The basic concept remains the same installing enclosed ceiling fan in the attic, on the attic floor or in the useful space of the interior ceiling, attracts fresh air through the open windows and pushes the warm air through the attic vents and of the roof. However the central ventilation equipment has evolved considerably. In the past, large and noisy fans were fixed to the ceiling beams so that air was passed through registers on the interior ceiling. Today, the central fans are smaller, quieter and more powerful equipment that drives more air in combination with shutters or automatic shutters to prevent air leakage during the colder months.
The cooling capacity of the enclosed fans is measured in cubic feet per minute (CFM). To find out the size of a particular building, first calculate the volume in cubic feet of the building. Multiply that volume by 30 to 60 air changes per hour (a heating, ventilation and air conditioning professional can help determine the most appropriate figure based on weather and plant), then divide by 60 minutes to know the capacity in cubic feet per minute that housing requires. If the central fan does not come with a watertight sealing cover, consider purchasing or building one. A hermetically sealed hinged door for the fan opening, which is easy to open and close when the unit is in operation, will keep out both cold air in the winter and hot air in the summer.
The best place to install a fan is in a central hallway or near this one. When installing the central fan makes sure there is enough space around the fan in the attic to ensure good air circulation (at least a minimum space of 30 inches from the top of the unit to the beams or roof trusses). Ensure attic ventilation openings are sufficient to draw warm air. If the attic is closed and only ventilated through soffit or ridge vents covered with insulation, you will need to install more ventilation, such as gable vents. It needs almost 1 square foot of net free area for every 750 cubic feet per minute of fan capacity.
Insert a nail through the inner ceiling in the center of the place where the fan will be placed. From the interior of the attic, remove the insulation material and make sure there are no cables or pipes that interfere with the installation. Cut and remove a sheetrock piece to adjust the unit wicket. You may need to frame a standard opening by cutting a beam and installing two beam-sized pieces of wood attached to the adjacent beams. If the beams have a lot of play or rebound, you may need to add a stabilizer in the center of the opening to reduce vibration during operation.