“Haus Hohlen” was originally built in 1961.
The building is situated on a hill above Dornbirn, Austria. The site, which is protected on the uphill side by a small forest, provides an astonishing view over the Rhine delta and Lake Constance. In 2012 the house, with an area of 85 m², became too small for its four inhabitants and had to be expanded fundamentally. In the beginning, “Haus Hohlen” was gutted due to the fact that the existing stonework was the only building structure worth preserving. Obsolete fixtures and ineffectual refurbishments were dismantled.
Given the need to increase the amount of space and renew the façade, the idea came up to construct a new building envelope a certain distance around the old house. The chosen lightweight timber stick-construction offers all the advantages of modern timber structures: High prefabrication level, quick construction, sustainability and a good indoor climate. The wooden frame construction is intended as a spatial contrast to the existing solid structure. The existing roof was extended 4 meters on the verges sides and 1.5 meters on the eaves sides.
Due to the position of “Haus Hohlen” in the middle of a natural setting, a large amount of glass was used. Well-proportioned windows offer great views to the valley and the forest. Together with randomly arrayed closed wall elements, the windows generate a sophisticated pattern façade which offers both open and more shielded spaces indoors. Inside, it was important to keep the old house’s structure recognizable within the new: Old windows became passageways, an old kitchen window became a pass-through; another window became a niche for a basin.
The new building skin with up-to-date, highly effective insulation and triple glazing guarantees very low energy consumption. The insulation is made of organic materials such as wood fibre or foam glass. A new heat pump with geothermal probes replaces the existing oil heating. All rooms are equipped with floor heating, and therefore a new screed was necessary for the whole building. The screed’s surface was merely sanded, no additional flooring was used. Now a new homogenous floor surface visually connects the old and new parts of the building. The new façade is a wood-aluminium frame system. All unglazed parts are filled with wooden panels that are covered with a water vapour permeable coating often used in boat building. The dark colour harmonises with the forest in the background.