Definition of Insulation

Insulation is a material that has low thermal conductivity (k) and thus lessens the rate of heat transfer. Insulation can be made of a variety of materials, including argon gas (which is sometimes sealed between window panes for insulating purposes) or the typical fiberglass insulation used in the outside walls of homes. Insulation is given a resistivity value (R), which is the depth of the insulation divided by its k value (), using a measure of . However, thermal resistivity (r) is simply the inverse of k (), and uses a measure of (or in English units ). Both R and r are valid measures of the resistivity of insulation.