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Why Air Leakage Test?
We commonly are asked questions about the process of air leakage testing and what it means for clients and contractors. Here we set down some of the procedures and hopefully dispel a few myths.
From 1st April 2006 all buildings that are not dwellings, and that have a gross floor area greater than 500m2, require a mandatory test for air permeability.
Dwellings are also now required to be tested, but, only a sample number of each type of  dwelling being constructed need be tested.
This test has to be carried out to a prescribed standard. This standard is known as CIBSE TM23 and also is generally compliant with EN 13829:200 method B. This is part of the revisions to Part L of the buildings regulations L1A, L1B, L2A and L2B.
The term gross floor area is determined by the ground floor area, (the buildings footprint on the ground) and any additional floors.
Air Permeability means how good a buildings envelope is to resist the inward or outward movement of air.
What we do.
To test for air permeability or air leakage, we simply attach an electrically driven axial flow fan or a door mounted blower unit fan to a suitable opening in the buildings envelope. This is normally a personnel door. We set up various pressure testing and temperature recording equipment, start the fan, and pressurise the building.
This does not involve massive pressures, so visions of roof sheets popping off and windows and doors being blown out are completely unfounded. The amount of pressure we have to put into a building is a maximum of 55 to 60 Pascals (Pa).
What is a Pascal?
This is a unit of pressure. However being metric, not many know what it is. In real money, it might be more familiar to say 1 PSI= 7000 Pa. So as you can see 50Pa is not a lot. Atmospheric pressure is about 100,000 Pascals.
What we do need however is lots of air. This is why we use axial flow fans capable of giving up to 30 cu m of air per minute. We accurately measure the volume of air leaking out of the building envelope. This is expressed as cubic metres of air leaking out in one hour for every square metre of building envelope area (cu m/hr/sq m).
The building, for test purposes, is the total area of ground floor, walls and roof. Or put another way, all parts of the building that have a boundary with outside.
At present buildings have to achieve an air permeability figure better than 10 cu m/hr/sq m @ 50Pa. This can be expressed as a figure from 1 to 10 where 1 is very good and 10 is a borderline pass. Anything above this would fail.
How efficient are buildings at the moment? In our experience, most modern buildings already fall within the required range. Many would achieve this with only a little work. A typical value of a pre April 1 2002 building is in the region of 15cu m3/hr/m2 @ 50Pa. Earlier buildings might be as bad as 50+ m3/hr/m2 @ 50Pa.
To design a building to comply is not difficult. Common sense detailing at eaves, verges, around windows/doors and other junctions is all that is required to effectively block all gaps. Most buildings fail because of poor workmanship and supervision on site rather than design faults.
If you can feel a draught on the inside, or see daylight, you have an air leakage point.
What if our building fails the test?
We will know very soon during the test if a building has failed or passed. If it has failed the areas of leakage need to be found. We can do this with a smoke test or by feeling for draughts. We also provide thermal imaging to identify areas of heat loss.
Armed with these results, a contractor can put into operation remedial works prior to re-testing.
What can I seal before the test?
Once you have ordered an air leakage test from us, we will give you a full list of what you can and can't seal up, what has to be open and closed, and what you may need to remove before we carry out the test. This preparation must be undertaken prior to our arrival. We would also expect a representative of the contractor to be on site during the test to attend to any areas we deem to still be unsuitably prepared.
We can offer friendly help and advice to help you build an efficient airtight building. Our experience is drawn from the construction and engineering industries.
Specific details for each building element are freely available from all the major building component manufacturers. It is advisable to study these carefully and implement their requirements.
Do all buildings need an air leakage test?
From April 1st 2006 all buildings other than dwellings that have a gross floor area greater than 500m2.
Some buildings, say over 60,000m2, at the discretion of the Building Control or ODPM, only require having an audited quality management procedure to show that they meet robust details. This would need to be agreed at an early stage in the development and an air tightness standard of no less than 5m3/hr/m2 should be the design criteria.
Conclusions...
From all of the above information you can see that in order to save life time heating costs and to reduce CO2 emissions from fossil fuel being burnt to heat or chill your building, it is very important to pay attention to the build quality during construction. The thickness of insulation and design details all play a significant part in keeping your eventual costs down. It makes sense therefore to use a reputable company who has the experience and accurate air leakage test measuring equipment, to carry out the works to the required standards.
For this look no further than
AIR LEAKAGE TESTING LTD.
For an uncomplicated and cost effective test and report service.
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