You are using an outdated browser. Please upgrade your browser to improve your experience
So what is an air test? An air test is the assessment of the total leakage from a building at a set reference pressure of 50 pascals (Pa).
This is achieved through two different types of equipment: a 50Pa fan system, or a 4Pa low-pressure pulse system. Both types of equipment have pros and cons, with most air testers preferring the more tried-and-tested 50Pa ‘blower door’ system due to faster turnaround and track record.
As air tightness is part of building control sign-off, a competent professional must undertake an air test following CIBSE TM23 regulations for any buildings approved after June 2022, and ATTMA TSL1 guidelines for earlier builds. Generally, the building must have all external penetrations finished and installed, and be in its finished format:
• all exterior doors and windows in position, and
• any gas, water or electrical lines/pipework signed off.
The air tester will set up the testing equipment and undertake numerous readings (a minimum of seven) at different reference pressures both above and below the target 50Pa value. This is used to chart a graph from which the reference 50Pa reading is taken – multiple test points give a more accurate final result.
This air leakage result is then compared with a set of building calculations detailing either the total building envelope (all external walls, floors, and ceilings) for Building Regulations or with the total air volume within the building for certain international standards, such as Passivhaus. Click here to find out more about these elements.
Here’s a condensed list of non-dwelling buildings that don’t require an air test:
With the push for Net Zero and improving UK housing stock, from June 2022 air tightness testing became a requirement in all new-build dwellings, and most commercial/non-dwellings. Whenever a new Energy Performance Certificate (EPC) is compiled, this follows a process document called a Standard Assessment Procedure (SAP).
To create an EPC, the SAP compiles a wide range of different data, from floor areas, glazing types, insulation values and wall orientations to estimate the amount of heating, energy efficiency and any additional elements that may need to be considered. One key component of this input data is the designed air permeability of the building, which is an estimation of the air leakage in a structure.
Alongside the improvements to minimum specifications for insulation and glazing levels in buildings – it would be difficult to build a home with single glazing and no insulation – the same applies to air tightness, with an increasing focus on making buildings less draughty and therefore more energy efficient.
We’ve mentioned air tightness multiple times above, but what is it and how can you improve the air tightness of your future build? This blog explains all.