Using Thermalite blocks in the inner leaf of the cavity wall can meet U-values down to 0.17 W/m2K with a 300mm footprint. If Thermalite Enhanced Construction Details are used, this will also dramatically reduce the heat loss through thermal bridging at the junctions of elements. The heat loss reduction is about half that of the standard Accredited Construction Details and, in real terms, can help to reduce or eliminate the amount of renewables required for a dwelling.
Another factor in meeting Part L is air permeability. Thermalite is inherently airtight with block permeability figures of <0.10 m3/(h.m2), meaning that, with good workmanship, fabric airtightness figures down to 3 m3/(h.m2) can be easily achieved.
Part L 2010 incorporates heat loss through clear cavities in party walls, which was not previously recognised under the old regulations. This heat loss is significant but can be eliminated using full fill mineral wool, coupled with effective edge sealing. Thermalite can provide a range of separating wall Robust detail solutions that meet this criteria.
Thermalite’s other environmental benefits, including a ‘very good’ rating under BES6001 – the responsible sourcing standard – and Green Guide A+ ratings for external walls, additionally give a very sustainable approach to the fabric of a building.