Haus Hoinka by Stuttgart-based Atelier Kaiser Shen is described as “a straw bale house in the village center.” Located in Pfaffenhofen, a small historic village close to the city of Heilbronn in south-western Germany, Haus Hoinka’s design is typical of the regional vernacular.
Haus Hoinka was crafted using natural and renewable raw materials; in effect, the structure's individual components can be recycled and reintroduced into nature. “Everything was based on the idea of using bales of straw combined with clay plaster as a thermal envelope,” explains Atelier Kaiser Shen. “The goal for Haus Hoinka was to realize all six facades — including the roof and the floor slab — using this straw bale construction method.” The method presses bales of straw into a wooden framework to a thickness of 36.5 cm. A traditional practice that dates from the late 19th century, the popularity of straw bale construction is growing due to the ecological sustainability of straw — an organic material, straw is locally sourced, easily available, and recyclable. Moreover, it is relatively inexpensive.
Dispensing with the elaborate process of sealing and waterproofing the straw bales, Atelier Kaiser Shen chose to raise the building of the ground: “The compact house rests on a concrete cross and four supports,” explains the architect. “When the wooden shutters are closed, it creates the impression of an elevated wooden monolith.” Haus Hoinka’s grain and roof are in keeping with the village setting. Its stone base and wood cantilever are designed to ensure an architectural dialogue with the half-timbered houses that characterize Pfaffenhofen.
House Hoinka’s simple outer form conceals the fact that it is a semi-detached property: two residential units are each connected to the garden level via a single flight of stairs — the entrance doors are each located on the ground floor. The house is divided lengthwise on the first floor and crosswise on the second floor, ensuring residents can benefit from all-round views.
On both floors, eight rooms that measure approximately 4 x 4 meters are designed in a manner that is unspecified (with the exception of the already installed bathrooms). On the ground floor, the concrete cross and four corner supports (that elevate the house), create four open spaces. “The client decided to realize a granny flat in one of these four spaces,” says the architect, “and further developments such as a winter garden, workshop, or guest room are possible future options.”
Uniformity in design is a key aspect of House Hoinka. “The uniformity in the rooms is also reflected in the facade,” says the architect. “All rooms on the upper floors have identically shaped windows, with only the balcony doors interrupting the [flow].” In the attic, "wide ribbon windows were installed and are identical in form.” The notion of uniformity extends to the overall configuration of the house. It is possible to further divide the two semi-detached units by floor, creating four small apartments. “In this scenario,” says the architect, “the internal staircase becomes a stairwell that provides access to two residential units.” This flexible design ensures the house is an adaptable residence that can meet future changes in living circumstances.
House Hoinka’s ecological credentials extend to its use of regenerative sources of energy. Electricity is generated by solar panels integrated into the roof as a complete water-bearing layer. “The solar modules form the smallest component in the house and correspond with the grid of the skylights as well as with the grid of the house as a whole,” says Atelier Kaiser Shen. Describing the building as one with a “particularly good eco-balance,” the architect says that “compared to a new conventional semi-detached house of the same size, made of bricks or tiles and with classic insulation, 95 percent of CO2 has been saved. Around 100 tons of CO2 are stored in the 140 cubic meters of wood used for the house.”
In House Hoinka, the benefits of utilizing a renewable insulating material such as straw are clearly evident. Furthermore, Atelier Kaiser Shen demonstrate that a straw bale house makes for a truly aesthetic abode.