passiv solar

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passive Solar
An intervention of Walter Kaufmann and Hermann Unterrainer

Daniela Brighi and John Stone

In the town of Zwischenwasser (A) the small (very small) community Dafins has over time built a strong and warm participation of citizens in political choices of the administration and management, supported in the difficult task of countering the process of centralization of services that tend to concentrate in larger agglomerations. It is a process that did gradually disappear education buildings, commerce and services to the public.
Thus, maintaining strong unit, residents have first wanted the kindergarten and the four classes of elementary school, then are organizing themselves to bring the primary shops have already organized an efficient public transport with buses at times conformed to their needs.
On a more strictly ecological profile, to counter pollution they have decided to support local people who want to adopt photovoltaic roofs. All architectural choices, including precisely those relating to the school building, are ​​public, commented on, discussed and accepted. Under an urbanistic profile compact volumes mark the edge of the road.
The decision to place a village of only four hundred souls’s new school directly on the road rather than retreating the building with a courtyard, has long been debated.
At the end prevailed the desire to use the public volumes to contribute to the area’s design, in order to maintain an overall compact image on the two sides of the road, while keeping free the slope towards the valley.
The thick insulation and distribution on the street side of the service areas ensures total insulation compared to the small traffic, but the courtyard opens to a breathtaking view over the Rhine’s valley.
The building, completed in 1990, consists in two connected parts and contains two classrooms, a nursery, a gym and a workshop for woodworking.
At that time the use of alternative energy was not so widespread and so initially it was thought not to do so, however, soon emerged that the chosen orientation and the project’s compactness were favorable to such considerations.
The main block, oriented on an east/west axis, consists of a light heavily insulated wooden frame, while the gym, with the playing surface partially buried, is made with reinforced concrete. The two sides, main building and gym, contrast on what concerns energy systems, construction methods and interior climate.
The semi-buried gym does not have autonomous heat-captation but uptakes his power by solar energy taken from the main body. This one turns to the sun with a system of window openings for the passive use of the sun and is equipped with solar air collectors. These absorbers are installed on the south wall and roof of the building: behind the glass surface is placed a suitable corrugated black to absorb solar heat, the air between the plate and the glass heats up, it rises up the ridge of the roof, and from there a fan conveys it through a conduit in an accumulation of stones of medium size, placed in the building’s basement.
This simple closed loop allows to store heat for several days and special sensors monitor potential overheating and real needs of the system. The sizing of the storage tank is designed to cover the full heating requirements during three days of overcast sky.
If bad weather conditions should protract, making the passive insufficient, a normal oil boiler starts always through sensors, that integrates the air temperature.
A second closed loop carries the hot air through a fan from the cavities of the accumulation to floors and walls. It is nine hypocaust pipelines, which form the only heat distribution system. A control unit controls air temperature and speed in accordance with the needs.
Each room has a manual adjusting device which determines the opening or closing of the single hypocaust.
A heat exchanger located between the collector and the accumulation, pre-heats the domestic water, then brought to the desired temperature by means of an electric boiler. Among the public buildings of Vorarlberg was one of the first to use such a high percentage of solar energy for its heating. The town of Zwischenwasser was awarded for the best solar architecture, thanks to this school. The corridor and distribution spaces places north are not directly heated but undergo the irradiation coming from the walls in common with the classrooms; to contain the dispersions are kept at a temperature lower than the classrooms, have a higher isolation and lower surfaces windowed.
Even the gym has a design temperature of 18 °, achieved with the system to hypocaust place in the roof slab. The working space and storage areas of the gym are not heated, but being placed in the basement does not undergo large changes in temperature.
In summer to avoid overheating, a simple mechanical device can be opened for ventilation of the attic soffit located on the first floor in the porch to the south, allowing the entry of fresh air in the cavities of the outer walls up to ventilandole ridge where other aeration grids expel air heated by the passage in the walls. This determines a chimney effect that draws fresh air from underpass other. Blackout curtains and blinds outdoor classrooms for modulating the intensity of light and heat coming through the large windows. For areas to the north is a color was chosen “ox blood” that, while not typical color of the area, had to tackle the technological image of the south facade. The wall on the road bends slightly to follow faithfully the profile of the road, giving harmony to the building and frequently breaking the rigidity of the architectural schemes of the new construction of Vorarlberg.