This experimental plus-energy building was the overall winner at the 2017 U.S. Solar Decathlon in Denver. Beyond being useable as a private home, the NeighborHub was conceived as a ‘house for neighbourhood living’. The student team chose seven themes, such as energy, waste management, biodiversity, mobility and food, that guided the entire project.
From May 2018 onwards, the building will find a permanent location in Fribourg, Switzerland, on a former brewery site that is now used as an innovation district and research centre. Here the NeighborHub will serve as a place for discussion as well as a demonstrator of future technologies.
The climate concept of the house differentiates between a thermally controlled core and an ‘extended skin’ along the perimeter, which is neither actively heated nor cooled and where indoor temperatures thus fluctuate. The latter is shielded against the outside world by translucent polycarbonate and transparent acrylic panels for passive solar gain and natural light, as well as opaque facade modules for active solar technology, both thermal and photovoltaic. The majority of the facade can be folded upwards so that the NeighborHub opens out entirely to its environment. Even when it is closed, the transparent panels provide views outside, and four fully glazed sliding doors also allow daylight to penetrate into the building’s core.
Three modular skylights with semi-automated shading – two for the core and one row of modules for the perimeter area – provide the indoor spaces with additional daylight and support the natural ventilation. The electric light is dimmable and equipped with variable colour control in order to help the users maintain a natural sleep/wake cycle.
All entries to the Solar Decathlon are evaluated in ten categories, six of which rely on qualitative and four on quantitative criteria. To earn full points on the ‘Health and Comfort’ category, teams must maintain temperatures between 20°C and 23.3°C, relative humidity between 35% and 60%, indoor CO2 levels below 1,000 ppm, and provide the building with an airtight envelope.
The NeighborHub is equipped with wireless sensors that keep track of the indoor climate. A weather station also monitors the outdoor climate and provides forecasts of solar irradiation, wind and rain.
Once the building is operational in Fribourg, the monitoring will resume, with the results being used to refine the control algorithms for the ventilation, heating, cooling and solar shading.
Alongside the overall Solar Decathlon competition, the NeighborHub also won first prize in six of the ten categories. Of particular interest were the full (100/100) points in both the engineering and the architecture contest. Another first place was achieved in the Health and Comfort category, with 97.165 out of 100 points. Temperatures and CO2 levels only rose above the maximum permissible limits in a few rare instances. Results were somewhat more mixed in terms of humidity, with values below 20% reached on two of the eight days of the evaluation. Although the control systems in the house prioritise passive strategies over active heating and cooling, the tight constraints of the competition rules in terms of indoor temperatures meant that a cooling unit had to be installed in the house. When the building enters into permanent operation in Fribourg, the thermal requirements will be less strict. The student team thus hopes that there will be less need for active cooling and the passive design of the perimeter area can be used to a greater degree to ensure a stable indoor climate.