Family house in Sulzberg

Initial Situation
A family with two children wanted to build both a family house and a neighboring building for holiday apartments in close proximity to the family house. The plot poses an extreme challenge: it is not a building site in the usual sense, rather it can be described as a slope edge between two access roads. On the other hand, the location offers a beautiful, breathtaking view of the picturesque world of the Pfänder mountain ridge. It is almost unnecessary to mention that this place is located in an oasis of absolute tranquility and can be described as "pure idyll." To explain the building challenge once again: the height difference along the length of the family house exceeds 6 meters. The family commissioned architect Juri Troy to process the design, who has already proven in numerous projects how unconventional yet optimal solutions can be achieved with difficult-to-develop plots.
As a native of Vorarlberg, the architect knows the Bregenzerwald landscape very well. The explicit aim of the building family was to construct a house with the lowest possible CO2 emissions. Consideration was to be given not only to the energy consumption of the house but also to the energy costs (i.e., CO2 emissions) associated with the production of building materials, including transport. Architect Troy also has extensive experience in this area, and the established goal of a holistic approach completely corresponds to his approach to sustainability in construction.

Architectural Concept
After intensive discussions with the family, the architect developed an alternative solution concept. Instead of occupying the entire plot with two separate buildings that would still somehow need to be structurally connected, architect Troy was convinced that it was more appropriate to merge both requirements into one compact building volume – that is, housing for the family and holiday apartments for guests. Juri Troy is known for the sensitive integration of his buildings into the landscape. From the height difference and two access roads, the designer made a virtue of necessity. He proposed a four-story building. At the height of the upper access road is the ground floor (level zero) with an entrance to the private living area of the Fink family, which is divided into two uppermost levels. The staircase serves as the central core of the house, around which the living rooms are arranged.
The lower access road forms the entrance for the holiday apartments right above it – also accessible from the ground floor and barrier-free. Thus, the private living area of the family and the holiday apartments are connected – yet separate. The size, shape of the roof, and materials used are inspired by the pattern of a traditional multifunctional forest house. The architect borrowed the shape of the building and roof, as well as the proportions, especially from the old rectory in Sulzberg.



The volume of the Fink house integrates into the slope and simultaneously orients itself according to the shape of the plot. Thus, a contemporarily interpreted “forest house” (Wälderhaus) was created.

The northeastern and southeastern sides present themselves externally as rather closed, but thanks to the intelligent design, are wonderfully illuminated. Here, the wooden shingle façade is particularly effective. This traditional wall cladding creates a charming, compelling contrast to the contemporary, sculptural shape of the building. A generous opening on the western side establishes a thoughtfully strong connection to the outer space. Large sliding doors offer extraordinary views into the mountain world and create a smooth transition between interior and exterior.

This part of the living area was intentionally created as a "warm space" by agreement with the family so that the family could enjoy it all year round. All three holiday apartments provide a retreat with recessed balconies and are also formally well integrated into the façade. Orientation to daylight and a strong relationship with the outdoors were fundamental parameters during the design of the building from the outset. It was a clear goal that all living rooms be sufficiently supplied with daylight – even on gloomy days.

Architect Juri Troy selected a suitably coordinated combination of thoughtfully set vertical window elements and light flowing from above to illuminate the depth of the space. Light thus enters the living space from three cardinal directions and additionally through precisely set roof windows. This strategic use of zenith light (= overhead light that is three times more intense than sidelights on cloudy days) creates a high quality of daylight that continues into the access area on the ground floor.

Daylight Evaluation was conducted using the “VELUX Daylight Visualizer” software
The evaluation of the daylight share indicates an average value of 5.6% in the living area. On average (i.e., in more than 50% of the area), the daylight share is even a remarkable 5.4%. Even the sleeping area, children's rooms, and bathroom are well supplied with natural light with an average daylight share of 2% and 4%. It sounds quite modest, but in reality, the share is exceptionally high: the Austrian standard DIN 5034-4 recommends a daylight share of at least 0.95% in the center of the room. Also remarkable about this project is the uniformity of lighting, making the space subjectively appear even brighter.



Ventilation Concept
Numerous considerations led to an unconventional ventilation concept: The three holiday apartments at level -1 are equipped with mechanical ventilation for the living area. This ensures ventilation independent of the user and guarantees a quality indoor air environment. For the private zone, the Finks decided, in agreement with the architect, on natural ventilation through windows as needed. The windows, perfectly arranged for this ventilation concept, utilize the so-called “chimney effect” and thus ensure quick and controlled air exchange.

As needed and automated – yet simple, robust, and effective: “low tech”
In the heating and transitional periods, CO2 concentration sensors (located in several zones) signal to the electrically controlled windows when they should automatically open. Thus, the individual zones are ventilated simply during the cold season, as recommended by renowned hygiene researcher Dipl. Ing. Peter Tappler from IBO Innenraumanalytik: ventilating too little (which would mean wasting valuable heating energy, and also result in extremely dry indoor air) and not least (for hygienic and health reasons) – according to needs.

Natural Ventilative Cooling
In the hot summer, the CO2 concentration sensors simply switch off, and ventilation switches to natural ventilation cooling mode ("Ventilative Cooling"). A simple physical principle is utilized: night cooling through targeted ventilation. Regardless of residents' presence, the windows automatically open late in the evening using an integrated timer and remain open until early morning hours. Afterward, the windows close automatically. With natural ventilative cooling, the building parts heated during the day cool down at night. This targeted ventilation through windows incurs practically no energy costs and thus represents a passive cooling system. Natural ventilative cooling, combined with effective external shading, forms a perfect strategy to ensure a balanced and pleasant temperature during the summer.

First Experiences of the Residents of the House on the Slope of the Mountain
The quality of indoor air can also be maintained in the sleeping area at a CO2 concentration max. 1,000 ppm. According to the definition of the relevant Austrian standard ÖNORM EN 13779, this corresponds to "special to high quality indoor air." In practice, this means that in the cold season, for example, the windows automatically open 2 to 3 times at night for a few minutes.

Even in the record summer of 2015, it was possible – not least thanks to ventilative cooling – to maintain room temperatures at a pleasant level. The residents have responded very well to this alternative ventilation system, as they can intervene according to subjective feeling at any time using the remote control to open or close the windows.

Energy
Last but not least, through the collaboration of the ambitious family-builders and the experienced, committed designer, a consistently sustainable, innovative energy concept was achieved: covering all energy consumption – including the holiday apartments – is ensured exclusively by renewable energy sources. Thanks to the highly thermally insulated envelop of the building, the compact building volume, and targeted utilization of solar gains through windows, consumption has been minimized – without compromising health and comfort. Heat is distributed via a low-temperature underfloor system. Additionally, the living area can be heated very comfortably with a stove – using wood from their own forest. The heating of domestic hot water can be predominantly covered by 15 m² of thermal collectors. The rooms are heated using district heat from the local biomass heating plant in Sulzberg, which also provides heating for the remaining hot water needs.
112 m² of photovoltaic modules generate so much electricity that, especially in the summer months, despite "full occupancy" of the building, a surplus is even produced.

The fact that the utilization of renewable energy sources and energy efficiency do not have to mean a compromise regarding building culture is demonstrated by architect Juri Troy with his "energy roof": thanks to optimal orientation, flat roof windows ensure passive solar gains; between them, solar collectors are arranged for hot water preparation and around them, photovoltaic modules for electricity generation as active components – formally summarized into a unity that harmoniously integrates as a dark roof surface into the building volume.
Despite the intensive use of holiday apartments for most of the year, the house can cover the household’s electricity consumption, auxiliary power for pumps, and also the hot water consumption almost completely through the self-generated electricity on the roof. The consistent use of daylight and particularly energy-efficient LED lights of the new generation creates a comprehensive energy concept.

Thermal Protection During Summer
Effective external shading protects against excessive overheating in hot summers. However, the rooms should not be completely darkened during this period, but still provide adequate daylight illumination. Roof windows on the southern side are equipped with transparent, electrically operated awnings, which are programmed to automatically retract in the hot summer early in the morning. Also, critical windows on the western side of the façade are protected by transparent textile shading. Targeted nighttime ventilation through the "Natural Ventilative Cooling" system significantly cools the building components heated during the day at night and is thus an essential part of the concept to ensure thermal comfort in summer (see page 14).

Environment
The project "house on the slope of the mountain" integrates harmoniously into the landscape as a contemporaneous interpretation of a multifunctional "forest house." Also in the interior, the analogy of the traditional house in Bregenzerwald continues: floors, walls, and furniture are made of solid wood.

Materials and Ecology
A clear, strict concept was pursued here: a house completely made of wood; from materials and with construction details that have proven themselves for decades in the harsh alpine climate at an altitude of 1,000 m above sea level. The basic structure of the building is made of solid wood. Both the walls and the roof construction are made of cross-laminated timber. To build such a structure in this form from solid wood requires an incredibly high amount of know-how – both in design and implementation. Wood insulation boards were used as external insulation for the walls and roof. The façade is ventilated from the back and clad with split spruce shingles. The sloping roof is also constructed according to the same principle. The chosen construction provides not only an absolutely unique solution in terms of building physics: it also ensures durability, maintenance-free operation for a long period, and moreover, each individual layer can be disassembled again if necessary. This guarantees at the end of the life cycle the possibility of disposal according to different types or even recycling. In general, great emphasis was placed on using exclusively regionally available materials, recyclable and close to nature.

As interior cladding, solid wood panels in spruce, treated with white oil glaze to prevent the wood from yellowing and give it an elegant touch, were used where necessary for the solid wood structure. In combination with a durable oak parquet floor and furniture designed by Juri Troy, a calm, harmonious, and overall benefic impression is created. The tactile perception of solid wood also contributes to a pleasant feeling. The materials, largely natural, also contribute to a good indoor climate by containing almost no harmful substances and acting as moisture regulation.
The wood for the shingles, construction wood, and wood for the panels was brought by the builders from their own forestry in the nearby Allgäu and the Bregenzerwald. All craftsmen involved in the construction came from within a 30 km radius. This is social sustainability that consciously applies in practice by creating value in the region.