A powered attic ventilator, or attic fan, is a ventilation fan which regulates the heat level of a building's

attic An attic (sometimes referred to as a ''loft'') is a space found directly below the pitched roof of a house or other building; an attic may also be called a ''sky parlor'' or a garret. Because attics fill the space between the ceiling of the ...

by exhausting hot air. A

thermostat A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint (control system), setpoint. Thermostats are used i ...

is used to automatically turn the fan off and on, while sometimes a manual switch is used. An attic fan can be

gable A gable is the generally triangular portion of a wall between the edges of intersecting roof pitches. The shape of the gable and how it is detailed depends on the structural system used, which reflects climate, material availability, and aest ...

mounted or

roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of t ...

mounted. Additional vents are required to draw in the fresh air as the hot air is exhausted. Attic fans are typically used in warmer months, when temperatures in an

can exceed . A fan may be installed in an attic for the different purpose of cooling a whole house, venting hot air out via the attic; such fans are often called whole-house fans. Roof Turbine Ventilator

Mechanical attic ventilation fans may be powered in a variety of different ways. Most attic ventilators fitted to homes are powered off mains electricity. A trend towards solar-powered attic ventilators is observable in the interest of conserving electricity and lowering monthly utility bills. Wind-powered roof turbines, often colloquially referred to as "whirly-birds", are also used to ventilate attics and other confined spaces.

Wiring methods

Attic fans may be wired in several different ways. Usually, the fan is hardwired directly into an

electric circuit An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, ...

, and is controlled by a thermostat most commonly ranging from to . It may also be hardwired but controlled by a

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

. Another popular method is to have the fan plugged into an

electric socket AC power plugs and sockets connect electric equipment to the alternating current (AC) mains electricity power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and electric current, current ...

mounted nearby. An environmentally friendly method is to wire a specialized fan to a roof-mounted

solar panel A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...

Grounding/earthing

Because an attic fan is made of

metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...

, and is also subject to

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...

strikes if mounted on a

, grounding is extremely important. On some attic fans, grounding is achieved through a

screw A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to ...

mounted on the thermostat box of the attic fan. The grounding

wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is co ...

is attached to the box via the screw and thereby grounds the external metal components. Most modern attic fans have this as well as a grounding wire connected directly to the

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

, thereby ensuring all parts are grounded.

Controversy

Though every situation is different, there is some controversy about the effectiveness of attic fans. It has been theorized that in some cases the negative pressure that an attic fan produces in the attic can cause conditioned air from living spaces to be pulled into the attic through cracks and lighting fixtures. This loss of conditioned air can negate the energy conservation gains that might be expected from forced cooling of the attic with a fan.

Fire danger

In the possible event of a fire, an operating attic fan could, in theory, spread the flames because of the air movement. To reduce the danger, louvered vents that allow air to pass through can incorporate fusible links so that fire will melt the links in which case the vent will automatically close. In addition, an automatic cutoff switch can be set up to turn off power to the fan if it detects a temperature above a preset limit.

References

{{Home appliances Ventilation fans Cooling technology Home appliances