TM59 Calculations

Develop a residential space that stays cool, comfortable and compliant

Minimise overheating risks in new builds and conversions

Overheating poses a significant challenge for architects and developers striving to meet TM59 standards without compromising design intent. Misaligned regulations can force changes that impact both aesthetics and functionality, making compliance feel like a trade-off.

At Energy Digest, we try to make sure your design remains intact while achieving compliance. Our TM59 calculations use advanced thermal comfort assessments and tailored mitigation strategies, such as dynamic shading, optimised glazing, and efficient ventilation. Whether you're developing a new build or retrofitting an existing structure, we help align compliance with your architectural vision.

Why do TM59 calculations matter?

Regulatory
compliance

Detailed assessments ensure your project meets CIBSE TM59 and Part O standards.

Support sustainable
design

TM59 calculations encourage passive cooling strategies to lower energy consumption.

Future-proof
buildings

Address overheating risks proactively, accounting for current and projected climate change impacts.

Our Process

Collect building
information

by compiling architectural plans and environmental data.

Arrange an initial
consultation

to discuss project requirements and intended outcomes.

Conduct detailed overheating risk analysis 

through Dynamic Simulation Modelling.

Optimise your
results 

by reviewing findings and implementing mitigation strategies.

Issue your
TM59 reports 

in comprehensive, regulation-compliant documentation.

Offer ongoing
guidance 

throughout construction for a successful implementation. 

Why choose Energy Digest?

Energy Digest goes beyond standard TM59 compliance, tailoring each assessment to the unique needs of your project.

Using advanced Dynamic Simulation Modelling, we identify overheating risks and provide recommendations to enhance thermal comfort while preserving your design's integrity.

Our TM59 assessments support:

  • Thermal comfort: Mitigating overheating risks with design-specific strategies.
  • Sustainability: Promoting energy-efficient solutions for cooling and ventilation.
  • Future-proofing: Addressing climate resilience to ensure long-term comfort and compliance.

We recognise that designs evolve during development, so we include multiple revisions in every package to adapt to changes seamlessly.

Fast turnaround time

To help you meet your own deadlines, we’ll ensure your TM59 calculations are issued within 7 working days.

Multi-disciplined team

We cover 20+ services in the built environment, with specialists providing high-value calculations and strong advice.

Achievable solutions

Our professionals provide recommendations that are calculated to ensure real world outcomes, resulting in cost-effectiveness and high impact.

Unrivalled support

Our service doesn’t end with the reports. We can provide ongoing support and expertise, from planning to completion.

Speak to our
experts today

FREQUENTLY ASKED QUESTIONS

TM59 Calculations
FAQs

TM59 assessments are recommended for all new residential buildings (via Part O) and major conversions, including high-rise apartments, homes, and repurposed structures with high solar gain or urban density concerns.

TM59 complements Part O but applies to both new builds and conversions, offering more flexibility and detailed guidance for managing overheating risks.

Yes, TM59 often informs adjustments such as shading, window placement, and ventilation strategies to manage overheating while maintaining design integrity.

TM59 is mandatory for new builds (if simplified Part O calculations aren’t compliant) and highly recommended for conversions to ensure thermal comfort.

Yes, voluntary TM59 assessments help developers enhance comfort, sustainability, and energy efficiency, providing long-term benefits and future-proofing buildings against climate change.

Understanding
TM59 criteria

TM59 overheating assessments evaluate residential buildings based on their ventilation type.

Naturally Ventilated Homes: Operative temperatures must not exceed 1°C above the comfort threshold for more than 3% of occupied hours (May–September). Bedroom temperatures (10 pm–7 am) must not exceed 26°C for more than 1% of annual hours.

Mechanically Ventilated Homes: Operative temperatures must stay within 1°C above the comfort threshold for no more than 3% of occupied hours. Bedroom temperatures (10 pm–7 am) must not exceed 26°C for more than 1% of annual hours.

Failing either criterion places the building at risk of overheating.

Still unsure?

We offer free phone call and email support until you’re ready to proceed with us.
Access free support for your project now.

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