For questions about thermal insulation used to reduce the rate of heat transfer. Can be used for buildings, people (e.g. clothing) or other applications where it is desirable to maintain a higher or lower temperature than the surroundings.

Whenever two regions of different temperature are in contact, heat will flow from the warmer region to the colder region, at a rate proportional to the difference in temperature (referred to as ΔT, "delta T").

This flow of heat is undesirable in certain circumstances, when a person/s, place, or object needs to be maintained at a specific temperature or range that is different from its surroundings in order to function properly.

Thermal insulation is any material which can be used at the boundary between two regions of different temperature in order to slow the rate of heat transfer. All materials have a measurable thermal conductivity. Materials with a low thermal conductivity work well as thermal insulation. In addition, some types of insulation function by trapping pockets of air, which has a relatively low thermal conductivity.


Most fabrics have a relatively low thermal conductivity, but some function better as insulation:

  • wool
  • down (natural or synthetic)
  • polyester fleece


Typical building insulating materials include:

  • Fiberglass
  • Rock wool
  • Cellulose
  • Vermiculite
  • Foam
  • Perlite
  • Cork


Other applications of thermal insulation include:

  • Refrigerators, freezers, and coolers/ice chests
  • Ovens, toasters, and microwaves
  • Hot water heaters and storage tanks
  • Piping and ductwork used for heating and cooling