Insulation trade jargon

Jargon by trade
Cavity wall

Wall made up to two parallel masonry skins, with an air space between them to aid ventilation.

External wall insulation (EWI)

A layer of insulation affixed to an external wall, covered with reinforcement then finished with a special form of render.

Full-fill cavity

A wall cavity that has been completely filled with insulation.

Glass wool insulation

Insulation made from layers of glass fibre, compressed together.


A material which helps prevent the transfer of heat from one object to another.

Internal wall insulation (IWI)

A form of insulation where insulating boards are added to the interior of a wall.


Insulation around pipes to help regulate their temperature.

Mineral wool insulation

A term for fibrous insulation made of materials such as stone or glass.


Multifoil insulation

Insulation constructed from multiple layers of aluminium covered in plastic foil.


Partial-fill cavity

A wall cavity that has not been entirely filled with insulation.

Sheep wool insulation

Insulation made from sheep’s wool, which can be formed into different shapes depending on usage.

Solid wall insulation (SWI)

Typically found in older houses built before the 1930s, homes with solid wall insulation lose more heat than those with cavity wall insulation.


Stone wool insulation

Similar to glass wool insulation, but made of volcanic stone and able to withstand higher temperatures.

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