Product Description:

Knauf DriTherm Cavity Slab 37 is a non-combustible, water-repellent glass mineral wool slab for full-fill insulation of external masonry cavity walls. Supplied at 150mm thick in 1200 x 455mm slabs covering 4.36m² per pack, it is built into the cavity as the wall is constructed, on new build housing, extensions, and outbuildings.

At 150mm, this is the depth specified where a demanding U-value has to be met and the cavity has been designed wide enough to take it. The 37 designation refers to the slab's thermal conductivity of 0.037 W/mK, which at this thickness gives an R-value of around 4.05 m²K/W. Where a tighter target has to be hit at the same cavity width, DriTherm 32 is the higher-performing alternative.

The slab carries a Euroclass A1 fire classification, the highest available, meaning it makes no contribution to fire — an increasingly important consideration in external wall construction. A water-repellent additive runs through the slab, so moisture crossing the outer leaf in driving rain is shed rather than absorbed, keeping the insulation dry and its performance intact. Being semi-rigid and slightly compressible, the slabs push tightly against the masonry on both sides, close up around wall ties, and take up the irregularities in blockwork and mortar squeeze that leave air gaps behind a rigid board. Build in as the inner leaf rises, fit tightly with no gaps at joints, and keep clear of mortar droppings, which would bridge the cavity.

Specification: