New-build overheating and Part O: what every UK self-builder should know
If you are building or renovating in 2026, there is a regulation you cannot ignore: Part O. It tackles overheating in new homes — and with UK summers breaking records, designing comfort in from the start is no longer optional.
What is Part O?
Part O of the Building Regulations (in force since June 2022) requires new residential buildings to limit unwanted solar gains in summer and provide an adequate means of removing heat. In plain English: new homes must be designed so they do not overheat — and you have to show how.
Why it matters more every year
Modern airtight, highly-insulated homes are wonderful in winter but can become uncomfortably warm in summer, especially upstairs and in south-facing rooms. With record temperatures now routine, a home that bakes every July is a real liability — for comfort, for sleep, and increasingly for resale.
How a 3-in-1 system future-proofs your build
- Designed in, hidden away. Because the ducts are small and flexible, Custom Comfort is far easier to plan into a new build than traditional ducting — with no bulky external units to clear with planning.
- Active cooling that satisfies the brief. Mechanical cooling and ventilation help you meet overheating requirements with confidence.
- Heat, cool and ventilate together. One system covers winter warmth, summer cooling and the controlled ventilation that airtight homes need.
- Heat-pump ready. It pairs naturally with the low-carbon heat sources new builds increasingly use.
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Does Part O apply to my project?
Part O applies to new residential buildings (and some changes of use). Your architect or building control can confirm how it applies to your specific project.
Does Custom Comfort help meet overheating requirements?
Yes — by providing controlled ventilation and active cooling, it directly addresses the heat-removal side of overheating mitigation. We will design to your project's needs.
Is it easy to fit in a new build?
Very — the slim ducts are simple to plan into the structure during construction, far more easily than conventional ducting.