thermal insulation

Thermal insulation is the reduction of the transfer of heat from a hotter area to a colder one. Thermal insulation is used for three distinct purposes: to keep something hot; to keep something cold; and to maintain something at a roughly steady temperature. Heat is transferred in three ways, conduction, convection, and radiation. The Dewar flask, or vacuum bottle, thus uses three different techniques to reduce heat transfer: a vacuum between the walls to combat conduction and convection; silvered walls to minimize the transmission of radiant heat from one wall and maximize its reflection from the other; and supports for the inner bottle made of cork, a poor thermal conductor.