The existing house is part of a typical post-war housing estate. It is a one-storey single house with an adapted attic, built by simple and cheap materials with a minimum floor area (7.90x6.10m) footprint. The main reasons for the refurbishment and the extension were the need for more comfort and space, in addition to the need to reduce expensive heating costs and the constant cold, which were aggravated by the fact that the owner was not using the house permanently. Furthermore, the client requested that the house should offer an additional orientation to the garden lying westward and a better image, since it was going to be used for therapy sessions as well. General refurbishment of the existing furnishings was necessary, and its living room needed enlargement. Another requirement was that the client should supervise and manage the construction herself. The architect's interventions were limited to: • Breaking open the south west masonry corner of the living room and attaching a winter garden (sun space) to the existing house. The main concept behind this measure was to enlarge the living room optically as well as to enlarge it physically through the use of large sliding glass doors. • The glass panes of the winter garden face exactly south, while the curved masonry back wall is oriented towards the garden to the west, with its window openings progressing in size in the direction of the garden. • Since the attached winter garden is 1 ½ stories high, it is connected thermally to the existing attic at its floor level. The upper part of the winter garden is equipped with vents which allow the heated air to flow by convection to the floor of the bedroom in the attic. • Due to the use of exterior thermal insulation and passive solar energy, the total energy consumption of the house was reduced to quarter of the previous level, despite an increase of 25% in the floor area.