The goal of cooling is comfort. Emphasizing this self-evident notion is necessary because it is too easy to associate cooling with some kind of mechanical system, something you buy and install in your home.
A better way of thinking about cooling is as a list of strategies for reducing heat. Many of them are simple and inexpensive projects that you can do to your home.
The idea behind all of them is that our bodies become overheated in three different ways. First, we experience discomfort when the air temperature around us is too high. Most cooling systems concentrate on reducing this temperature, although it may not be necessary because we may feel overheated for one of the other reasons.
We may feel uncomfortable because the air around us is too still for our body’s cooling system to function, even with temperatures within our comfort range. Conversely, a slight breeze may make us feel comfortable, even if the surrounding air temperature is higher than we would normally like.
The third source of discomfort is hot objects radiating heat directly at us. Some heat sources, like the sun or a stove, are concentrated, but our bodies respond to all the surfaces around us.
When the walls, ceiling, floor and furnishings of a room have absorbed heat and are radiating it back toward us, instead of perceiving it as coming from these sources, we naturally blame the hot weather — even if the air temperature is comfortable.
The strategies for cooling your home that follow are designed to minimize one or more of these sources of discomfort.
Reducing Heat Gain
The sun is the source of direct radiant heat, as well as the cause of high air temperatures.
Shading the windows. Anytime sunlight comes directly through a window, it has a double heating effect: it heats any surface it touches and it warms the air. If you shade the windows from the inside with curtains or drapes, they stop the direct radiant heat but still allow the air trapped behind them to heat up.
Better shading comes from awnings, overhangs, vines, or trees. Awnings and overhangs attached to the house should be louvered or have other venting means to eliminate the hot air that they trap against the house.
You must also plan them with the daily and seasonal changes of the sun in mind. When the sun is high in the sky, little overhang is needed to shade a window. When the sun is lower, such as in the morning and evening and all day during the winter, it shines beneath the overhang.
Make the width of the overhang from ¼ to ½ of the height of the window, depending on the latitude, and position it about 8 inches above the window for each foot of overhang width.
East windows and west windows are difficult to shade with horizontal overhangs because the sun is so low in the morning and afternoon.
Vertical baffles work better. An even better shading device is foliage — either trees, shrubs, or vines. If the winter sunshine is going to be beneficial rather than problematical, use deciduous species of trees and shrubs.
Another way to shade windows is with the use of screening materials. Sun shades are made of film and attach to the outside of the window.
Some are made of cloth-like woven material that you can hang on the outside of doors or windows that you want to open. These shading devices are designed for maximum visibility and minimum heat gain.
Insulating ceilings and roofs. Insulation is more cost effective in cold climates like Michigan, than in hot ones because the temperature difference between indoors and outdoors is greater.
Most areas of the country need insulation for the cold weather and benefit from it during the summer as well.In hot climates it may not be worth installing insulation unless you rely heavily on air-conditioning and need to increase its efficiency.
Eliminating heat sources. Appliances create heat and humidity. If possible, locate washers, clothes dryers, and water heaters in the garage or other areas outside the house.
Otherwise, be sure that the dryer is vented to the outside and that the bathroom and kitchen have exhaust vents.
Increasing Air Movement
Air circulation is not only important for body comfort, but it also draws absorbed heat away from objects and surfaces that might otherwise radiate it to the occupants of the house.
Creating cross-ventilation. If you live where there are natural breezes, you can use them for most of your cooling needs. Open a door or window on opposite walls in every room.
To give cross breezes a boost as they go through the house, open low windows where breezes enter and high windows where they leave.
Another way to enhance air circulation is with an open floor plan. You can’t very well rearrange the walls of an existing home, but for new designs, keep interior walls and partitions to a minimum to maximize cooling benefits.
If the windows are not in line with the prevailing breeze, place fencing or other solid diverters outside the windows to direct the breeze into the house.
Installing a ceiling fan. Large paddle fans are popular in contemporary homes. When operated at low speed, they are efficient and ensure a constant movement of air, around 200 cubic feet per minute.
Installing a high vent. A venting skylight, an openable window near the ceiling, or a special cupola installed on the roof and connected to the living space with a shaft, all effectively exhaust hot household air if the outdoor temperature is cooler than the one indoors.
For these vents to work best, open low windows or vents around the house to draw in cooler air to replace the escaping hot air. If you have a fan, place it at one of the high vents or windows to speed the escape of hot air.
Installing an attic fan. Small fans in the gable or roof that exhaust hot air from the attic do not actually increase air movement in the rest of the house, but they make it easier to cool the house, and they increase the efficiency of fans or other mechanical devices.
Installing a whole-house fan. Large attic fans keep air moving through the house and out through a central hole in the ceiling. Their main purpose is to cool various surfaces and objects in the house, but they can also improve the efficiency of air-conditioning, especially at night when the outside air drawn into the house has cooled down.