Many materials reduce the transfer of heat. These materials sometimes differ depending on whether you want to keep heat in or out. Heat transfer causes items to become the same temperature. Heat always moves from a warmer place to a cooler place; as a result, cold items heat up to room temperature while warm items cool down to room temperature. The transfer of heat occurs consistently to make everything the same temperature.

We use all types of insulation every day.

Shiny Surfaces

While reflective surfaces feel extremely hot to the touch when exposed to radiation or sunlight, the metal is actually repelling the radiation rather than transferring it. The shiny surface acts as a barrier to whatever lies beneath the reflection. The metal bounces the radiation back to where it came from instead of letting it through and transferring the heat. In hot places where people cool their homes, roofs are sometimes made of reflective metal, using the principle of reflection to help the cooling process. You can experiment with this theory by placing a shiny, closed tin can outside in the sun. When you retrieve it, the can will be hot to the touch but the inside will remain cool.

Foams and Insulation

Foams and insulation are made of many materials, from perlite to fiber to cellulose. Asbestos was a common form of insulation until scientists discovered the substance's carcinogenic value causing many deaths. Insulation works well for homes and other buildings because it adds a layer between the inside and outside worlds. This layer helps keep a home cool in the summer and warm in the winter. Both sides of insulation work the same, as the product absorbs heat but does not conduct it, trapping it in the substance. Fibers include materials such as cotton from mill waste; perlite, a volcanic mineral often used in foundations; cellulose, which comes from recycled newspaper; and foams made from chlorofluorocarbons. These materials are used to make items such as coolers and coffee cups.


Clothing reduces heat transfer because material is not a good conductor of heat. Because your body tends to be hotter than the outside world, putting cotton, wool and man-made fibers between your skin and the air keeps your own body heat in. The clothing prevents your heat from escaping into the air. It also limits the cool air coming in, but as heat transfers from hot to cold, its purpose centers much more on preventing the warm air from escaping. The clothing merely serves as a protection against the wind.

Clay, Water, Mud

Clay absorbs heat but does not conduct it. It absorbs the sun's radiation, trapping it in the center rather than letting it pass through to the cool house. Builders also use clay to make walls in structures such as adobe huts. Water, mud and dirt do not easily conduct heat. The substances absorb the heat but require so much energy to heat up that the far side of the substances rarely receives any of the radiation. This principle explains why the top of the water in a still pool is almost always warmer than the bottom and why the inside of a cave is always chilly.