Residential house "Im Moos", Windisch/AG

The single-family house "Im Moos" was built in 1968 by architect Hans Kuhn for a civil engineer and his family. Hans Kuhn designed the Villnachern school building in the region, for example. His buildings reflect the moderate Scandinavian modernism that was gaining a foothold in Switzerland at the time: clear lines contrast a generous use of spruce and oak wood, rough plaster structures meet exposed concrete with a clearly legible board structure.

The architecture was largely in its original condition and showed a high design quality. Structurally, there were few defects to be located, a solid construction that had been well maintained.

However, the house, like many of its contemporaries, showed greater energy-saving potential: The walls were weak, the roof barely insulated, the outer shell only conditionally airtight. Thermal bridges were compensated locally with generous use of heating energy. Heating was provided by an oil-fired heating system.

The roof and basement were comprehensively insulated, and the windows including the frames were replaced. Thermal bridges were lined with Aerogel. A special challenge was the replacement of the large-format terrace windows, probably because they still dated from that time. The old roller shutters were later replaced by venetian blinds, and new awnings were installed.

The client was also keen to preserve the existing qualities. Spatial changes were only made in the area of the central living room: the kitchen was brought a little closer to it and the somewhat hermetic hatch was replaced by an open buffet.

Existing fixtures and surfaces were largely retained, for example the tiles in the bathrooms. Defective areas were artfully replaced and adapted to the new sanitary appliances. An oiled parquet floor was used, and the originally white walls were dipped in a soft "terre d'ombre".

About the energy concept

Heat generation was evaluated in several variants. The evaluation process retrospectively sheds light on the challenges we will face to achieve the 2050 climate target.

A PVA on the available roof area could have generated far more than the annual energy demand, and the house could have been self-sufficient via a heat pump. The payback would have been < 15 years even with an aesthetically pleasing, fully integrated PVA.

The big challenge, which is unfortunately still little discussed in public, is the storage of energy over the heating period when the sun is low. Even in the best case, the payback of a storage system is still over 40 years. However, technical development makes us optimistic in the medium term.

Currently, however, more and more PVAs are feeding more and more electricity into the grid on sunny days. As long as this electricity cannot be "hibernated" at a favourable price, this will have a negative impact on the feed-in tariffs. Here, too, the incentive now drops to the almost symbolic 7 m2 that can be used to cover a daily cycle in summer.

In the present case, the building owner finally decided on a pellet heating system. In this case, a sensible decision.  The heating oil tank had been generously dimensioned and offered space for a 7-to. pellet store. In 15 years, energy storage will hopefully have advanced to the point where a heat pump can be operated with the stored electricity from a PVA.


Overall management, architecture, construction management

Planning team
Civil engineer: MWV Bauingenieure AG, Baden
Building physics: Amstein + Walthert, Zurich

Realisation June 2021 to October 2021