^ ^^* *^10CN, /^^^^ ^/V//Ô (/o Equipment for Cooling Your Home «mê and Garden Bulletin No. 100 MENT OF AGRICULTURE ^ -■»^êËa: EQUIPMENT FOR COOLING Ü-'^-.-.' YOUR HOME ^^^ It has been a hot, summer day— be several degrees cooler than out- and since early afternoon the in- side, but it can seem warmer if the side of your house has been hot. Now air doesn't move. Also, air move- the sun has gone down, and outside ment increases moisture evapora- the temperature has dropped a little. tion, and moisture evaporation Inside, though, your house remains cools the body, or skin surfaces. just as hot as it was—hotter now A good room fan has large blades, than outside. turns at about 1,000 r.p.m. (it may You open windows, but that have a speed adjustment), operates doesn't help much because the air quietly, and has an oscillating mech- is calm and there is practically no anism. It will cost from about $20 circulation, no exchange of inside for a small table model to $60 for a air for outside air. 7-foot pedestal floor model. (Price If you had some type of air cool- ranges given in this bulletin are ing, you think, it would be better. based on typical 1969 retail prices.) And you decide to do something Attic and window fans exchange about that. You decide to cool your inside air for outside air. You can home mechanically—so it will stay use them for night cooling, or comfortable during the day and be whenever the temperature inside cool at night. your home is greater than the tem- There are four ways, you learn, perature outside. A time switch can to cool your home : be installed in the electrical circuit • With fans. to your fan to cut it oiï automati- • With an evaporative cooler cally at any time you desire. When (cooling with water). you have cooled your house at night, • With an air conditioner. keep the windows and doors closed • With a heat pump. during the next day as long as it is Which way you choose will de- cooler inside than out. pend on how much you are willing You will find that window fans to invest, both initially and in are easier to install than attic fans— operating expenses, and on the cli- mate of your community. Cool With Fans You can buy two types of cooling fans: • Room fans. • Attic and window fans. Room fans stir up the air. The temperature inside your house can no construction is required—but you the rooms by the width. Then mul- will also find that they are usually tiply that by the height. noisier. • If you live in the dotted area of Fans are rated by the amoimt of the map (fig. 1), divide the volume air they move in cubic feet per by 1.5. This will give you a mini- minute (c.f.m.). Fans rated by an mum c.f.m. requirement. If you live Association are more likely to de- in the undotted area, your minimum liver approximately the quantities c.f.m. requirement will be the same of air stated. as the volume you want cooled. For best results, you will need • Pick a -fan that has a c.f.m. rat- the help of an engineer in determin- ing larger than your c.f.m. require- ing the size of attic or window fan ment—a larger rating will allow for needed for your house (some retail slight differences in test procedure firms provide the services of a and efficiency. trained technician). The air inlets If you choose a fan that is driven and outlets, the horsepower of the with pulleys and a belt, rather than fan motor, and the revolutions per one that is driven directly by the minute of the fan blade all should motor, the size of the pulleys can be be taken into consideration. How- varied slightly to adjust the amount ever, you can determine the approxi- of air moved. Models with two- and mate size yourself and probably get three-speed motors are also avail- satisfactory results. able. To detennine the size fan you will Normally, a i/^-horsepower, 36- need— inch attic fan will provide 40 air • Find the volume of the area you changes per hour for the average 3- want to cool. Multiply the length of bedroom house. This is sufficient One change every IK2 minutes One change every minute. Figure 1.—Minimum air changes recommended for fan cooling. Ventilation in the dotte^i area. Such a fan will cost about $100. House Design A larger attic fan is required in the undotted area—a l^- or i/^- Good design and construction are horsepower, 42-inch fan that will as necessary to keeping your house normally provide 60 air changes per cool in the summer as they are to hour for the average 3-bedroom keeping it warm in the winter. The house. It will cost about $120. house should be tightly constructed Window fans are usually smaller. and well insulated. In the summer, They range in size from 20 to 30 the windows should be shaded from inches. The 20-inch size is the most the direct rays of the sun. popular. It will generally provide A more compreliensive discussion about 15 to 20 air changes per hour of house design, insulation, and for the average 3-bedroom house. cooling equipment appears in Twenty-inch window fans cost from USDA Agriculture Handbook 241, $25 up. "Farmhouse Design and Equipment When cooling with a fan, you for Summer Comfort." This pub- should close off any portion of the lication is available from the Super- house that you do not wish to cool ; intendent of Documents, U.S. otherwise, the fan will not provide Government Printing Office, Wash- the proper number of air changes ington, D.C. 20402, at 15 cents per per unit time. copy. You can also remove accumulated attic heat during the day with an attic fan. Often an attic is 25° or Cooling with fans has some dis- more hotter than outside ; even if the advantages. Dust and pollen are ceiling of your house is insulated, likely to be drawn into your home. this additional heat will warm your Fans are noisy. The cost of a good house. attic fan plus installation may be When you remove attic heat with as much as a room air conditioner. an attic fan during the day, close the While the attic fan may cool the attic off from the rest of your house. entire house in some areas at night, Otherwise the fan will draw hot, it may not help much during the day outside air into your house. because of high outside air temper- Suppose you decide to cool your atures. And remember, a fan will home with an evaporative cooler cool your house to only approxi- (cooling with water) or air condi- mately the temperature of the out- tioning, but wish to ventilate the side air. On the other hand, the room attic anyway. A fan—smaller than air conditioner will usually cool the usual size attic fan—will do only one or two rooms, but it wUl that ; it should be capable of chang- cool both day and night. ing the air in the attic at least once per minute, and should operate con- Cool With Water tinuously when the temperature in the attic exceeds 110°. It may be con- In Dry Climates trolled by thermostat, time clock, or You will find that the most com- manual switch. Such a fan with mon and effective method of cooling thermostat and automatic gable with water is the water-evaporation shutter will cost about $60. method. An air velocity of 150 feet per minute through the excelsior pro- vides maximum cooling. Slightly higher velocities keep the circu- WM lated air from becoming saturated. Twenty to 40 house-air changes per hour are necessary. Water-evaporation cooling re- quires 5 to 10 gallons of water per hour to cool an average-size house. Installation and operation costs for a water-evaporation cooling Cooling by water evaporation is unit that is large enough to cool an satisfactory only when the humidity average-size house will depend on is low. It is used extensively in hot, your locality. A single-room unit dry climates. Figure 2 shows the costs from $30 up. areas of the United States where water-evaporation cooling is satis- " ' Cool With an factory. Air Conditioner Water is sprayed on excelsior (or some other good water-absorptive Is air conditioning the answer to material). A fan then draws air cooling your house? Certainly it is through the excelsior. The water in the best way to keep your house at the excelsior evaporates and cools a contant, cool temperature. But it the air ; the cooled air, in turn, cools is also more expensive than other your home. methods of cooling. Figure 2.—Shaded areas indicate where water-evaporation cooling is effective. whole house. A single, large room unit will be less expensive, but it will not cool your home evenly. A central air-conditioning system might be a better buy. Central air-conditioning systems are generally more efficient than room air conditioners. They also seem less noisy because they are lo- cated out of the living area. Central air-conditioning sys- There are two types of air con- tems can be separate systems with ditioners— their own ducts, or they can be com- • Room units. „ bined with forced-air heating • Central-system units.