant.
- Behind Skirting Boards-seal between floors and walls
- Behind Coving-seal between wall and ceiling
- Boxed in Pipes & Soil Stacks-seal when pipes/soil stacks go out through the ceiling into the roof space
- Behind Bath Panels-seal all services and pipe work that penetrate the envelope of the building
- Kitchen Units-seal all services and pipe work that penetrate the envelope of the building
- All Other Surfaces-pipe work and services that enters the building ensure a good seal
- Badly Installed Trickle Vents-the test only allows for trickle vents to be shut and not sealed
- Windows and Doors-ensure a good seal behind plaster board as well as decorators finishing mastic
- Recess Lights-ensure they are fire check fittings that are fitted correctly
- Loft Hatch-poor quality loft hatches often leak
- Any Remedial Work to Floorboards-make sure any holes in timber floorboards are refitted correctly and sealed
Why test for air leakage?
Ireland
From the 1st July 2008, all new buildings require an air-tightness test.
Northern Ireland / Uk
Part L of the Buildings Regulations requires that all buildings that are not dwellings, and that have a gross floor area greater than 500m2, be subject to a mandatory air permeability test. L2 requires that for domestic dwellings a representative sample of houses (in a development) be tested.
What are the positive affects of Air Leakage control?
- Presents a Unique Selling Point for the developer.
- Fundamentally for the consumer, heating bills will be reduced considerably.
- 47% of the UK's CO2 emissions are from homes, this will drop dramatically.
- Tests relate 'draughty' houses to illness and discomfort for the consumer.
- Reduces noise transfer through the leakage paths
- Helps prevent decline of the building fabric due to interstitial condensation
How does the Test Work
The Leakage of air is measured through a door blower fan system which along with other UKAS calibrated equipment and gives the air permeability. These processes also know as blower door testing. The testing involves connecting a fan, or a number of fans, to a suitable aperture in the building envelope and pressurizing it over a range of pressure differences.. The fan speed is increased in steps up to a maximum and then decreased in steps. Air volume flow rate through the fan (equal to the air leaking through the building envelope) and the pressure difference across the building envelope are recorded at each fan speed. In calculating air permeability, corrections are made for temperature and barometric pressure. Local wind speed should preferably be below 3m s-1.