TM59 Part O and Section 3.28 Overheating Assessments

TM59

TM52 & TM59 are standardized approaches to predicting overheating risk for residential and non-residential building designs using dynamic thermal analysis.

Recent evidence has shown that overheating risk is becoming an increasingly important consideration within the construction sector, even in the milder climates we experience in Scotland. With the increase of improved thermal and airtight performance within buildings, overheating is becoming more common and is likely to continue given the predicted increase in climate temperatures.

Overheating can also occur in existing homes, particularly if ventilation systems are inadequate or if the shading design is poor. The impact on health and wellbeing caused by regular overheating can be significant resulting in stress, sleep deprivation, lack of concentration and even premature deaths, especially where occupants are vulnerable.

Many factors can increase the risk of overheating in developments with some characteristics having more of an impact than others. Factors such as location, occupancy behavior, building use, glazing performance, dwelling orientation, shading strategies and ventilation can all have an impact.

When a Dynamic Thermal Assessment is performed for a project, all the above factors are taken into consideration to develop an understanding of the risk of overheating as well as the prevalence of overheating throughout the year, particularly during the summer months.

Using this data, where necessary changes in the design can be made and re-evaluated to reduce or design out the risk of overheating within a development. Future proofing scenarios can also be assessed to adapt to any predicted future scenarios.

Within the building regulations, there are some measures to mitigate overheating, but these requirements are often not sufficient enough to alleviate overheating and therefore an in-depth analysis through Dynamic Thermal Modelling is recommended to provide greater clarity and assurance.

Who will benefit from an overheating assessment?

If you are embarking on a project with significant areas of glazing, limited ventilation, and/or vulnerable occupants e.g. care home residents, it is particularly important to carry out this assessment as overheating is likely to occur.

Developments in busy urban environments will need particular attention as simply opening windows to ventilate homes or offices may not be plausible due to noise or air pollution. There may also be limitations due to security risks (e.g. ground floor flats) or safety (e.g. high rise building).

Schools or offices with multiple occupants and electric equipment should also benefit from overheating assessments as the heat gains from occupants, staff and equipment can increase internal temperatures, creating uncomfortable environments for work or study.