Thermal insulation

thermal insulation reduces unwanted heat exchange. Conduction through supports, convection in gas and thermal radiation require different treatments. vacuum suppresses gas transport but leaves solid conduction and radiation; lowering thermal conductance also increases the temperature rise caused by a fixed internal heat load.

A thermal shield reduces coupling to unwanted environmental temperature changes. Low-conductance supports and thermal insulation reduce heat transport, low-emissivity surfaces reduce thermal radiation, and a conducting inner enclosure can reduce temperature gradients. Combined with heat capacity these give a thermal low-pass response. Passive shielding cannot indefinitely reject a slow change in the entire environment and may increase the temperature rise from internal dissipation; active regulation addresses a different frequency range.