The Green Roof



Het Groene Dak (The Green Roof) is an ecological housing project in Utrecht (Netherlands), consisting of forty rentals and twenty-six privately owned houses. The residents themselves initiated the construction of the project. In 1989 they founded an association with the following goals:

  1. The realisation of a housing project founded on principles of ecological construction and lifestyle.
  2. Maximising the influence of the future residents on the realisation of the housing project, both during the design phase and during construction.
  3. The realisation of homes for low-income residents.
  4. The realisation of homes for households other than the traditional family.
  5. The realisation of workplaces close to homes.


In 1993 the housing project was completed and it can safely be said that the association has reached most of its goals. Due to the active participation of the residents the housing project is fairly ecological, has a large variety in types of homes for a project of its size and has al large proportion of low-income homes. Because of a lack in demand from the residents, workplaces have not been built.

In terms of ecology, the focus has been put on the usage of sound construction materials and the conservation of energy and water. Furthermore, a large inner garden has been created by altering the division of lots in the original urban-planing design. With regard to construction materials the use of tropical hardwoods, PVC, CFH-containing isolation foams and concrete has been minimised. To reduce the energy demand of the homes, they have been build with extra insulation and facing the south, have low-emittence double glazing and high-yield furnaces. Some homes have hot-fill washing machines and hotwater boilers, which operate on solar power.

In order to conserve water, measures have been taken both to reduce the usage of tapwater and to replace the sewage system. Conservation of tapwater is firstly achieved by conscientious behaviour of residents. Secondly it is achieved through the installation of watersaving taps, showerheads and toilets. These last few measures are independent of resident behaviour. Furthermore, there are installations for the utilisation of rainwater in washingmachines and toilets. Independence of the municipal sewagesystem (an experiment in ten homes) is achieved by using compost toilets and wastewater treatment systems. Especially these wastewater treatment systems, and also the compost toilets, require al large amount of dedication from the users. But given the dedication, the environmental yield of these measures is large.

At present the association takes care of the communal inner garden and runs a community centre, built in the inner garden under direct management of the association itself. In the construction of this community centre experimental use has been made of straw-earth building techniques and the building is topped with a grass roof. After a year and a half of residence, large savings in water, fuel and electricity have already been established.

Michel Post and Guusje van Adrichem.