How a Home Holds On to Heat
1On a cold winter night, a family turns on the heat and gathers in the living room. Yet someone sitting near the back door may feel a chilly breeze on their ankles. Where is the cold air coming from, and where is the warm air going? The answers come from a few useful science words.
2Heat always moves from warmer places to cooler places. Scientists call this movement heat transfer. In winter, the air inside a home is warmer than the air outside, so heat keeps escaping through the walls, windows and roof. A home cannot stop heat transfer completely, but it can slow it down.
3The main way to slow it is with insulation. Insulation is material that is put inside walls, floors and attics to keep heat from passing through easily. Much of it is fluffy, like a thick blanket. The fluff traps tiny pockets of air, and air that stays still does not carry heat well.
4Materials that let heat pass through them quickly are called conductors. Most metals, such as iron and copper, are good conductors. That is why a metal spoon left in hot soup soon feels hot. Materials that slow heat down are called insulators. Wood, wool, plastic and still air are all insulators. A wooden spoon in the same soup stays much cooler.
5Even a well-insulated home can lose heat through small gaps around doors and windows. A draft is a stream of cold air that slips in through a gap like this. To stop drafts, families can add weatherstripping. Weatherstripping is a strip of foam or rubber that seals a gap, closing it up tightly so air cannot pass. Many homes also have double-pane windows, which have two layers of glass with a thin layer of air or another gas between them.
6Finally, many homes have a thermostat on the wall. A thermostat senses the temperature of the air in the home. When the room gets cooler than the setting, it switches the heater on. When the room warms up to the setting, it switches the heater off. The same insulation that keeps heat inside in winter also helps keep heat outside in summer.