In this blog you’ll learn:

What is a TM59 Overheating Assessment?

Imagine a computer simulation of your new home, taking into account everything from the size and orientation of windows to the materials used in construction. This is essentially what CIBSE TM59 does. It uses sophisticated dynamic thermal modelling software to analyse how your home will respond to different weather conditions throughout the year, pinpointing any potential risks of overheating.

Compared to simpler methods, TM59 offers a more accurate picture. It considers not just the overall energy efficiency of the building, but also factors like:

Do I Need CIBSE TM59 Overheating Analysis?

All new dwellings require an overheating assessment according to Approved Document O of the Building Regulations. While CIBSE TM59 is one way to achieve this, it is not always mandatory. and Here’s how to decide if it is right for your project:

Benefits of a TM59 Overheating Assessment:

Using CIBSE TM59 for your new build project offers several advantages:

In summary, if your project has any of the complexities mentioned above, or you prioritise a high level of comfort and design certainty, then a TM59 Overheating Assessment could be a suitable method.


A TM59 Overheating Assessment is a valuable tool for ensuring your new home is comfortable, energy-efficient, and compliant with building regulations. While not always mandatory, it offers significant benefits for specific projects. Discussing your project with a sustainability consultant can help you determine if CIBSE TM59 is the right choice for you.

We offer a comprehensive range of overheating calculations, including TM59 Overheating Assessments. Contact us today to discuss your project specifications and work with us to ensure that your new home is cool, comfortable, and future-proof.

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