The Barratt Green House, an award-winning zero carbon prototype house voted for by 22,000 readers in The Mail on Sunday British Homes Awards, has been wrapped with weber.therm XM, the innovative external wall insulation system manufactured by Weber.

The Barratt Green House is a showcase for new technology, new systems and materials which collectively will meet the highest level six of the Government’s Code for Sustainable Homes. The Barratt Green House exceeds the eco-requirements originally stipulated following a two year period of scientific testing to assess every aspect of the design, construction and materials used in a collaboration led by the National Centre for Excellence in Housing.

In the Barratt Green House, weber.therm XM – high performance external wall insulation – has been applied to the lightweight aircrete panel structure on all external walls. The system was installed by Weber recommended specialist applicator, The BDL Group PLC of Uxbridge, Middlesex. EWI has many advantages and easily out-performs the option of internal insulation where floor area and usable space is compromised. Internal insulation also has the inherent risk of isolating the structural wall from the heat source within the building thereby reducing the temperature of the outside of the wall. In this situation the installation of an unbroken vapour barrier is required on the warm side of the construction to avoid the consequences of interstitial condensation.

Alternatively, using traditional insulation in the cavity has similar constraints in terms of the limited size of the cavity space. The resulting colder outer leaf can again give rise to interstitial condensation problems resulting in wet insulation, reduced thermal performance, and failure when subjected to the freeze thaw cycle at very low temperatures.

The weber.therm XM insulation system has been designed to meet the stringent U value required and consists of a layered sequence of applied materials which are mechanically and adhesively fixed to the exterior substructure. The build-up consists of 180mm phenolic insulation applied to the substrate using mechanical fixings; a base coat of weber.rend LAC incorporating a glass woven reinforcing mesh and further coat of weber.rend LAC; a primer coat of weber PR310 followed by weber.plast TF150, an acrylic based, synthetic textured finish.

The Barratt Green House has been constructed using many cutting edge materials and systems including the use of 180mm phenolic insulation combined with the lightweight aircrete panels to provide the required U-value of 0.12 W/m²K; heat which is produced by an Air Source Heat Pump; hot water supplied by a solar hot water panel; automatic window shutters to prevent over-heating of the house during summer and a rainwater harvesting system. Due to the collective performance in the Barratt Green House there will be no need for appliances such as radiators – or even a tumble drier!

The use of Weber EWI on single leaf or solid wall construction is a revolutionary system which stabilises the structure keeping it warm and free from degradation. In this new build situation construction is simplified contributing significantly to fast track application and a high performance building. The use of Weber's EWI systems are equally suited to the thermal upgrading of existing properties, particularly solid wall non-traditional housing.