Powerhouse Brattørkaia in Trondheim is by far the largest powerhouse project in Norway to date. The surrounding harbour area close to the city centre is currently undergoing a radical change: several office buildings, hotels and a speedboat terminal have been built in recent years. The energy ambitions of Snøhetta's nine-storey office and commercial building become apparent at first glance. Its trapezoidal floor plan with four convexly curved facades is designed for maximum compactness, and the inclination of the sloping roof is positioned to achieve the highest possible solar gains. An oval inner courtyard provides additional daylight for the seven uppermost levels. With the exception of the north-western elevation, all external facades are clad with black, crystalline high-performance photovoltaic modules. The roof is also used almost entirely for solar power generation. Only the areas along the oblique roof edges, as well as the north-west facade, are clad with aluminium composite panels. The inner courtyard, on the other hand, presents a completely different picture, with the parapets clad in gold corrugated aluminium sheeting. The architects also differentiated the solar shading according to location and direction: The windows on the south, west and east sides were fitted with external shading blinds, those on the north-west facade with internal solar shading and those around the inner courtyard do not have additional shading devices but were fitted with solar control glazing on the upper floors.
On the ground floor, the client opted for a mix of uses with a high public impact. In addition to the reception area for the office levels, there is also a café, an auditorium and a showroom that communicates the functionality of a plus-energy building to interested parties. An external staircase along the western facade leads passers-by into the inner courtyard and onto a pedestrian bridge that connects the new building directly with Trondheim's main railway station.
A concrete mix developed especially for the new building, in which Portland cement was replaced by fly ash, contributes to the ecological optimisation of the building structure. The 3000 m² photovoltaic modules supply around 450 MWh of electricity annually. Heating is supplied by a heat pump with 254 kW thermal output, which uses the water of the harbour basin as a heat source. In summer, excess heat from the building is transferred directly to the harbour water via a heat exchanger, but without mechanical cooling. Heat and cold are transferred to the interior via the ventilation system. The acoustic ceilings on the office levels are designed in such a way that large parts of the concrete structure are exposed to the inside air and act as a thermal buffer against temperature fluctuations.
In order to minimise heating consumption, the Powerhouse forms a network with the adjacent older office building. The heat pump initially supplies the radiators installed in the neighbouring structure with heat. Their return temperature is still sufficient to heat the plus-energy building. In summer, on the other hand, each building has its own cooling circuit - because the water from the North Sea is available in sufficient quantity to be able to dispense with additional synergies in cooling the building.
