Housing association De Woonschakel builds 24 energy-neutral apartments with Rockzero® Building Systems in demolition and new construction project in Bovenkarspel

The West Frisian housing association De Woonschakel from Medemblik is building 24 new energy-neutral apartments for the social housing sector in Bovenkarspel. These are being realized using a new construction technique. This is a demolition and new construction project in which the apartments are being built on existing foundations. Architectural firm TBE-ZA from Volendam produced the design which uses ROCKWOOL®'s innovative Rockzero Bouwsystemen, which in terms of its high insulation value, light weight and flexible dimensions proves to be an ideal structure for an existing foundation. The apartment complex will be completed in the first quarter of 2020.

Ton Boukens is De Woonschakel's project manager on this demolition and new construction project in Bovenkarspel. "On the site of the new apartment complex there were first two-story apartments from the 1960s, ground-floor apartments with a porch entrance," Boukens says. "The complex no longer met current housing requirements. It was not fireproof, poorly insulated and the building's installation was completely outdated." Working as a team with the architect, housing corporation and contractor, the decision was made to demolish the old homes and build the new apartment complex on the existing foundations. "To insulate the shell and the gable roof as best as possible, the lightweight building system Rockzero was chosen," says Boukens. This is a load-bearing, modular and circular system made entirely of rock wool. Thanks to its high degree of flexibility, the building system allows buildings to be dismantled and rebuilt in another location. ROCKWOOL stone wool is also fully recyclable, retaining its original quality. The roof has no tiles, but consists entirely of a solar roof with pv panels to supply electricity to the homes. "The solar panels already provide a huge output of electricity, but the homes will also be connected to the power grid," Boukens said. In this project, the housing corporation did not opt for heat pumps. "Because the homes are extremely well insulated, each home will have infrared heating panels, which will be fixed to the ceiling of the living room. Hot tap water comes from an electric water heater. The homes can easily achieve zero-to-the-meter, but it depends very much on the residents how much electricity they need," Boukens explained.

Stabo Bouw from Blokker is involved in this project as the construction company. Ton Stavenuiter, director of Stabo Bouw, explains that the choice of this building system was based on a number of crucial aspects. "The shell had to be replaced in order to properly insulate the homes. This also required building on an existing foundation." Fairly quickly, the construction team decided that Rockzero would be the best solution for this. The system is certainly 50% lighter than traditional building systems and has exceptionally high insulation values (RC value is 8 m2.K/W), provides excellent acoustic performance and is at least sixty minutes fire resistant, meeting the highest fire safety requirements. Stephen Muller, Rockzero sales manager at ROCKWOOL B.V., has been closely involved in the preparations and implementation of the new apartments. "The Rockzero building system from ROCKWOOL stone wool lends itself extremely well to the rapid construction of facades and roofs, which means a significant reduction in construction costs and fast, smart construction of homes," says Muller. "The walls of the homes are prefabricated in our workshop so that a home can be built quickly on site," adds Stavenuiter. "Throughout the construction process, we constantly pull together with people from ROCKWOOL and think together about how we can make the next project even faster and smarter. We think along in specific solutions, for example about stability or sound insulation, in order to optimize the building system further and further." Stavenuiter indicates that the light weight and flexibility of the superstructure system are strong pluses for building on an existing foundation. "You don't have to go into the neighborhood with heavy equipment because of this. Also, with this construction system, a cascade house is quickly built, requiring relatively little manpower, such as scaffold builders combined with masons, anymore. Waste is also kept to a minimum. Furthermore, the facades were finished flush on the inside and wall sockets were installed. In addition, on the next project, we also want to factory install the exterior frames."

Ewoud Blok, project architect at TBE-ZA Architects & Engineers of Volendam, designed the apartment complex. Rebuilding on an existing foundation is very interesting in terms of legislation and procedures because it often stays within an existing zoning plan. "Permits are then arranged more quickly. The municipality checks the zoning plan, which the building plan therefore often already complies with," Blok said. For him, the architectural challenge lies mainly in designing new floor plans within the existing contours of the building. "The houses will have a different layout and the indoor staircases will be placed on the outside. This creates more space and uses it more efficiently," Blok said. The installations will have a place in the attic, which consists of one large technical room accessible from the side. "The Woonschakel remains the owner of the attic floor and is the only party with free access for maintenance." Blok is paying close attention to the look and construction of the complex. "For the design of the new apartment complex, we chose the right facades, with suitable daylighting and access, that match the existing homes in the neighborhood," Blok said. The facades have a warm appearance. For this, Rockpanel® cladding is used, which is also made from stone wool. This cladding fits seamlessly with the Rockzero building system. "For the facades of the new apartment complex, we chose horizontal strips in a warm terracotta color, combined with gray accents," Blok adds. "In this way, we have ensured that the apartment complex has been realized with a special system that at the same time has a warm and durable appearance that fits into this 1960s neighborhood," says Blok.

The apartment complex will be completed in quarter 1, 2020.

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