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Ceiling fans

One of the lowest energy use appliances for air movement is the ceiling fan.

While this web site takes the purist view, and provides design guidance to avoid even that energy use by achieving air movement by 'climate response' means;

even this architect in some situations reinforces internal passive air movement with ceiling fan assistance.

However, many general installations make poor use of the ceiling fan capability by poor location and installation; with the result that effectiveness is poor.

The ceiling fan can create:-

- chaotic air movement
- low pressure zone against the ceiling
- undifferentiated air pressure elsewhere,
all of which should be avoided.

Ceiling fans which are large, operating at slow rotation, are more likely to create a definite directional airflow and effective air movement.

Where several fans are installed, independent fans set for complementary updraught and downdraught flows, this can reinforce naturally occurring airflows within the room, creating an effective air movement.

Positioning ceiling fans asymmetrically in the room ceiling layout permits downdraught fans to have adjacent walls as 'duct' surfaces, creating deliberate positive pressure airflow in part of the room.

Opposition to such layouts comes from expectation that the ceiling layout of fans and lights be pleasing to the eye - i.e. symmetrical. But the eye is also pleased where ceiling fans are balanced in layout with pendant or chandelier light fixtures; or on a raked ceiling, where the high set fans are balanced by downlights in the lower ceiling.

There are many more detailed options than just sticking a ceiling fan in the centre of the room because that is where the power supply exists.

Ceiling fans set close to walls, or diagonal to one another, create formal airflow, one down to floor level, and the other replacing air at ceiling level, while operating at low speed.

This assists summer cooling of people at floor level; and in winter enables heat to be distributed from wood or gas fire. This permits the fire and its ventilation to also be set at a lower setting without reducing effective warming of the space.

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