Ceiling Fans
Ceiling fans should be operated only when the rooms are occupied. Match the fan size to the room size. Variable speed fans are recommended so that the lowest speed can be used in the heating season to accomplish destratification without causing excessive draft. A rheostat should not be installed on fans unless they are specifically designed for this application, or you may damage the fan motor.
Energy use of ceiling fans
Ceiling fans use about the same amount of energy as a 100-watt light bulb. They permit raising the thermostat setting on an air conditioning system 4 to 6 degrees resulting in a savings of 20 percent on A/C costs.
Selecting a ceiling fan
A good warranty indicates better durability. Fans with metal motor housings may require annual oiling while plastic motor housings do not. However, metal housings may have better warrantees and be worth the added maintenance.
Blade material will not affect performance.
Whole House Fan
Whole house fans are useful when outdoor temperatures are within the comfort range ñ below 82 degrees and with a relative humidity of less than 75%. The key consideration in our region is the typically high humidity which, when introduced into a home, will increase the humidity in the home. This humidity will reduce the cooling effectiveness of daytime mechanical cooling because of the latent cooling load, reducing the net energy savings from using a whole house fan.
Optimum benefits from whole house fans
A high mass interior and minimal moisture-adsorbing materials (fabric furnishings, draperies and carpets) increase benefits. A high mass interior will stabilize temperature swings in any home (see section on Passive Solar Design).
A whole house fan should be insulated above the fan box to prevent heat loss in the winter. There are a variety of methods available to accomplish this, including some whole house fan models that can be purchased with a built-in insulating system.
Windows should be opened in all the rooms that are to be cooled, and the air path to the whole house fan should not be obstructed by closed doors.
When to use a whole house fan
The most effective use of a whole house fan is during periods when the air is cool and dry. In the central Texas area, evening hours of the spring and fall 'swing" months are typically the periods that meet these criteria. In the evening or night, the whole house fan will exhaust the hot air that has built up indoors during the day. High evening humidity levels in central Texas during the summer months make use of a whole house fan during this period undesirable. The introduction of high humidity into a living space may have undesirable consequences, including mold and bacteria growth.
The strategic opening of windows will determine where the cool air enters the home and which rooms are cooled the quickest. Some people also use their whole house fan during the day to create a constant breeze in the home.
Selecting a whole house fan
The fan should be sized to accomplish a minimum of one-half air change per minute in the home. Air outlets in the attic must be large enough to accommodate the fan airflow. (Check manufacturers recommendations).
Use a fan with variable airflow and note that larger fans are generally quieter than smaller fans, particularly at lower speeds.
Use a safety feature that will deactivate the fan during a fire.
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