Energy House Deltawind/

The Deltawind Cooperative was established in 1989 on the initiative of the island residents of Goeree Overflakkee, in the south of South Holland. They wanted to generate their own energy and, in August 1989, founded the Deltawind Cooperative. They started with a few small wind turbines for collective energy supply.

Today, Deltawind is an energy cooperative with 2,500 members and several wind farms, all located on and owned by the island. Over the years, Deltawind has increasingly developed into a social organisation, where energy, sustainability, and the well-being of the people of Goeree play an important role. For example, an energy advice centre has been set up to help residents make their homes more sustainable, and social initiatives are supported, such as assisting people who are distanced from the labour market.

For this social role, an office was also needed to provide space for these initiatives. It had to be a true ‘clubhouse’, where, in addition to permanent employees, Deltawind members and occasionally other organisations could have a place to work, hold meetings, or give presentations.

A location for the new building was chosen at the entrance to Oude Tonge, on the edge of an industrial estate. The site was larger than strictly necessary for the building volume, but it was also poor in terms of water quantity, water quality, and biodiversity. The initial idea was to enrich the ecosystem of the site—to create as much biodiversity as possible while improving water quality and supply, maximising the green footprint of the site.

The first intervention was to minimise the building’s footprint. By elevating the structure, the landscape could flow beneath it, creating niches for plants and animals. Additionally, nature-friendly banks were designed along the existing poor-quality drainage ditches, and several water basins were excavated. The soil extracted from these basins was used to create mounds under and around the building, further enhancing microclimates and ecosystems.

As a result, the building is raised on stilts above ground level and positioned as a long, narrow, tall volume along the edge of the site. This also acts as a visual barrier to the less attractive industrial area behind it.

We sought an internal dimension within the structure that would allow a long worktable to be placed, with seating on both sides and enough space to walk around comfortably. A depth of 4 metres proved effective for this purpose. This forms the large open space in the centre, functioning as an open workspace. All other functions—such as toilets, storage, stairwells, and quiet workspaces—are arranged as separate rooms along the street-facing side, resulting in a staggered northern façade.

On the southern façade, a 1.5-metre-deep greenhouse extends along the entire length and height of the building. This greenhouse, with its plants, serves as a climate façade. In autumn, winter, and spring, solar heat from the greenhouse is used to warm the building. The ventilation system also utilises air from the greenhouse, with the plants filtering fine dust from the air—sometimes even allowing the scent of flowers to be noticeable indoors. This reduces the need for heating capacity, allowing a relatively small climate system, in the form of an air-to-water heat pump, to suffice.

The building is net energy-positive, as the entire southern side of the roof is fitted with 72 photovoltaic panels. Any excess energy can be stored in a battery in one of the basements or in one of the electric cars, which are connected to a smart grid with bidirectional charging stations.

A skylight runs the entire length of the building, allowing light to penetrate downwards through voids. On the ground floor, a long table extends across the entire length, providing a communal workspace. Additionally, there are quiet workspaces, train-style seating areas, and meeting rooms. At the end of the building, the kitchen and canteen are located. The staircase there can be extended to create a small auditorium for 40 people.

Various types of wood have been used throughout, each chosen for its functional qualities. The columns of the substructure are made of azobé wood due to its strength and high durability class, while the main supporting structure consists of laminated spruce. The floors and entrance area, which require stability, are made of cross-laminated timber (CLT), and the timber-frame walls feature an interior layer of multiplan panels. The exterior façades are clad with the outer shells of repurposed azobé mooring posts. The façade within the greenhouse, which experiences less wear, is clad in larch sourced from forests managed by Staatsbosbeheer. To avoid painting, the window frames are made of thermally treated fraké wood.

Inside, all wooden elements are spruce, except for components requiring greater hardness, such as balustrades, stair nosings, and handrails, which are made of beech.

The façade and roof incorporate various provisions for birds and bats. A barn owl box is built into the gable end, which was already inhabited before the building’s completion. Additionally, there are integrated sparrow and tit nesting boxes, as well as bat colony boxes. Together with the surrounding garden, the building contributes to a positive green footprint for the site.

• Client: Coöperatie Deltawind, Oude Tonge
• Architect: RO&AD Architecten, Bergen op Zoom
• Structural Engineer: Summum Engineering, Rotterdam
• Contractor: Bergh Bouwsystemen, Roosendaal
• Timber Structures: Arcon, Nuenen
• Installation Consultant: Dubourgraaf, Geersdijk
• Installer: Lomans, Capelle aan den IJssel
• Interior Architect: Kinkorn, Tilburg
• Landscape Architect: Vis-a-Vis, Woudrichem
• Planting: Van Helvoirt, Goirle
• Photographer: John Lewis Marshall, Mike Bink