Earthwool cavity wall insulation from Knauf Insulation was chosen by the owner of the Bluestone House to ensure high thermal performance in the extension being built to the existing structure.

Originally built in 1909, the Bluestone House was extended by the current homeowners to create a larger living area and more comfortable environment. The integrity of the building was maintained by constructing the extension with calcrete or limestone paddock stone.

The insulation product not only needed to provide high thermal performance but was also required to fill the cavity in the calcrete extension walls. Homeowner Sharon Rowett chose Earthwool DriTherm Cavity slab as it met these requirements. The product is silicone treated and semi-rigid with high vapour resistivity to prevent moisture transmission to the inner leaf.

Sharon Rowett explained that they chose calcrete as it was important for the extension to complement the original building; they also wanted to ensure the walls had high thermal performance and therefore, selected DriTherm Cavity slab for the application. The insulation product was required to withstand weather variance and in particular, rain, and the moisture resisting properties of DriTherm Cavity slab made it ideal for the extension.

Knauf Insulation’s approach to environmental considerations was also another key factor in the choice of this product. Knauf’s leading cavity wall insulation product, DriTherm Cavity slab is made using recycled glass bottles and ECOSE Technology, a formaldehyde-free binder based on rapidly renewable materials instead of petro-based chemicals.

According to Sharon, DriTherm Cavity slab also met their requirement for a product with high sustainability credentials. Being silicone treated, DriTherm Cavity slab does not allow water to pass from the outer wall to the inner wall, which eased any concerns about moisture entering the house. The 50-year warranty also gave them added peace of mind.

DriTherm Cavity slab is CodeMark certified and has been successful in the UK for several years. The cavity wall insulation product has also been used in PassivHaus applications where the design focus is to significantly lower energy consumption and impact on the environment.

DriTherm Cavity slab’s proven application and material performance of 1.4 m²K/W also ensured that the product met the environmental criteria as well as high thermal performance requirements.