It is expected that the heat insulation demands in the Danish Building Regulations will be further increased around 2005, in order to reduce the heating demand and the CO2-emission. A simple increase of the insulation thickness of common wall types seems not to be attractive due to the increased effect of the 2-dimensional heat loss, the large wall thickness, and the costs of the wide foundation. Therefore, new types of walls have been developed. It is sought to minimise the total heat loss as well as the material consumption. The target was to come up with new walls for which the construction costs only are increased by the cost of the increased insulation. Further, the new walls should be based on known materials to ensure that they can be used in 2005. Of course, also the usual requirements to strength and durability must be fulfilled. Detailed heat loss calculations showed that design of the joint between the foundation, the wall, and the floor slap is very important as 2-dimensional heat loss here is quit significant if not taken proper care of (even though it is not accounted for in the present rules). The new wall types were consequently designed jointly with the foundation. Both walls from solid materials as masonry and concrete and framed walls have been dealt with. Three types of foundation and five types of wall have been studied in detail, one of which is just the traditional cavity wall with increased insulation. Cost analysis has proved that the suggested wall types will be economical beneficial over their lifetime, even at present energy costs. Presently, it is sought to build real houses using the developed wall types.