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Many ways of improving U-values of cement based materials are feasible. Often these involve creating a composite construction, such as expanded polystyrene and concrete.
One example is the nu-Trenchfloor system. This incorporates an insulating layer of expanded polystyrene at the edges and beneath the ground bearing concrete slab. Aerated concrete blocks have low density and their cellular structure gives good insulating performance, especially when coupled with suitable cavity and insulation designs.
Reduced thermal conductivity can be achieved by the use of thin mortar jointed systems for block wall construction. These very thin joints (<3mm) reduce the heat loss at the block/mortar interface, with the added advantage of facilitating the more rapid construction of walls.
For further information see U-values: understanding heat movement, published in CONCRETE in March 2003, pp 42–43. Copies are available as a free download from the Members Area of the Concrete Society web site.