Thermal insulation

Thermal insulation uses materials or structures to slow heat transfer between regions at different temperatures. It works by limiting conduction, convection, or radiation.

Thermal conductivity: A material property that measures how readily heat flows through a substance. Low conductivity reduces heat flow through solid insulation.
Porosity: The fraction of a material's volume occupied by pores or voids. Porous insulation traps gas in small spaces, limiting heat flow.
Building envelope: The physical boundary separating a building's interior from its exterior environment. Insulation in walls, roofs, and floors limits heat exchange across this boundary.
Thermal mass: A structure's capacity to absorb and store heat, influenced by its mass and heat capacity. Thermal mass stores heat; insulation slows its movement through boundaries.
Conduction: Heat transfer through direct interactions between particles or through moving electrons in a material. Solid insulation mainly limits heat transfer by conduction.
Specific heat capacity: The heat energy required to raise a unit mass of a substance by one degree. It distinguishes heat storage from insulation's resistance to heat flow.
Cavity wall insulation: Insulation installed in the gap between the inner and outer leaves of a cavity wall. It applies thermal insulation within a common wall construction.
Radiant barrier: A low-emissivity surface designed to reduce radiant heat transfer, often across an air space. It targets radiation specifically rather than reducing all heat-transfer modes.
Convection: Heat transfer by the bulk movement of fluids such as liquids and gases. Insulation cavities suppress convection when they prevent air circulation.
Thermal diffusivity: A measure of how quickly temperature changes spread through a material. Low diffusivity slows temperature swings but does not alone establish steady-state insulation.

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