Around 9,000 detainees are held in Dutch penitentiary institutions, managed by the Dienst Justitiële Inrichtingen (DJI). These institutions are mostly old buildings, due for renovations from 2030 onwards. With increasingly warmer summers, heat stress among detainees and staff is growing. Effects of heat stress lead to negative impact on mental, psychological and physical wellbeing . Ultimately, these result in threats for the safety in the institution. With renovations starting years from now, effective measures to reduce heat stress are needed now already.

This study researched the factors that cause heat stress, and potential measures that could reduce this effectively. With a computer simulation that calculated heat flows for a cell in PI Zutphen, these measures are carefully compared to one another. The simulation incorporated technical and human factors, calculating both true temperature as perceived temperature. This way, all heat flows are tracked and show insights on different solution approached to cool down the detainees or the cell.

Reducing incoming solar radiation proves to be the most effective measure to reduce heat stress in cells. Additionally, this study points out that the current ventilation system is lacking behind, causing preventable heat stress. Improved and more frequent maintenance can solve this issue, and is therefore explored and elaborated. Besides these technical aspects, behavioural aspects are explored also. Increasing cleaning behaviour and providing knowledge on dealing with heat can lead to lower heat stress and more autonomy, which in turn betters wellbeing and safety in the PI.

Beyond the findings of this study, the computer simulation shows potential in becoming a valuable decision-making tool for DJI. This simulation can be iterated into a more comprehensive model that is to be used for renovation planning. Also, other indoor spaces and institutions can be simulated with it.

In conclusion, this thesis provides action steps wrapped in a roadmap for DJI to reduce heat stress before renovations. This will lead to improved detainee wellbeing and increased safety in the PI.