The two lowest levels, accommodating the citizen’s service centre, conference rooms and the registry office, are accessible to the public. The office levels above can only be accessed with a chip card and lifts or, alternatively, via the cascading stairway in the central atrium. Thanks to the adjoining open kitchenettes on each level, the atrium is the social hub of the building. Four further storeys are embedded below ground incorporating plant rooms and bicycle parking facilities for employees as well as a public underground car park for 400 cars.
Office landscape with free seating
Each department is assigned a level in the tower within which the employees can choose their work place. The interior design provides a wide range of possibilities: individual desks, team tables, lounge furniture as well as long dining tables alongside the kitchenettes. The cafeteria on the fifth floor is also a potential work place. It is the only place separated from the atrium since glass partitions had to be installed to meet fire safety and sound protection requirements. A loggia in the southern facade marks the position of the cafeteria.
A triple-storey greenhouse on the uppermost storeys is not only a tranquil contrast to the busy office space, but also a place to enjoy the panoramic view of the river Maas. The glass cube is designed as a break room, a venue for events and a system to preheat the supply air for the offices. Unfortunately, the architects’ idea of planting vegetables and herbs for the canteen here has not yet materialised.
In addition to the north-facing side of the building, greenery has also been added to parts of the west, east and south facades. The plants have been selected to take account of the different light incidence. A computer-controlled irrigation system has been integrated in the planters to supply the vegetation with water and nutrients. The town has signed a ten-year maintenance contract with the manufacturer of the system to ensure long-term functionality.
The ribbon windows and the protruding shading elements, which have been equipped with photovoltaic modules, are particularly prominent in the south, west and east facades. The brise soleil are the only exterior shading devices for the offices. However, textile screens have been fitted in the interior to regulate the incidence of daylight and to prevent glare.
Bare surfaces for better recycling
The building materials play a key role in meeting the requirements of the cradle-to-cradle concept. To facilitate the recyclability of the building materials, the interior is predominately characterised by bare, uncoated surfaces. The architects chose Belgian blue stone for the floor covering on the ground floor and strip parquet flooring and carpet tiles with a cradle-to-cradle certification for the upper floor levels. The exterior walls are made of cross-laminated timber produced with dowels rather than with glue. A framework of uncoated galvanised steel sections supports the glass facade on the north-facing elevation. Acetylated wood, which is extremely durable even without being stained or sealed, has been used for the lamella ceilings on the lower floors, the greenhouse’s load-bearing structure and the window frames. The architects and the contractor even managed to replace up to 70 % of the aggregate in the structural concrete with sand and gravel. In order to close the water cycle in the building, the landscape architects have created a pond, which functions as a helophyte filter, between the two L-shaped wings on the ground floor. The waste water from the sinks, the cafeteria’s kitchen and the roofs is purified here naturally and then reused to either flush the toilets or to irrigate the green facades.
Solar energy for ventilation and electricity
The building is ventilated mechanically using two central ventilation units. One, situated in the basement, supplies the lower floors with fresh air; another in the attic level is supported by a solar chimney, which consists of dark coated sheet metal ducts incorporated in a large glass cube on the roof of the building. The sheet metal is solar heated; this causes the surrounding air to rise, thus drawing the exhaust air out of the atrium. The advantage of this method is that the air is extracted from the building without using dedicated waste air ducts or energy-intensive fans.
The primary energy demand of the building is more than 50 % lower than the specified level was in the Netherlands at the project design stage. A heat pump, which is connected to two groundwater wells, generates the energy to heat and cool the building. The underground car park, which has been equipped with thermally activated building surfaces for this purpose, functions as the second cold source. Heat or cold is distributed throughout the building via heating and cooling ceiling panels. A total of 1,000 m² of photovoltaic modules on the roof and the facades cover approximately 15 % of the building’s power demand. The remaining demand is supplied by purchasing certified green electricity. Altogether, the City of Venlo invested almost a tenth of the €35 million construction budget in sustainability and energy efficiency measures. Depending on energy price increases, it should be possible to recover the costs within the next fifteen to twenty years.
