Airtightness Topic Guide BSRIA TG 27/2025
Airtight buildings have reduced levels of air leakage. Air leakage, sometimes known as infiltration or draughts, is the uncontrolled flow of air through gaps and cracks in the fabric of a building.
Airtightness is one of the key components of assessing the performance of buildings. In conjunction with providing suitable ventilation, designing and construction buildings to be reasonably airtight can result in reduced energy use, improved occupant comfort and improved indoor air quality.
This topic guide, published by BSRIA in 2025, explains the basics of airtightness: What is it? Why is it important? In what situations is airtightness testing required and how is it carried out? It is aimed at a general construction industry audience including engineers, site managers, and anyone involved in getting a building to pass its airtightness test. The focus is on regulations and standards that apply in the UK and Republic of Ireland, although the principles of airtightness testing apply all over the world.
Download the full document here
This article appears on the BSRIA publications website as "Airtightness (TG 27/2025)" dated June 2025.
--BSRIA
[edit] Related articles on Designing Buildings
- Accredited construction details ACDs.
- Accredited energy assessor.
- Achieving sustainable futures with thermal imaging.
- Air permeability testing.
- Air tightness in buildings.
- Airtightness of energy efficient buildings.
- BREEAM Testing and inspecting building fabric.
- Building performance.
- Building services compliance with the building regulations.
- Draughts in buildings.
- Effective ventilation in buildings.
- Energy audit.
- Energy Performance Certificates.
- Floor plenum airtightness.
- Indoor air quality.
- Leaks in buildings.
- Let us evolve our buildings from being passive structures to interactive and reactive systems.
- Primary air barrier.
- Simplified Building Energy Model.
- Standalone: The new way forward in non-domestic ventilation.
- Thermal imaging of the building fabric in the net zero world.
- Thermal imaging to improve energy efficiency in building design.
- Thermographic survey.
- The history of non-domestic air tightness testing.
- Weathertight.
Featured articles and news
A case study and a warning to would-be developers
Creating four dwellings... after half a century of doing this job, why, oh why, is it so difficult?
Reform of the fire engineering profession
Fire Engineers Advisory Panel: Authoritative Statement, reactions and next steps.
Restoration and renewal of the Palace of Westminster
A complex project of cultural significance from full decant to EMI, opportunities and a potential a way forward.
Apprenticeships and the responsibility we share
Perspectives from the CIOB President as National Apprentice Week comes to a close.
The first line of defence against rain, wind and snow.
Building Safety recap January, 2026
What we missed at the end of last year, and at the start of this...
National Apprenticeship Week 2026, 9-15 Feb
Shining a light on the positive impacts for businesses, their apprentices and the wider economy alike.
Applications and benefits of acoustic flooring
From commercial to retail.
From solid to sprung and ribbed to raised.
Strengthening industry collaboration in Hong Kong
Hong Kong Institute of Construction and The Chartered Institute of Building sign Memorandum of Understanding.
A detailed description from the experts at Cornish Lime.
IHBC planning for growth with corporate plan development
Grow with the Institute by volunteering and CP25 consultation.
Connecting ambition and action for designers and specifiers.
Electrical skills gap deepens as apprenticeship starts fall despite surging demand says ECA.
Built environment bodies deepen joint action on EDI
B.E.Inclusive initiative agree next phase of joint equity, diversity and inclusion (EDI) action plan.
Recognising culture as key to sustainable economic growth
Creative UK Provocation paper: Culture as Growth Infrastructure.