Knauf Dritherm 37 Cavity Wall Insulation

A lightweight and fire resistant cavity wall insulation made from glass mineral wool, Knauf Dritherm 37 is designed for use in the construction of masonry cavity walls. Due to it’s slightly lower conductivity value of 0.037 W/mK it can be more cost effective alternative to Knauf Dritherm 32, particularly if it is used in conjunction with other insulating methods to reach a required u-value.

Knauf Dritherm is a full-fill cavity wall insulation designed to fill the entire cavity in masonry cavity walls. It is applied during the process of constructing cavity walls and is intended to friction fit - meaning it sits snug within the cavity between wall-ties, with no additional fixings required. 

Dritherm 37 cavity wall insulation is a glass mineral wool designed to be a lightweight, water-resistant and highly non-combustible, fire-resistant thermal insulation. This can often be more forgiving than rigid insulation as it’s fibrous and flexible nature allows it to knit together to prevent air gaps which can compromise effectiveness. It is bound with a unique ECOSE® technology to help it form a solid matt, without the added formaldehyde or phenol. This is visible in the brown colour, as opposed to the more yellowish hue common in other glass mineral wools. 

Cavity Wall insulation is a type of insulation applied within the cavity walls (usually the exterior) of residential and commercial buildings. Many people are familiar with the form of cavity wall insulation that involves blowing small foam pellets into the cavity of existing houses, but modern houses are instead often built using Cavity Slab insulation batts - such as Knauf Dritherm 32 and 37. Instead of being applied retroactively, this is added during the process of constructing the wall - literally from the ground up. It is designed to “friction fit” between the cavity walls, in between the steel wall ties, and is an effective thermal insulation.

Mineral wool insulation is a type of insulation material made from natural minerals like glass or rock, which are melted down and spun into fibres. These fibres are then compressed into mats or formed into batts, boards, or loose-fill insulation products. Mineral wool is known for its excellent thermal insulation properties, as well as its ability to resist fire, moisture, and pests. It is commonly used in residential and commercial buildings to improve energy efficiency by reducing heat transfer through walls, ceilings, and floors. Additionally, mineral wool is favoured for its durability and resistance to mould and mildew, making it a popular choice for both new construction and retrofit projects. Knauf insulation is predominantly made with glass mineral wool.

Knauf Dritherm 37 comes in packs of “slabs” - the quantity of which varies depending on thickness. Each slab measures 1200mm in length x 455mm width - designed to fit standard vertical wall tie spacings, allowing a closed joint with adjacent slabs. It is available several thicknesses: 

50mm, 75mm, 85mm, 100mm

Which are common sizes for wall cavities. Knauf Dritherm is a full-fill insulation, meaning you should choose a thickness the same size as the wall cavity. 

Knauf Dritherm is a cavity wall insulation, meaning it is applied within the cavity of masonry cavity walls during their construction. It is built up along with either sides of a cavity wall and added as the courses of masonry and corresponding wall-ties are added. It is cut into 1200mm x 455mm sheets designed specifically to fit between these ties. Ensure you select a thickness that corresponds to the space of the cavity. Designed as a full-fill insulation, this insulation is designed to have full contact with the wall, so special care must be taken to avoid thermal bridging. 

Calculating the U-Value is often important to ensure your project complies to the appropriate building regulations, and create a warm and fuel-efficient structure. Use the Knauf U-Value Calculator to help you calculate the u-value of your project.