Failing an air test can prove very costly. Here’s a comprehensive review of how to pass an air tightness test first time.

A guide to building airtight healthy dwellings

Failing air tightness tests at practical completion can prove very costly. It can cause significant delays in completion, not to mention the additional costs of remedial work and retest fees.

Building airtight buildings doesn’t have to cost more, providing you have an air tightness strategy and implement it throughout the design and construction stages.

The three key factors in building airtight health buildings are:

  1. Design Tight – Develop an air tightness strategy during the early design stages. Communicate it to everyone: from the design team to the project managers, site managers, labourers and then importantly the sub-contractors.
  2. Build Tight – One person must be responsible for carrying out regular airtightness checks to ensure all site operatives are fulfilling their responsibilities to the air barrier.
  3. Ventilate Right – Airtight buildings must have an airtight ventilation strategy so that they can avoid poor air quality, condensation and overheating.

Detailed guide to passing an air test

The following sections provide a detailed breakdown of each of the three key factors mentioned above.

Design Tight

It is essential to develop an air tightness strategy at an early stage and ensure it is communicated throughout the design and construction phases. The following should be considered at the design stage:

Build Tight

All contractors and subcontractors must be made aware of the air tightness strategy and the importance of not breaking the airtight barrier. An air tightness briefing should be included in the site induction. The air tightness champion should regularly perform visual air tightness checks of contractors and subcontractors work at each stage of construction. The following should be done and checked in the construction stages:

Foundations & Ground Floor


Traditional block masonry

  1. All mortar joints in brickwork should be fully filled.
  2. Wet plaster or parging should be used to form an airtight seal to masonry walls. Plaster right to the top and bottom of all internal walls even when skirting and or coving will be fitted.
  3. No gaps should be left around service penetrations through the wall’s blockwork.
  4. All window and door cavities should be sealed using cavity closers.
  5. The external walls should be sealed before internal stud walls are built.

Timber and frame

Floor Joists & Eaves

Ceilings & Roofs

Windows & Doors

Services Penetrations

Check all fire safety regulations and manufacturers’ guidance before sealing all services.

Ventilate right

It is essential to ventilate right when building tight. Too much air leakage leads to draughts and wasted energy however too little airflow causes poor air quality and can cause a condensation risk.

Approved Document F of the Building Regulations gives guidance on how to achieve comfortable ventilation. This is done with Mechanical ventilation, extract fans, trickle vents and other designed openings.

Part F assumes a design air permeability of 3-4 m3/h.m2 therefore if building to below this mechanical ventilation should be provided.

Preparing for an Air Test

Run through our air tightness checklist thoroughly a few days before the air test is booked, allowing for time to complete any required remediation work.

What Next?

By following the steps outlined in this guide and working with qualified professionals, you can significantly increase your chances of passing your air test. A successful air tightness test ensures your building is energy-efficient, comfortable, and healthy for occupants.

For professional air test services, contact us today. We offer a wide range of air tightness testing services for any building type, whether new build or existing. All our testers are ATTMA qualified.

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