The Energy House project was the result of collaboration between partners: Isover; the University of Salford; Leeds Metropolitan University; research centre, Saint-Gobain Recherché; and other Saint-Gobain businesses including British Gypsum, Glassolutions, and Saint-Gobain Weber. Their aim was to investigate how to maximise the thermal efficiency of the UK’s ageing housing stock.
The study began with a full-scale replica of a 1919 end-of-terrace house and was carried out over three months and in six stages, allowing researchers to accurately monitor the impact of the retrofitted solutions on thermal performance. This ‘baseline’ building, situated in an environmentally-controlled chamber in the University of Salford’s Energy Hub, featured energy efficiency measures typical of 1990s renovation work, including double-glazing and 100mm loft insulation to represent the majority of housing in the UK.
Carrying out the work
During the first phase of the project, Isover’s 170mm Spacesaver insulation was used to upgrade the energy performance of the loft. The mineral wool quilt was installed on top of the existing 100mm material to bring the loft insulation up to date with current building standards. This reduced heat loss from an initial 187.5W/mK measured in the ‘baseline’ house to 180.5W/mK. This is significant considering it is by far the cheapest and least intrusive of all the measures applied to the house, resulting in the quickest return on investment.
Isover’s Renovation Roll Thermal was chosen to insulate the floor due to its high-performance and the ease of installation it offered, which made it ideal for retrofit projects. The 200mm was fitted between the floor’s supporting joists to reduce thermal conductivity in the base of the building, before being overlaid with Vario KM Duplex Climate airtightness membrane. This provides a unique combination of materials to ensure thermal comfort while minimising air leakage and actively controlling moisture in the construction, protecting the floor’s timber structure from the damage it can cause.
Making an impact
The installation of Isover’s floor solutions cut air leakage in the house from 10.4m3/(h.m2) to just 6m3/(h.m2). Heat loss through the building fabric was also reduced from 82.7W/mK to as little as 69.7W/mK. This accounted for more than 17 per cent of the improvement in thermal performance for the house.
In addition, Isover’s upgrades to the floor insulation ensured the temperature in the room was much more even. In areas where there was previously a 5°C temperature difference between typical head and foot height, this difference was reduced to less than 2°C, acknowledged as being comfortable for residents.
The whole house Saint-Gobain retrofitted resulted in a reduction in heat loss of up to 63 per cent. In addition, researchers found that air leakage through the building fabric was halved from 12.5m3/(h.m2) at 50 Pascals (Pa) to just 6m3/(h.m2) — more than 42 per cent of which was the result of the installation of the Vario membrane in the floor construction. In an actual house, this would further boost energy efficiency and enhance thermal comfort for building occupants, through the reduction in draughts.
Speaking about Isover’s involvement in the project, Tom Cox, Product and Systems Development Manager at Isover, explained: “This was a fascinating opportunity for us to thoroughly understand the impact that a full retrofit can have on a typical UK home.
“To reflect the realities of a standard renovation project, it was necessary to select solutions that could work effectively as part of a ‘whole house’ retrofitting approach, involving multiple technologies. The products and systems Isover used were not only able to achieve this, but could be easily cut to size and fitted into standard loft and floor spaces, simplifying and speeding up the installation process.”
Simon Gibson, Research and Development Manager at Saint-Gobain UK and the leader of the Energy House project, added: “The impact of the whole house retrofit on energy efficiency, and the solutions provided by Isover, has been highly significant. Taking an average 2012 gas fuel price for the area where the project took place, we worked out that the newly-renovated building could be heated for less than £4 a week - a saving of £348 per year on the heating bill for the property.”