What is Air Pressure Testing?

An air pressure test measures the amount of uncontrolled air leakage. Air leakage refers to air that leaks through a building unintentionally – for example, through gaps, cracks and holes in the walls.

Too much air leakage can impact the efficiency of a building, which can make it more expensive and less energy-efficient. You can lose up to 40% of heat in a building with improper air tightness.

The result of an air tightness test is expressed as air permeability or leakage rate, typically in m³/h per m²@ 50 Pa. The highest allowed air permeability is 10 m³/h per m²@ 50 Pa. Typically, new residential properties aim for 5 m³/h per m²or lower

What Happens During an Air Pressure Test?

An air pressure test can take around two hours to complete in total. Here’s a step-by-step on what to expect during an air tightness test:

The accredited air tightness testers will prepare the site by sealing intentional openings such as trickle vents and mechanical extracts.
They will then set up the large fan in the doorway.
The fan will create a pressure difference between the interior and exterior of the property
The technicians will take readings at different pressure points.
The airflow required to reach and maintain 50 PA will be calculated and then divided by the building envelope space to define the air leakage data.
The results are gathered in this form (m3/h.m2 @ 50 Pa)

What About After an Air Pressure Test?

You will be given feedback when the test is complete. At UK Overheating, we will give a thorough report – including the test results, issues and observations – and provide you with suggestions to improve if the property does not meet the required standards.

If the building passes – You will receive a certificate of compliance, which is needed for regulatory purposes. This certificate must be submitted to the Building Control Body and provided to your energy assessor. The building can then move on to completion and occupancy.

If the building fails – We will outline the specific areas of air leakage, as well as recommendations on how to fix it. You must then carry out corrective measures – and we will conduct another air pressure test to determine whether the building now meets the required standards.

Overheating in buildings has been highlighted as a key risk for the health and productivity of people and businesses in the UK

It is estimated that there are about 2,000 heat-related deaths each year in England and Wales.

This has led to new regulations to ensure occupants in new residential buildings do not suffer excessive temperatures.

Approved Document O England

Approved Document O (2021 edition – England) was released in December 2021 and came into force for all Building Regulations building notices, full plans applications and initial notices for residential buildings submitted in England from 15 June 2022.

Approved Document O Wales

Approved Document O (2022 edition – Wales) was released in May 2022 and came into force for all Building Regulations building notices, full plans applications and initial notices for residential buildings submitted in Wales from 23 November 2022.

Scottish Building Standard 3.28

Standard 3.28 of the Scottish Building Standards Domestic Technical Handbook (December 2022 edition) was released in June 2022 and came into force for all residential Building Warrant applications submitted in Scotland from 01 February 2023.