ELEMENT:
Ceiling mounted four bladed circulating electric fans
AIM:
Ceiling fans provide a method of cooling occupants of the building when
natural ventilation is not available or in periods where temperatures
and humidity are high.
For small amounts of electrical energy a cooling effect of the occupants
can be achieved. The power consumption is similar to a low wattage light
fitting.
STRATEGY:
Optimise Passive Design
Ceiling fans provide air movement similar to natural ventilation which
provides physiological cooling of the occupants. Appropriate light loose
clothing is needed to achieve the benefits of this form of cooling as
it is related the air movement across the skin. A temperature reduiction
effect of up to 2 deg C can be achieved with this approach.
Fans can be ceiling or floor mounted and deliver air speeds of 1 - 3m/sec.
1m/sec is sufficient for most cooling needs.
Conserve Energy
Ceiling fans can be operated with continuity and with a small impact
on the energy budget. The power consumption is low: 60-100W which is low
when compared to an air conditioner of 1kW.
Indoor Air Quality
More importantly, the building can be left open allowing natural ventilation,
unlike air conditioners or split systems that are more efficient when
the building is sealed. This health consideration of providing a fresh
air flow through the building is important.
DESIGN GUIDANCE:
- Locate the fans to activities, i.e. over beds, adjacent to work areas
- Allow maximum air gap between ceiling and the blades
- Use fans at low velocity with larger paddle size to reduce noise
- Check acoustic output from motor for noise sensitive areas
- Timber blades reduce embodied energy
- Thermostatic control of fan speed can automatically alter the fans
to avoid thermal discomfort (waking in the night when air temperatures
are cooler)
- Reverse cycle fans allow hot air in winter to be drawn from the ceiling
but can cause drafts
- Ceiling fans can be located adjacent to openings to bring cooler outside
air into the building.
REFERENCE:
Hyde, R, Climate Responsive Design. A Study of Buildings in Moderate
and Hot Humid Climates. E and FN Spon, London 2000. p.72.
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