Ventilation: Installing A Whole-House Fan

There are several effective methods of trying to beat the heat in one’s home. An air conditioner (central, wall or window mount), a swamp cooler, a decorative ceiling paddle fan and a portable table-top fan are among the most popular choices. However, each of these systems will be required to work harder if an attic is not properly ventilated.

Most homes are required by building code to have passive attic ventilation such as eave, gable or ridge vents. Unfortunately, more often than not, passive ventilation is not enough to adequately reduce the 150 plus degree temperatures that hot weather can generate in an attic. This “hot box” effect in the attic acts as a giant radiator, transferring attic heat to living space below. This compounds the cooling problem sending utility bills and tempers soaring.

The first step in keeping your cool involves beefing up passive ventilation. This usually involves increasing the number and type of vents. For example, additional eave vents can be added, a gable vent can be installed where none exists, a ridge vent can be installed and wind driven turbines are a consideration.

Insulation is another primary factor in keeping living space comfortable. Attic insulation should be up to par in terms of thickness and quality. Most climates require a minimum of R-38 insulation in the attic. Many American homes contain less than half of that amount. What’s more, old attic insulation can become compacted which significantly reduces its effectiveness.

Old, compacted insulation should be removed and replaced with new blown-in or batt insulation. Existing insulation which is not compacted and in good condition can be added to by simply adding more material until the desired thickness has been attained.

Aside from passive ventilation and insulation there are “active” forms of ventilation which can have a marked difference on comfort and the utility bill. Unlike passive ventilation, active ventilation systems employ mechanical equipment to exhaust hot air. Two of the most widely used active systems are an attic fan and a whole-house fan.

An attic fan draws hot air out of the attic and discharges it to the exterior. The hot air is displaced by cooler air which is drawn in from vents which are located at the eaves, for example. An attic fan is generally located at one of the highest points on the roof. Where a gable exists, an attic fan can be affixed to the inside face of the gable. In either case, the fan requires and electrical circuit and more than one fan can be installed depending upon the volume of air in the attic.

There are three basic methods to operate an attic fan: a switch, a timer or thermostatically. When a switch is used the fan will operate only when the switch is turned on. A timer will turn the fan on and off at appointed times each day. The one that we like the best has an integral thermostat which will automatically turn the fan on and off at preset temperatures.

Some people confuse an attic fan with a whole-house fan. While they perform much the same purpose they are in fact quite different. A whole-house fan does everything that an attic fan does and then some. The air movement caused by an attic fan is confined strictly to the attic. A whole-house fan, on the other hand, ventilates an entire house, including the attic.

A whole-house fan draws in fresh air through windows and passes it through the attic where it is exhausted through gable and other roof vents. Essentially, you kill two birds with one stone, so to speak. You cool your home and your attic at the same time. You even get the added benefit of fresh air.

The louvered shutter intake system of a whole-house fan is typically installed in the attic floor at a central location of the home such as a hall. Installation is relatively simple. First, check that the attic area where the louvered shutter is to be installed is free of electrical, mechanical or plumbing obstructions.

Use a template supplied by the manufacturer to cut a ceiling opening and remove the wallboard or plaster. Next, cut sections out of the ceiling joist where the fan will fit. Support the cut joists with headers between the joists. Frame the other two sides of the opening by installing blocking between the headers. Build a platform of 1 by 6’s to fit over the perimeter of the opening for the fan to rest on. Complete the job by connecting electrical wiring to the fan and by installing the louvered shutter from below using screws.

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