Can Insulation Save Energy?

An insulator is a substance that partly blocks or slows the flow of heat through it. Styrofoam is a lightweight plastic used in drinking cups. Styrofoam is a good insulator. A cooler or ice chest that is made of Styrofoam or some other insulator tends to block the flow of heat through it.

Heat flows into buildings during warm summer months and from buildings during cold winter months. Energy must be used to cool buildings in the summer and heat them in the winter. Since insulation can slow the flow of heat, the use of insulation in buildings can save energy.

Some common home and building insulation materials include Styrofoam, polyurethane foam, and fiberglass. These materials are all good insulators, which means that they are poor conductors of heat. Placing these insulating materials on attic floors or in building walls tends to trap heat inside during the cold winter and keep heat out during the hot summer.

Plastic foams filled with trapped gas tend to block heat flow. The chemicals used to make polyurethane foam can be sprayed directly into the spaces between walls. These chemicals produce carbon dioxide gas and polyurethane plastic. The gas tends to spread the polymer apart so the weight is mostly plastic but the volume is mostly trapped gas. Polyurethane also is used to insulate refrigerators, refrigerated trucks, pipes, and building walls.

Fiberglass insulation is frequently used in attic floors to insulate homes. Also, fiberglass insulation is used to insulate the Trans-Alaska pipeline. This pipe carries oil 800 miles from Prudhoe Bay in northern Alaska to Valdez in southern Alaska. The crude oil that travels through this pipe is easier to pump if it is hot. An insulated pipeline requires less energy to keep the oil hot.

Energy conservation becomes more and more important as energy costs rise. A great deal of energy is used to cool buildings in summer and heat buildings in winter. Less energy will be needed if buildings are well insulated and energy is not wasted.
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Materials

• Two large, plastic cups
• Small, insulated ice chest or cooler (Styrofoam or plastic)
• Ice
• Watch or clock

Procedure

Completely fill each plastic cup with ice. Set one plastic cup out in the room. Set the other plastic cup of ice inside the small ice chest or cooler. Close the lid of the ice chest and leave both cups undisturbed.

Observe the cup of ice left out in the room once every hour. When all the ice has changed to water in the cup left out in the room, open the smaller cooler and observe the cup of ice inside. Continue to check on the cup of ice in the cooler about once an hour and see how long it takes to melt.

Observations

How long does it take for the cup of ice in the room to melt and change to water? When all the ice has melted in the cup in the room, is there still ice in the cup in the ice chest? How long does it take for the ice in the cooler to melt?

Discussion

You should find that the ice in the room melts faster than the ice inside the ice chest. When the ice in the room has all melted and only water remains, the cup inside the insulated cooler may still be mostly ice. Even though both cups were filled with the same amount of ice, they did not melt at the same time.

The temperature in the room is much warmer than the temperature of the cold ice. Since heat always flows from a higher temperature to a lower temperature, the heat in the room flows or moves into the ice and causes it to melt.

Other Things to Try

Repeat this experiment with a larger amount of ice, and you may see a greater difference between insulated and uninsulated containers. Try filling a bucket and an ice chest with equal amounts of ice, and set both containers outside on a warm day. How long does it take the ice in the bucket to melt? How long does it take the ice in the ice chest to melt?

You can reverse the experiment by comparing the flow of heat from the inside of a cup to colder surroundings. Use hot water from a sink faucet to partially fill a Styrofoam cup and a glass cup. Place the Styrofoam cup inside two other Styrofoam cups and cover the top with several layers of aluminum foil. Next place the Styrofoam cups and the glass cup inside the refrigerator and compare how long it takes for the water to cool.

Fill a thermos bottle with hot water. Wait about four hours and check the temperature of the water. Continue to check the temperature about every two hours to find out how long the thermos bottle can keep the water warm. A thermos bottle has glass walls with a vacuum between them and silvered surfaces to reflect heat. The vacuum in a thermos makes an excellent insulator because there are few gas molecules to transfer heat.
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