• You can install attic fans directly into the roof.attic window image by green308 from Fotolia.com
  
  Attic fans, also called whole house fans, are electric or solar-powered fans that circulate air within an attic to cool a home. Attic fans are installed into the roof or on the side of the home in the gable. Consider a number of factors before implementing an attic fan in your home.
  
  

Energy Use

• Attic fans typically use less energy than an air conditioner. Models that use solar power are extremely energy efficient as they use the sun's energy to operate. An attic fan that circulates enough air for the space of your attic can quickly cool the space while using significantly less energy than an air conditioning unit.
  
  

Humidity

• When outside air is humid, the attic fan introduces humid air into the home as well. Humid air in the home can feel warm, even though the fan circulates it. In very humid climates, an attic fan may not produce a noticeable cooling effect.
  
  

Pollutants

• Since the attic fan introduces air from outdoors, pollutants easily enter the home. Pollen, dust and smoke can enter the home and exacerbate allergies for homeowners. Attic fans necessitate open windows or additional venting while running, as the fan can draw in carbon monoxide fumes from other appliances, so there must be additional ventilation while running.
  
  

Solar Models

• Solar attic fans have the advantage of energy efficiency; however, since they operate using energy from the sun, they only work while the sun is gives direct light. In cloudy weather and at night, the attic fan will not run. While the fan doesn't run, heat builds up, which can negate the cooling effect.
  
  

Noise

• Some models, particularly older model attic fans, are noisy to operate. Select a model that runs quietly to avoid this disadvantage.
  
  

Cooling

• Attic fans, when used in the correct size for the amount of space in your attic, can circulate a large amount of air very quickly, resulting in a quickly reduced temperature. In moderate or cool climates with low humidity, an attic fan makes a house cool and comfortable. In humid or very hot climates, an attic fan may not produce enough cooling effect to make the home comfortable.
  
  

Installation

• Installation is sometimes difficult if you must cut the fan into the roof or gables. Often the fan requires a circuit solely for the fan, so an electrician is often necessary to complete the installation. Also, you must carefully repair and insulate the area around the fan so to create a tight seal to reduce the loss of cool air.