Airtightness test
Book Airtightness testAirtightness testing is a legal requirement for new dwellings under Part L of the Building Regulations. It assesses the 'leakiness' of a building's fabric, which directly impacts energy efficiency and heating costs.
When do you need an Airtightness test?
Airtightness testing is legally required for most new build dwellings and extensions in the UK, typically performed once the building envelope is complete but before final finishes are applied.
What happens on the day
A qualified engineer will seal obvious intentional openings (like extractor fans) and then use a large fan to depressurise or pressurise the building. This measures the air leakage rate, and a report will be issued.
How to prepare
- Ensure all external doors and windows are installed and closed.
- Seal all internal doors and windows that lead outside.
- Close all trickle vents, extractor fans, and flue dampers.
- Ensure all service penetrations (pipes, cables) are sealed.
How to improve your result
- Pay close attention to sealing around windows, doors, and service penetrations during construction.
- Use continuous insulation and airtightness membranes where appropriate.
- Employ qualified builders experienced in achieving good airtightness levels.
Why it is useful day to day
An airtight home is more energy-efficient, meaning lower heating bills and a more comfortable living environment with fewer draughts and better sound insulation.
Why we ask these questions
We ask about the property type, size, and construction stage to determine the appropriate testing method and estimated time. Details on heating systems help assess overall energy performance targets.