Hospital wards and modular construction: Summertime overheating and energy efficiency

The UK National Health Service (NHS) is continually under pressure to provide more bed spaces and to do this within a tight budget. Therefore, NHS Trusts may turn to modular buildings, which promise faster construction and low energy demands helping the NHS meet its stringent energy targets. However, there is growing evidence that thermally lightweight, well insulated and naturally ventilated dwellings are at risk of overheating during warm UK summers. This paper examines the energy demands and internal temperatures in two 16-bed hospital wards built in 2008 at Bradford Royal Infirmary in northern England using modular fast track methods. The two-storey building used ceiling-mounted radiant panels and a mix of natural and mechanical ventilation with heat recovery to condition patients' rooms. Monitoring showed that the annual energy demand was 289 kWh/m2 ±16%, which is below the NHS guidelines for new hospital buildings. It was observed that the criterion given in Department of Health Technical Memorandum HTM03-01 can lead to the incorrect diagnosis of overheating risk in existing buildings. Assessment using other static and adaptive overheating criteria showed that patient rooms and the nurses' station overheated in summer. To maintain patient safety, temporary air conditioning units had to be installed during the warmest weather. It is concluded that thermally lightweight, well insulated, naturally ventilated hospital wards can be low-energy but are at risk of overheating even in relatively cool UK summer conditions and that this needs to be addressed before such buildings can be recommended for wider adoption. •Modular construction with mixed-mode ventilation can produce low energy hospital buildings.•Unshaded, well-insulated and thermally lightweight hospital buildings are inherently at risk of overheating, even in a cool UK summer.•OSummertime overheating is exacerbated by restricted window opening, blind corridors, heat from water pipes, and pre-heat within AHUs.•The criterion in Department of Health Technical Memorandum can incorrectly diagnose the risk of summertime overheating.•Well-designed summertime ventilation and shading is essential if thermally lightweight hospital wards are to be safe and healthy.