Andrew Gill, who is a self-builder and low energy retrofitter, recognised the need for affordable, low-energy housing, and undertook an ambitious project to prove that the cost-effective refurbishment of existing housing stock is a viable possibility. He challenged himself with the complete renovation of a dilapidated terraced house in Manchester.
Adopting a 'fabric first' approach, Andrew’s key objectives throughout the project were: increasing insulation, improving air-tightness, managing ventilation and limiting embodied energy within the refurbishment. Most importantly, he was adamant that improved insulation and air-tightness must work in tandem, to ensure maximum efficiency.
Andrew turned to Knauf Insulation to supply insulation measures throughout the property.
Knauf's ThermoShell® Internal Wall Insulation (IWI) System was used throughout the property at a thickness of 60mm. Specifically designed to upgrade the thermal efficiency of solid walls, IWI can accommodate wall imperfections or fixings for fittings, and can be adapted around openings such as windows and doors.
In addition, as it is a full-fill solution, the ThermoShell IWI system prevents air movement within the wall and reduces air leakage – a key consideration for Andrew and his goal of achieving maximum air-tightness.
ThermoShell IWI comprises EcoStuds - extruded polystyrene laminated to Oriented Strand Board (OSB), which are mechanically fixed to the internal wall to create a frame for the system (image 2). As the system uses an insulating material to form the frame, rather than timber or metal, it reduces cold bridging and allows for a thinner system to be used to deliver the thermal performance required.
Earthwool EcoBatt water repellent glass mineral wool slabs are then friction fitted between the EcoStuds and faced with either a vapour check plasterboard sheet or a vapour control layer and standard plasterboard, which is the option Andrew chose. The Earthwool EcoBatts fully fill the insulation zone and are in intimate contact with the EcoStuds and plasterboard, thereby preventing any air or draught movement within the system.
As well as the IWI system, Andrew installed Knauf Insulation’s Earthwool Loft Roll 44 in varying thicknesses around the house, including 440mm in the roof cavity, 100mm in the intermediate floor (image 3), 100mm beneath the stairs and 200mm in the suspended timber ground floor, which was combined with 25mm of Polyfoam ECO Floorboard.
Finally, Andrew installed Knauf insulated plasterboard in 27mm and 35mm thicknesses along the party walls at the junction with the exterior walls, and around the window and door reveals, to further minimise cold bridging.
Andrew has conducted analytical modelling of the property, which suggests an energy reduction of 62 per cent and carbon reduction of 57 per cent compared to its previous condition. In addition, the property is expected to achieve a band ‘C’ Energy Performance Certificate rating, a significant improvement on the band ‘F’ that it held previously.
“I am pleased with the results of the insulation and with the simplicity of the IWI system,” Andrew continued. “The property has been air-tightness tested with excellent results that sit firmly at the top end of retrofit best practice, short of attaining Passivhaus standards. In addition, I’ve achieved excellent levels of thermal efficiency – the U-value in the loft, for example, is just 0.05 W/m2K, which is a fantastic improvement and a big step towards my ultimate aim of proving that cost-effective energy refurbishment is a realistic goal.”