Free tool
Part L 2026 transition checker
Who runs your contract
Awais Sarwar, MSc — Accredited Energy Assessor
Awais is an accredited domestic and commercial energy assessor and the owner of Team EPC Ltd, which trades as Part L Consultant. He has surveyed and lodged EPCs across flats, houses, HMOs, managed portfolios and commercial premises throughout London and the Home Counties, and is currently studying an MSc in philosophy alongside running the business.
Off the clock: cricket, family time, an MSc in philosophy in progress and finding London's best food.
Awais Sarwar
Founder · Accredited energy assessor
The rule this uses
Part L 2021 can still be used where a building notice, initial notice or full plans application was given before 24 March 2027 and work on that building starts before 24 March 2028
It applies building by building, not scheme by scheme.
Guidance only. Your building control body decides whether a particular building keeps transitional protection, and we will confirm the position in writing before any calculation is run.
Background
Why the dates matter more than the design
Two identical houses can be held to different standards purely because of when they were notified to building control and when they came out of the ground. That is what the transitional arrangement does: it protects buildings already in the system, not schemes or companies.
The practical risk on a phased site is drift. A plot programmed to start in early 2028 that slips a few months moves from Part L 2021 to Part L 2026, and the change is not cosmetic — the 2026 standard brings a new requirement for on-site renewable electricity generation for new dwellings, so a design without panels may no longer stand up.
If any of your plots sit near the line, model both cases at design stage. Knowing what the 2026 version of the house needs is far cheaper than finding out after the foundations are in.
Also useful
The other Part L tools
Design-stage information checklist
Build a tailored list of the drawings, specification and services information a design-stage SAP or SBEM calculation needs for your project type.
Part L 2021 vs 2026 comparison
A side-by-side of the two standards as published: dates, scope and requirements, with a source against every line and nothing stated that we cannot cite.
Extension glazing area check
Enter your extension's floor area, its new glazing and the openings it removes, and see whether it stays inside the 25% allowance or needs a calculation.
Part L fee guide
Pick your project type and scale for the guide fee band we quote from, and what the fee does and does not include. Every job gets a written quote.
