This project represents the first furniture store in Europe to be built to Passive House standards. The company that operates out of the building, Kohler, specializes in high-quality and ecological solid wood furniture. As their operating philosophy had to be highlighted by the building’s design, it made sense to construct the entire building using ecological timber construction in conjunction with solid, heat-storing solid building materials. The round roof shape down to the floor slab in the south-west could only be achieved in the cheapest and easiest way with highly insulated wooden structures.
Due to the requirement to use as much natural materials as possible, while at the same time being forced to save as much as possible, the author took up a research project he had initiated and worked on for wood research in Munich under Prof. Dr. Gerd Wegener in which untreated wood shavings were researched for insulation purposes and were metrologically examined in the author's house over two years. The advantage was that the wood shavings are 90% cheaper than commercially available insulation materials. The heat conductivity is in the compressed, settlement-safe state of approximately 120 kg / m³ at a λ = 0.55 W / mK.
The wall thickness had to be increased by 30% in order to compensate for the lower thermal insulation compared to an insulation material of the WLG 040l, which hardly plays a role in the timber construction, since the quantity of the panel materials increases only slightly. As a result, the savings in insulation material were over € 30,000. In addition, the heavy wood shavings with a compression of 120 kg / m³ also entail very good heat storage.
The total net floor area is approximately 1,300 m2, and 1,000 m2 of that space is sales area. The remaining 300 m² includes office space, sanitary facilities, technical rooms, storage, and a workshop. The building is accessed from the north, meaning the generously glazed entrance area therefore also had to face north. In addition, the solid wood furniture must not be exposed to direct sunlight. For these two reasons, solar gains from solar radiation had to be largely avoided.
[Images courtesy of Keck Architekten GmbH]