Location: Aberdeen, Scotland
Project Type: Renovation of an early 20th-century building
Products Used: Sisalwool 50mm
Introduction
ABN7 Architects were seeking a natural, breathable insulation solution for a sensitive retrofit project, where maintaining the building’s fabric and indoor air quality was just as important as improving energy performance. They chose Sisalwool to deliver high thermal performance while aligning with low-carbon, fabric-first design principles.
Project Overview
The project involved retrofitting a traditionally built property with solid walls, where standard synthetic insulation risked trapping moisture and compromising the existing structure. ABN7 Architects needed an insulation system that would improve comfort and reduce heat loss without sealing the building in or creating condensation problems over time. The brief called for materials that were sustainable, low-toxicity and compatible with lime-based construction, ensuring the retrofit enhanced rather than harmed the original fabric.
Sisalwool contribution
Sisalwool natural fibre insulation was specified for its combination of thermal performance, vapour openness and sustainability credentials. The product uses a blend of sheep’s wool and sisal fibres, including material repurposed from recycled coffee sacks, supporting a circular economy approach while delivering robust insulation values. In this project, the insulation was installed within timber framing and against solid walls, working in tandem with lime-based finishes to create a breathable build-up that manages moisture safely. Its flexible batts were easy for the contractor to cut and friction-fit, helping to minimise gaps and thermal bridges during installation.
Results
Following installation, the retrofit achieved a noticeable improvement in internal comfort, with warmer surfaces, reduced draughts and more stable indoor temperatures. The breathable build-up supports the movement and release of moisture within the wall, reducing the risk of interstitial condensation and helping to protect the existing structure over the long term. By using a natural fibre solution, the design team also reduced embodied carbon compared to typical synthetic insulation, while providing a healthier indoor environment for occupants.
Conclusion
This project demonstrates how Sisalwool can be successfully integrated into architect-led retrofit schemes where fabric breathability and heritage sensitivity are paramount. For ABN7 Architects, it provided a practical way to meet modern performance expectations with a natural, low-impact insulation that works with, rather than against, traditional construction. It stands as a strong example of how thoughtful material choices can deliver both energy efficiency and long-term resilience in retrofit projects.
“Sisalwool is easy to cut, fast to install and safe to work. It’s bloody brilliant! Also, there was basically no waste as off-cuts could be used elsewhere, unlike PIR"
