Domestic Air Tightness Testing

Domestic Air Tightness Testing

Domestic Air Tightness Testing

Building for Air Tightness


Building Regulations Compliance

The Building Regulations Approved Document Part L, Volume 1 requires all new build developments to be built with air tightness in mind with a focus on the conservation of fuel and power.


Do I Need an Air Tightness Test?

Air Tightness Testing is mandatory for all new build development but can also be applied to existing buildings as part of an energy assessment, which can reduce the building's energy usage and improve the EPC rating for the building.


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

  • Building any new build residential building(s)


Although not a Building Regulations requirement, air tightness tests can also be carried out on:

  • Conversion projects, material change of use
  • Existing buildings
  • Extensions


Our trained and experienced engineers will guide you through this process and ensure that you have the best possible chance of passing this the first time. If the dwelling is to fail to reach the air tightness test target, our engineers will be able to diagnose where the air leakage areas are.

What is Air Tightness Testing?

Air Tightness Testing is a process of pressurising or depressurising a building, measuring the air flow during the test, and using this data to calculate the air tightness of the building.


This must be undertaken by an accredited and competent person using equipment which is designed for air tightness testing and calibrated for accuracy.


How do I Prepare for the test?

Air tightness testing must be considered at every stage of a build, from design, all the way till hand over.


Incorporating air tightness into the design of a building will massively improve the chances of compliance on the first test. Ensuring that tradesmen who are skilled, follow the design and that at every fix stage, the quality of their work is checked.

General Requirements

  • All plaster work must be finished, and skirting boards fitted
  • All external doors and windows fitted
  • All plug sockets, light fittings and any other fittings finished
  • All loft hatches must be in place
  • 240v electricity must be connected
  • Water must be running


Before we Arrive on Site, we Advise that we are Provided with the Following:

  • Scaled or dimensioned, up-to-date plans with onsite construction.
  • Both plans and cross sections of the property.
  • To accurately work out if you have passed your air pressure test on site, we require the Design Air Permeability (DAP) figure. This figure normally between 3 and 8 is found on the individual SAP calculations for each specific dwelling. To pass your test your results are required to be equal to or below this figure.


An air tightness test can be performed without the information above as our engineers can model the dwelling on-site however this will increase the time required to perform the test. If the DAP is not available before the test, we will not be able to confirm whether the dwelling has passed on-site.


How Can I Maximise the Chance of Passing First Time?

  • All skirting boards should be sealed along the top and the bottom if plasterboard is fitted with dot and dab.
  • Ensure that individual plasterboards have a continuous line of dot and dab around the top, sides and bottom.
  • All sockets and light switches are fitted (Ideally dot and dab around each socket)
  • Ensure any penetration made within a kitchen or bathroom for plumbing and electrical purposes are sealed to ensure no air leakage can come from the gap created.
  • Ensure lights fitted to the ceiling are airtight and will not allow air to be drawn through the light itself.
  • Ensure loft hatches are fitted correctly along with the draught seal.
  • For rooms in the roof - Any cupboard provided that is exposed to the roof space must have a door seal and be correctly fitted to prevent it from opening during the test.
  • Where spotlights are fitted in the ceiling ensure they are sealed units.
  • Ensure that windows and doors are fitted correctly with no air leakage.
  • Ensure all windows and doors have draught seals fitted.
  • Ensure no cracks / gaps between the window / door frame and the opening.
  • Ensure service voids are completely sealed therefore preventing any air leakage.


What Happens After the Test?

Once the test is complete whether your score is a pass or fail, Ashby Energy will provide you with a certificate with your result.


Providing the result passes, this can then be passed on to the SAP assessor and building control to complete any other certificate of the building.


If the dwelling has failed to meet the target requirement it is possible to diagnose and resolve the airtightness issues by using none temporary sealing methods or addressing critical design elements for alteration. We will do our best to help your building gain compliance.

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