What are the best thermal insulators?

Answer by  quisqualis (1756)

The best thermal insulators do not conduct heat, have no convection, and do not transmit heat. Therefore, they should be solid and not transparent, and full of empty air spaces. Wood and asbestos are both excellent insulators. Asbestos is better in high temperature environments.

Answer by  caftril (176)

Dry, still air trapped in fiberglas, rockwool, double-paned glass windows, or even between outer plywood and inner drywall is the most commonly used thermal insulator. Foam, putty, caulking and other materials are used to stop air leaks or infiltration. Moisture control with proper roofing or siding prevent the air-trapping materials from being compromised.