How to Reduce Energy Costs
Keeping your energy costs in line
As our energy resources dwindle, costs are rising. Gas and electricity are becoming too scarce, too precious, too expensive to waste. So how do we respond to the challenge? We make the most of what we have-we conserve. By insulating and weatherstripping our homes, we keep them comfortably heated or cooled with less fuel, reducing our heating bills and saving valuable resources. In short, we get more for less.
Insulation and weatherstripping help keep unwanted weather outside. A properly insulated and weatherstripped house is comfortable and energy-efficient the year around. In the winter, the heat remains inside and the cold stays out. And in the hot summer, cool air is captured inside where the outside heat cannot enter.
In addition to saving energy resources and money, insulation and weatherstripping can reclaim areas-even entire rooms that would otherwise be practically useless because of heat gain or loss. In winter, they can eliminate chilling drafts that blow through the basement, sweep across floors, or engulf window and door areas. Insulation and weatherstripping make your house more usable and comfortable by helping to regulate the climate inside.
Where your house leaks heat
When your heating system is in operation, heat flows through the house. Eventually it dissipates and is exchanged for cool air. The speed of this process depends strongly on how complete the barriers are between the warm air inside your house and the cold air outside. In summer, the hot air is outside and the cool air inside, but the principle is the same.
Unless your home was built within the past few years, it probably isn't properly insulated or weatherstripped. The lack of adequate insulation and weatherstripping accounts for excessive heat losses or gains.
In all, about 60 percent escapes through the roof, walls, and floor; this is where insulation can cut heat loss by from one-third to one-half. Approximately one-quarter of the heat loss is through windows and doors, depending upon their size and number. Weatherstripping and storm doors and windows can cut this figure by 50 percent. Another 16 percent of the heat escapes by infiltration through vents, chimneys, and similar openings. Some of this loss is inevitable and in fact necessary. But some can be eliminated if you understand the facts about proper ventilation.
The ratio of heat loss through roof, walls, and floors changes drastically in a one-story house, where less of the house is walls and more is roof and floor. In a typical one-story house, about 28 percent of the heat escapes through the roof. On the average, a one-story house requires about 15 percent more energy to heat than a two-story house of the same size.
How heat moves
Because insulation and weatherstripping are designed to control the movement of heat, let's take a closer look at how heat travels. Heat always moves from warmer to colder areas-it seeks a balance. If the interior of your house is colder than the outside air, the house draws heat in from outdoors. Under the opposite conditions, the house gives off heat. The greater the temperature difference, the faster the heat flows to the colder area.
Heat moves from one place to another in three ways: conduction, radiation, and convection. It travels through house walls by all three methods.
Heat travels through a solid object, or from one solid object to an adjoining one, by creeping through the material from one molecule to another. Heat penetrates building materials in this way. In general, the denser a material is, the more quickly heat moves through it. (Some metals are exceptions to this rule, however.)
Wave motion carries heat in much the same way that it transmits light. By radiation, heat can jump directly from warmer objects to colder ones without warming the air between them. At the surface of the colder object, part of the energy is absorbed; some may be reflected. It is by radiation that the sun's heat warms walls and roofs even on a cool day.
Through large air spaces, molecules of air can transfer heat from warm surfaces to cold ones. Heated air rises. In an enclosed space, heat forms convection currents: air warms and rises, then (as it gives off heat to the surrounding surfaces) it cools and sinks again. When this occurs in spaces between structural framing members in a ceiling or wall, a substantial amount of heat may be transferred and lost. But in small spaces or cavities, where convection currents can't develop, air is a good insulator.
Movement of heat through a wall
Heat travels through a typical wall or roof by all three of these methods. The warm air in a room moves to interior wall surfaces by convection and radiation. Then it travels through the interior wall surface by conduction. It gets from the inner wall surface to the exterior wall surface by all three means-by convection currents through the space between framing members, by radiation from one surface to another, and by conduction through the framing materials. It leaves the exterior wall surface by convection and radiation.