Comparing environmental impacts of renovated housing stock with new construction

When undertaking urban renewal projects, decisions must be made between housing maintenance with some minor interventions, and total housing redevelopment entailing the demolition of the existing stock and replacement with new houses. Simple renovations are only possible if the quality of the existing dwelling is sufficient to fulfil current needs. In most urban renewal districts in the Netherlands the existing stock does not meet these current needs. That is why large-scale demolition and the construction of new dwellings are undertaken. However, renovation-based strategies could offer more sustainable alternatives. A comparison of the environmental impacts is made between the renewal options of maintenance, consolidation, transformation, and redevelopment for two typical cases of Dutch urban renewal. The environmental effects are calculated using the Life Cycle Assessment method. Results are presented according to the following environmental effects: the quantities of material, the energy and water used, waste, and environmental impacts. The use of environmental impacts gives a more complete picture than the use of quantities. The transformation of the existing housing stock is found to be a much more environmentally efficient way to achieve the same result than are demolition and rebuilding. The embodied and operational energy use is also compared. Due to the relatively short lifetime of post-war dwellings, the embodied energy can amount to 30% of the total energy use. This means that it is worth using construction methods that reduce embodied energy and designing new buildings so that they are flexible.