Part O Overheating Calculations aim to mitigate the growing threat of overheating faced by dwellings in the United Kingdom – a challenge exacerbated by the effects of climate change. This issue has profound implications for the well-being and health of inhabitants.

Part O of the Building Regulations took effect in June 2022, with the intention to limit solar gain and provide means to remove excess heat from indoor environments.

For more complex projects or those seeking a more in-depth analysis we recommend TM59 assessments. TM59 is a dynamic thermal modelling method that provides a comprehensive evaluation of overheating risk.

Approved document Part O 2021 mandates that rooms in a dwelling are evaluated in isolation instead of the previously used dwelling average.

Anyone building a house, planning an extension, or converting their home needs to check both the design and materials used aren’t going to cause energy efficiency problems for the property.

Our expert team can provide advice on building regulations and quick turnaround quotes for all compliance calculations.

Our expert sustainability consultants are a team of experienced, friendly, and knowledgeable experts well-versed in building compliance. Get in touch today for a free consultation or competitive quote.

Why work with us?


Our sustainability consultants have extensive experience in meeting regulatory requirements, yet work hard to go beyond mere compliance with the building regulations.

We pride ourselves on delivering decarbonisation advice to help our clients build lower carbon, energy-efficient properties.


We reduce the amount of assumed data in each calculation to the bare minimum, meaning that our overglazing calculations are as accurate as possible.

Conversations with clients are key to this process and our work improves each time we work on a new project, thanks to the collaborative approach we adopt with our clients.


Our office-based staff work hard to book all appointments as quickly as the delivery schedule allows.

We work on a two-week schedule, with the vast majority of overheating calculations being delivered well within that window.


Our rate card prices for all services are reviewed regularly, so we’re confident that you won’t find a better service for a better price anywhere else. If you think you’ve found one, we’ll either beat or match it.


Navigating the complexity of energy efficiency, decarbonisation, and building regulation updates isn’t easy.

We’ve worked hard to explain a range of topics related to building compliance in plain English to help non-experts get the information they need.

Who We Work With

Related Content

Talk to us about Part O Overheating Calculations

Drop files here or
Accepted file types: pdf, jpg, png, dwg, xlsx, Max. file size: 20 MB.
    PDF files are preferred.
    This field is for validation purposes and should be left unchanged.