Natural ventilation: Alltwen Community Hospital, Wales
One of four case studies examining the use of natural ventilation in health centres
Alltwen Community Hospital, Porthmadog, Wales, Nightingale Associates
Completion date April 2009
Services engineer Arup
Gross internal floor area 5,224m²
Predicted annual CO2 emissions 22kg/m²
NEAT Very good 65 per cent (at pre-tender stage)
The rural Alltwen Community Hospital provides 30 beds, an outpatient department, minor injuries and radiology unit and mental health services.
The building is designed around an ETFE-roofed winter garden, and light wells in the ward corridors provide natural stack ventilation. Air is pulled from the perimeter rooms into the ward corridor and the winter garden, which has high-level building management system-operated louvres.
After air-flow modelling by the engineers, the initial aspiration for full natural ventilation in the perimeter rooms was modified. Mechanical ventilation is required in winter, when outside temperatures are too cold and would compromise patient comfort. In winter, trickle vents provide background ventilation, which is extracted through exhaust fans in the en-suite bathrooms. Window size was maximized within the wards to create sufficient air flow; all windows have restrictors.
The scheme also includes a biomass boiler, which provides all space and water heating.
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