Healthcare Technical Memorandum 03-01 (HTM 03-01) provides a host of guidance concerning the ventilation of healthcare premises.
In respect of overheating, the guide requires that:
‘Calculations and thermal modelling should be undertaken to see whether, during the summertime, internal temperatures in patient areas will exceed 28oC dry bulb for more than 50 hours per year. It can generally be assumed that for a naturally ventilated building, the internal temperature will be approximately 3 K above the external shade temperature. For a building with simple mechanical ventilation, the internal temperature can never be less than the external shade temperature and will invariably be higher. The relationship between preferred indoor temperatures and mean outside temperature is discussed in CIBSE’s Guide A.’
In a similar fashion to CIBSE Guide A overheating guidance, the HTM 03-01 guidance is a minimum requirement which may not satisfy all occupants –especially if accustomed to an air conditioned environment. A more stringent overheating definition such as CIBSE TM52 may need to be considered in addition to HTM03-01 if greater levels of thermal comfort are deemed necessary.