Cavity slabs are thermal insulation products for the external masonry cavity walls of buildings, used to reduce heat loss and improve energy efficiency by fully filling the wall cavity, offering thermal, acoustic, and moisture-resistant benefits. The main difference between Knauf Dritherm 32 and Dritherm 37 is their thermal conductivity, with the Dritherm 32 (0.032 W/mK) offering superior insulation performance to the Dritherm 37 (0.037 W/mK). This means Dritherm 32 will provide more thermal resistance and thus better energy efficiency. Consequently, Dritherm 32 is the higher-performing, more expensive option, while Dritherm 37 is a standard, cost-effective choice.