Basic Facts About Heat Transfer

Every object gives off energy in the form of waves. These waves, called electromagnetic waves, may be infrared, visible, ultraviolet or radio waves. The color (wavelength) of the waves depends upon the temperature of the object. The sun, being very hot, radiates visible electromagnetic waves which we call light waves. People, plants, furniture, and houses or other objects at temperatures found on the earth's surface emit infrared radiation; the radiation has longer wavelengths than visible light.

An object placed in a room will radiate infrared energy to the room and other things in it. The object also receives infrared radiation from all parts of the room and the other things inside. If the object radiates more heat than it receives, it will cool off; if it receives more than it radiates, the object heats up.

Objects touching one another also transfer heat by conduction. Both conduction and radiation are important to think about when building a house or living in one. We use various types of insulation in houses, the object being to reduce the heat transfer through conduction. Heat transfer by radiation is important when it comes to windows.