How Do You Pass an Air Tightness Test?

When planning your build, you should be aware of potential air leakage. All buildings are required to have an air tightness test according to Part L of the building regulations, introduced in 2006. In this blog, you will learn how to ensure your building passes an air tightness test. 

So, how do you pass an air tightness test? You pass an air tightness test by ensuring all openings and appliances are securely sealed and fitted. The building must be fully completed before the test takes place and be clear of any obstructions or trades that will affect the result of the test.

Read on to discover how to avoid failure in your house’s air tightness test and what classifies as a good result.

How Does a House Pass an Air Tightness Test?

Air tightness tests are used to measure the amount of air loss through leaks in a building’s structure. Firstly, make sure that the build is fully completed, including checks before the test commences, to avoid the potential penalties of a rebooking. Every floor of the building should be completed to the expected standard, including any access below ground level and attic. To prepare for the test, we recommend that you read the current rules and regulations

You should also check that all of the following have a snug fit and have been properly sealed:

  • Gaps around appliances, especially where they enter and exit the building
  • Behind and around any fitted units and panels
  • Areas with potential gaps between floors and ceilings, most importantly in suspended floors
  • Around openings such as doors and windows
  • Sockets and light fixtures
  • Any access hatches to above or below ground floor
  • Skirting boards
  • The materials and structure used in the build

How Do You Do an Air Tightness Test?

To perform an air tightness test, an expert air tester from organisations such as ATTMA or IATS will use a huge fan controlled by a computer to blow air throughout the building through an external opening such as a door or window. This same device is then used to check against different pressures, through any cracks and openings in the house. 

What is a good Air Tightness Test Result?

In the UK the Maximum Air Permeability is 10 m3h-1m-2. A good air test result for a new build is between 3 – 5 m3h-1m-2, usually accepted by building control and your SAP assessor. A reading of less than 3 m3h-1m-2, or more than 10 m3h-1m-2 is unlikely to be accepted as extra measures would need to be taken, such as ventilation systems, to ensure the correct air flow through the building.

What Happens if a House Fails an Air Tightness Test?

If a house fails the air tightness test, an assessor can evaluate the building to find all sources of air leakage. After  improvements to sealing fixtures, fittings and openings are made, the air test can be carried out again to see if the building passes.

Common test failures include gaps around appliances in kitchens and bathrooms, chimneys and fireplaces and skirting boards. Failure to meet the standards can result in:

  • Heat energy loss
  • Cold environments for occupants
  • Higher heating bills
  • Reduced energy efficiency and CO2 emissions

How Do You Improve Air Tightness?

Developing a strategy during the building’s design stages to relay to all involved with the build can help with consistency. To increase the rate of success in an air tightness test, the building should be made as secure as possible during the build. This can be achieved through ensuring that thermal bridging details have been followed correctly so that there are no gaps in insulation. However, you must balance an appropriate air flow level to allow for ventilation for the building’s inhabitants.

Air Tightness Tests at RS Energy

At RS Energy we determine the amount and costs of energy required for your build. While we work with you, our SAP assessors will take into consideration air tightness and ventilation during the design stage of your build. 

Request a quote today to learn more about our SAP Calculations.