The most important reason for renovating Danish housing estates from the post war period has been adaptation to increasing demands on energy conservation, but decay of materials and constructions in the façade, leaking roofs and penetrating water have also necessitated reconstruction and modernisation of façades in the housing stock from that period. The Danish way of renovating is however multifaceted. There is not a single or a general method or technology. The original external walls can be divided in three different constructions: traditional masonry cavity walls, the industrialised concrete sandwich wall and finally the light-weight wooden façade system with plates or boards of wood, fibercement or other materials as cladding.

The general problems are most significant for the non traditional built external walls, and they are most commonly renovated by adding an external secondary lightweight construction with extra insulation and new cladding, which might be with or without ventilation behind. The article gives a general description of the performance of the construction and 2 cases representing renovation of sandwich and lightweight constructions respectively.