Thermal modelling

Photo by Vistry Partnerships


Some councils now insist that new buildings are future proofed against predicted temperature rises by demonstrating that they can provide a comfortable indoor environment in 30-60 years’ time.

But what do you do if the software thinks there’s an overheating problem in your building?

Changing the windows could be an option, but what if you’ve purchased these already?

Or you could add mechanical ventilation to push air out, but there’s no space.

“It can be challenging, but whatever the problem we’ll help you find a site-specific solution,” says Anthony Dale, senior sustainability consultant at Darren Evans.

A thermal comfort model, or overheating assessment, ensures the indoor environment does not exceed a comfortable limit for the occupants.

Thermal models must confirm that the design of the building is in line with CIBSE Guide A and CIBSE TM:52 or with CIBSE TM:59 for residential developments.

Top tips

  1. There are different types of thermal model, with the impact of climate change becoming increasingly important BREEAM assessments require thermal comfort modelling to gain health and wellbeing credits.The London Plan aims to protect people from the risk of climate change. Many councils make it a planning requirement to guard against the impact of climate change in 30-50 years.It’s also common to  insist that major developments ensure the health and wellbeing of building users through a thermal comfort model.There are different standards for schools, commercial and residential buildings.There may be a perceived risk of overheating for a building, so we can run an assessment to help manage this risk for you.
  2. Bedrooms have specific thermal comfort requirements For residential assessments, there are specific requirements for bedrooms, which need to be a certain temperature overnight. “Consider constructing bedroom windows that can be opened at night. This can be challenging though where security is also a concern such as ground floors” advises Anthony. “If windows have opening restrictions, this can impact the ventilation rate – rooms are less likely to overheat the more natural ventilation they can receive.”
  3. Don’t forget about noise Considering the relationship between overheating and noise is vital. If specific windows need to be kept closed, for example, because a nearby road makes it too noisy to have them open, this impacts on your overheating risk. This needs careful consideration when you’re designing the building.

Watch out for: 

There are no planned changes to thermal modelling requirements at the moment. Many residential buildings are still asked to meet TM52 requirements, however, the appropriate standard for dwellings is TM59. We can help with this.
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Next steps

Whatever the size of your project Anthony and our other CIBSE-accredited low carbon consultants can offer advice and support at every stage of the construction process. To get started we need:
  1. Project overview: geometry, floor plans, sections and elevations, insulation and fabric information as well as window specifications
  2. M&E: how are you heating and cooling the property, what’s the ventilation design?
  3. Usage profiles: some assessments have default data we can or should use, but we might need to know more about how the building will be used. For example, how many people will be in each room and at what times of the day?
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