With RdSAP 10 on the horizon, Domestic Energy Assessors (DEAs) will soon have the option to include air pressure testing results in their assessments. This addition could provide homeowners and assessors with the opportunity to achieve higher and more accurate scores on a property’s Energy Performance Certificate (EPC).

It’s important for DEAs to understand what air pressure testing is, when they can include this information in their assessments, and the various benefits this inclusion can have for homeowners.

What is Air Pressure Testing?

Air pressure testing is the methodology used to identify the amount of air that escapes unintentionally from a building via poorly fitted windows, gaps in skirting boards or other areas.

The methodology quantifies the measured air loss as an “Air Permeability Score”. The higher the score, the more air the building is unintentionally losing, potentially leading to higher energy bills and carbon emissions.

The test standard followed for both compliance and retrofit for air pressure testing is the CIBSE (Chartered Institution of Building Services Engineers) TM23. TM23 addresses the air leakage testing of both domestic and non-domestic (commercial) buildings and recognises two test methods: ‘Blower Door’ and ‘Pulse’.

Air pressure tests may also be referred to as air permeability tests, airtightness tests or air leakage tests.

What are the different types of Air Pressure Testing?

There are two types of air pressure testing that Airtightness testers can choose from. Both methods are acceptable under the TM23 standard and building regulations. The two options include:

Who can carry out Air Pressure Tests?

Air pressure tests can only be carried out by qualified Level 1 or Level 2 air testers, who have undergone the relevant training. It is expected that any qualified professional is part of a certification scheme, such as the Elmhurst Airtightness Scheme (EAS). However, it is not mandatory.

There are currently only two approved certification schemes for air testers in the UK; the Elmhurst Airtightness Scheme (EAS) and the Air Tightness Testing & Measurement Association (ATTMA).

Air Pressure Tests and RdSAP 10:

Expected in early 2025, RdSAP 10 will include the option for DEAs to enter an air pressure test result into their assessments, thereby overriding the default assumption for a property’s air pressure.

Where an air pressure test has been conducted on an existing dwelling, a DEA will be able to override the default value provided within the assessment to give a more accurate representation of the property’s energy performance.

Air pressure testing is not compulsory for RdSAP. However, if a test is available, or if the occupier chooses to undertake a test, the following evidence of the test is required:

• If the airtightness test has been completed by a tester registered with either EAS or ATTMA, a copy of the air test certificate is required.
• If the airtightness has been completed by a tester who is not a member of EAS or ATTMA, a copy of the airtightness report is required as well as evidence of the equipment calibration within the last 12 months for a Blower Door test and within the last 24 months for a Pulse test. This is so an auditor can check the validity of the airtightness test.

Following the assessment, a property’s air permeability score will be shown on the relevant EPC, within the ‘breakdown of a property’s performance’ section. This will match how this information is currently shown on a SAP EPC.

This introduction in RdSAP 10 should enable EPCs to provide a more accurate representation of the property’s conditions and enable homeowners to make more informed decisions about future energy saving enhancements to the property.

Elmhurst’s Thoughts:

Joanne Bailey, Elmhurst’s Existing Dwellings Technical Consultant, comments:

“We are excited to see that Air Pressure Testing is being introduced into RdSAP 10. This additional information will give homeowners and assessors the opportunity to produce a higher and more accurate score on their EPC.

At Elmhurst, we often get queries from homeowners asking why their property’s RdSAP EPC differs from the new build SAP EPC. Although there can be several reasons why this happens, once common reason may be that the air pressure test results are absent. RdSAP currently assumes a score of 15, which is a worst-case scenario result. A very good result would be around the 3 or 4 marks.

Air Pressure Testing in RdSAP 10 is certainly going to be useful for homeowners who wish to maximise their rating and better understand their property.”

Further Resources:

If you would like to understand more about the difference between airtightness testing and background ventilation testing, please read our article: Air Permeability vs Background Ventilation – What’s the difference?