TM59 Overheating Assessments
Helping You Achieve Compliance Without Compromising Your Design
Whether you’re designing a single self-build home or a large residential development, overheating is now a key consideration in modern building design.
Our TM59 Overheating Assessments help architects, developers and self-builders demonstrate compliance with Part O of the Building Regulations while identifying practical design solutions that minimise the risk of overheating before construction begins.
Why TM59 Matters
As homes become increasingly airtight, better insulated and incorporate larger areas of glazing, the risk of overheating has become a significant challenge.
Without early assessment, overheating issues can result in:
Planning or Building Control delays
Costly redesigns
Reduced occupant comfort
Increased reliance on mechanical cooling
Expensive changes during construction
A TM59 assessment identifies potential issues early, allowing practical adjustments while changes are still straightforward and cost-effective.
Who We Help
Whether you’re designing your first home or managing a large-scale development, we tailor our assessments to suit your project.
Architects
Gain confidence that your design will meet overheating requirements without compromising your architectural vision.
Developers
Reduce project risk, avoid unnecessary delays and keep developments progressing smoothly towards approval.
Self Builders
Receive clear, straightforward guidance to help your home achieve compliance while remaining comfortable all year round.
What is a TM59 Assessment?
A TM59 Overheating Assessment uses dynamic thermal modelling to predict how a home will perform during periods of hot weather.
The assessment considers factors including:
Solar gain
Glazing design
Building orientation
Ventilation strategy
Internal heat gains
Shading
Future weather conditions
Rather than relying on assumptions, TM59 creates a detailed simulation of how the building is expected to behave, allowing informed design decisions before construction begins.
More Than a Pass or Fail
If your initial design doesn’t satisfy TM59 requirements, we don’t simply provide a report explaining why.
We work alongside your design team to identify practical solutions that improve thermal performance while protecting the overall design intent.
This could include reviewing:
Window sizes and locations
Solar control glazing
External shading
Natural ventilation
Cross ventilation strategies
Building orientation
Passive cooling measures
Our objective is simple: achieve compliance with the least disruption to your project.
The Earlier You Assess, The Easier it is
The most successful TM59 assessments happen during the early design stages.
Making small adjustments on a drawing is considerably easier than making significant changes once planning has been approved or construction has started.
Early assessment helps:
Reduce redesign costs
Avoid planning delays
Improve occupant comfort
Maintain design flexibility
Increase confidence before Building Control submission
Several industry guidance documents recommend assessing overheating risk as early as possible so mitigation strategies can be incorporated into the design process.
Practical, Collaborative Advice
We’re not simply producing a report.
We become part of your project team, helping you navigate compliance while protecting the quality of your design.
Our approach focuses on:
Responsive turnaround times
Clear communication
Practical recommendations
Collaborative working
Accurate dynamic thermal modelling
Support from initial design through to compliance
Frequently Asked Questions
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TM59 assessments are commonly required when demonstrating compliance with Part O using the dynamic modelling route, particularly where projects involve larger glazing areas, more complex layouts or where the simplified method isn’t suitable.
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Ideally during the early design stages, before planning or construction, when design changes are easier and more cost-effective.
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Yes. We provide practical recommendations that can improve thermal performance while minimising changes to your design.
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Absolutely. We work on everything from individual self-build homes through to large residential developments.
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Timescales vary depending on the complexity of the project. Contact us with your drawings and we’ll provide an estimated turnaround.
Let’s Make Compliance Straightforward
Whether you’re working on a new home, apartment scheme or residential development, we’re here to help you achieve TM59 compliance with practical advice and responsive support.