Cavity wall insulation is used to reduce heat loss through a cavity wall by filling the air space with material that inhibits heat transfer. This immobilises the air within the cavity (air is still the actual insulator), preventing convection, and can substantially reduce heating costs. Cavity Wall Insulation is installed by drilling a set pattern of holes into the mortar joints on the outside of the property, and insulation is injected into the cavity. The insulation is gravity fed from the bottom up.

Retrofit cavity wall insulation systems are installed as a system (normally installed to the entire property) and typically holds a 25-year guarantee (normally from CIGA – Cavity Insulation Guarantee Agency) from the date of installation. Clause 2 of the Guarantee states that altering or disturbing cavity wall insulation system (even in one area of the property) invalidates the guarantee in its entirety leaving the insured without a guarantee therefore, the insured are not left in a pre-loss condition.

Insulation materials itself do not retain heat, it is the air pockets contained within the material that retains heat and this creates a U-Value (typically the lower U-Value rating, the more heat it retains). Should the product be affected by any of the specified perils, the air pockets can become compressed therefore losing its ability to retain heat.