Checking the Air Seal Line to Ensure Air Tightness
Many companies don’t fully understand the importance of the air seal line in regards to air tightness. The air seal line is usually the building envelope but this is not always the case. In many instances buildings may have plant rooms where are heavily vented to outside atmosphere, in these instances the air leakage line will be the internal wall that encapsulates the plant room.
Also, the incorrect sequencing of construction work may weaken the air seal line prior to the air tightness test, such as the late addition of mechanical and electrical pipework & cables just prior to the air test, obviously the M&E should have been installed earlier in the project; however, due to insufficient information i.e. missing details on drawings, the M&E is often added at a later stage, thus requiring additional penetrations through the newly completed building fabric, thus compromising the potential air tightness of the building envelope.. Unfortunately once newly formed penetrations are in the envelope, nobody wants to take ownership for the new penetrations and the resealing of the areas, so the air leakage paths are left to the end of the project, often resulting in air tightness test failures.
In many instances – due to programme constraints) operatives are rushed to install new installations, resulting in much larger access holes than is strictly necessary for the service pipework/cables, this often happens in kitchens, utility rooms, bathrooms, toilets and service cupboards. In these rooms service penetrations are often hid behind Kitchen cupboards, behind toilets, sinks, bath panels and under shower. Other areas are around services in airing and boiler cupboards. Once cupboards and boilers etc. are installed, it makes it almost impossible to seal the air leakage paths – especially if it’s close to the air seal line.
In many cases a lack of understanding by building contractors can lead to multiple air test failures. One common problem is the client putting cosmetic appearance above general airtightness; however, with careful air sealing both can be achieved. Unfortunately, with the airtightness target being halved from the old standard of 10m3/hr/m2 to 5m3/hr/m2 or even as low as 1m3/hr/m2, it is absolutely essential that the all air leakage paths are sealed as soon as the M&E is installed.
In our experience another reasons for air tightness testing failures is down to a general lack of understanding as to where the air seal line within the building. Some of the issues that may need to be addressed to overcome this would include adequate training, quality control and building design.
If you employ APT from the start of the project, we can send out our air tightness checklist to help you prepare for the air testing. If each item is actioned in-line with the checklist then our clients usually pass first time. We also offer a site visit service to make sure that the building is being adequately sealed as works progress, so the air leakage paths can be sealed prior to the air tightness test.