
What size clear cavity do I need for partial fill cavity wall insulation?
Find out why a clear cavity might be needed and how exposure risk is assessed







Kooltherm K8 Plus is a cavity wall insulation board that only requires a 20 mm clear cavity. A thermal conductivity as low as 0.021 W/mK can allow for a thin cavity wall construction and can maximise usable internal floor space.
Product Highlights
Thinner walls can allow more natural daylight into your building
20 mm clear cavity is maintained - resists moisture penetration
Standard details available for key junctions
Low emissivity foil facings increase the thermal resistance of the cavity
Lightweight insulation that is easy to cut and work around awkward detail