This was phase two of a multi-staged project to build new council homes on existing council-owned land. Typical sites for the project included disused garages and areas of waste ground between developments. The dwellings were all built to Code Level 4 of the Code for Sustainable Homes. Although in advance of the existing building regulations, this objective fitted with the government aim of encouraging government agencies to increase standards of sustainability.
To achieve this rating, the construction elements needed a high level of thermal insulation. The Rå Build method using the H+H Thin Joint masonry system was specified using Jumbo Bloks. Fully filled cavities were combined with either aircrete or brick outer leaves. This is not only an extremely fast and efficient method of building, but also provides substantial benefits in reducing heat loss. In designing the wall structure, the use of aircrete’s very low psi values, based on Accredited Construction Details, allowed a halving of the y-value from 0.08 to 0.04 W/m2K. This is used to calculate the impact of linear thermal bridging within SAP 2005. The 0.04 y-value is achieved by virtue of the thermal efficiency of aircrete, without the need to resort to Enhanced Construction Details, and has a similar effect on all external elements.