To carry out an air test we will need access to an empty dwelling that has had the sealant application completed. We will install a large fan on the external door frame, normally the

front door. The windows and other external doors will be closed with all ventilation points

sealed, such as trickle vents from inside the building.

The fan will either depressurise or pressurise the dwelling to a pressure of at least -50pa. We then take readings of the pressurisation levels by our anemometer between the outside and inside of the dwelling. We take ten readings at different pressures, along with other readings such as barometric pressure, wind speed and temperature, together to calculate air leakage.

The results are shown as metres cubed of air lost, per hour, per metre square of building envelope (Floor/wall/roof area).

Under Building Regulations Approved Document L, you will require an air tightness test if you are:

• Building any new build residential dwellings

• Building any new build commercial space

Air tightness testing is not required on:

• Extensions (under 100m2)

• Existing dwellings

• Conversions

Air tightness testing is recommended for anyone doing any building works, or indeed, if anyone owns their own house to undertake an air tightness test. We can provide expert advice on key areas of heat loss, in turn, saving you money on heating bills, while at the same time doing your bit for the environment.

Air Tightness Testing is carried out in the final stages of a build, and once the sealant application has been completed. The following also need to of been completed:

• Walls plastered and decorated.

• Internal and external doors fitted and fully operational.

• Kitchen and bathrooms installed.

• Loft hatches installed and sealed.

• Skirtings, sockets, and light switches are complete.

While we carry out testing, windows and trickle vents will be required to be closed and sanitary waste traps filled with water

The first thing we recommend is ourselves. MDL Seal is an all-in-one company that can carry out sealant application and air tightness testing on the same day. Giving you the peace of mind that with any leaks that occur, can be sealed by one of our professional sealant applicators. All of our specialist air tightness testers that are ATTMA approved within MDL Seal, are qualified mastic applicators first and foremost.

Discounted package rates available. Please speak with a member of our team.

If a test is not passed first time, we will help you out as much as we can within a fair time frame. Any minor issues will usually be rectified by our engineers at the time. Other larger issues that occur, and are small enough to fix at the time, we will wait and re-test the property, doing our best to ensure a pass first time.

Not always, but increasingly that is becoming the case. Sample testing is only allowed if the plots you do test, beat their target score by 2m3.hr/m2. This means, if your design air permeability (DAP) is 5, you can score 3 on the plots you do test, therefore not having to test every plot – however this is still at the discretion of building control. With more and more low target scores, the likelihood of beating it by 2 is less and less likely.