Heat transfer occurs in three basic ways: Conduction, convection
and radiation. Convection works on the principle of
gas molecules transferring heat energy to other gas molecules
by bulk movement. Vacuums do not contain any gases and
thus using a vacuum practically eliminates the transfer of heat
due to convection. A vacuum insulated panel (VIP) is one
type of thermal insulation which is based on this concept. It
uses a gas-tight enclosure surrounding a vacuumified core.
VIPs are the most effective insulators and have much lower
thermal conductivities than conventional insulating materials
such as mineral wool or polyurethane foam panels. However,
VIPs do have their drawbacks such as their susceptibility to
detoriation over time and their relatively high cost. Further,
they cannot be cut to fit like traditional insulators since this
would destroy the vacuum. They must, therefore, be ordered
if non-standard sizes are required, further increasing the cost