Sustainable insulation delivers high thermal performance in extension to historic home

Challenge

The Bluestone House was built in 1909 and the current homeowners wanted to create a larger living area and more comfortable environment by adding an extension. To maintain the integrity of the building, the extension was built with calcrete or limestone paddock stone.

Solution

When considering the best insulation product to provide high thermal performance that would also be suitable for fully filling the cavity in the calcrete extension walls, homeowner Sharon Rowett chose Earthwool® DriTherm® Cavity slab. The product is silicone treated and semi-rigid with a high vapour resistivity to prevent moisture transmission to the inner leaf. "It was important that the extension complemented the original building, which is why we chose to use calcrete; however, we also wanted to ensure the walls had high thermal performance and after doing some research and from the advice of our builder we decided to go with DriTherm® Cavity slab,” said Sharon.

"We also required an insulation product that would withstand weather variance and in particular, rain, and the moisture resisting properties of DriTherm® Cavity slab made it ideal for the extension.”

Another key factor in the choice of this product was Knauf Insulation’s approach to environmental considerations. 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. "I was pleased to find that Knauf Insulation had introduced their leading cavity wall insulation into Australia. It was important for us to use a product that had high sustainability credentials and DriTherm® Cavity slab met this criterion and more,” Sharon added.

"Because DriTherm® Cavity slab is silicone treated, water cannot pass from the outer wall to the inner wall, which eased any concerns we had about moisture entering the house. The 50-year warranty also gave us added peace of mind.”

DriTherm® Cavity slab is CodeMark™ certified and has been successful in the UK for several years and has also been used in Passive House applications where the design focus is to significantly lower energy consumption and the impact on the environment. The history of use coupled with the proven material performance of 1.4 m²K/W, also ensured that not only was the environmental criteria satisfied but also high thermal performance would be achieved.

"The team at Knauf Insulation were incredibly helpful and the service provided was excellent,” Sharon added.