Introduction

Signs of stress in materials supply are all over, from copper robbers arrested in Western countries, to closed down construction sites due to a lack of cement. When we will have reached the limits of resources, is under discussion, but there is hardly any discussion on the fact that , with business as usual and growing world population, there are limits. After experimenting a 100 years since the Industrial revolution, construction, consuming around 40 pct of all resources, is in need of a new approach, one that operates in a closed cycled manner, to be able to secure resource supply for our built environment, for maintenance and adaptation.

Since the earth has no spare materials sources outside its own system ( like energy has), the model should be purely based on available resources, and their continuous use over time. Time is here the crucial element, the time resources need to recover from their use, to avoid further depletion of stock Rather then a cradle to cradle approach of products, this requires a resource model based on a closed loop provisioning of functions, in our case: providing shelter.

In this section closed cycle management is analysed for its merites, and a model for the building and construction world has been developed. A ,model that begins and starts with the available existing buildings, as the valuable human stock, the habitat so to say, and to see this as the continuous organism that needs to be maintained, and growth supported, in a highly efficient way, when it comes to adding new buildings, materials on one side and demolishing or dismantling on the other side. In further analysing this model, the different parts are detailed, one section being "adding new constructions" and another section stock level management. The last one is developed at Wageningen university and called Urban Harvest.