Overheating calculations are a required part of the Planning and Building Regulations in the UK following the introduction of Part O in December 2021, which came fully into effect on 15th June 2022. These calculations are designed to assess the risk of overheating within buildings during the warmer months, ensuring that they provide a comfortable and healthy environment for occupants. Overheating is not just a matter of discomfort; it can lead to serious health issues and negatively impact the energy efficiency of a building, leading to increased cooling demands and higher energy costs.

The overheating calculation process evaluates several key factors, including solar gain, internal heat gains from occupants and appliances, ventilation rates, and the thermal mass of the building. Solar gain refers to the amount of heat a building absorbs from sunlight, which can significantly raise indoor temperatures. Internal heat gains come from everyday activities and the use of electrical devices, while ventilation rates and thermal mass help determine how well a building can manage and dissipate heat.

Depending on the specific characteristics of the building and its intended use, one of two types of calculations may be required: The Simplified Method or Dynamic Thermal Modelling. The Simplified Method is generally quicker and less complex, suitable for certain types of buildings, while Dynamic Thermal Modelling provides a more detailed and nuanced assessment, ideal for buildings with more complex designs or higher risks of overheating.

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