Paper presented at the XXXIII IAHS World Congress on Housing, 27-30 September 2005,"Transforming Housing Environments through Design", University of Pretoria.
A major factor in the ecological sustainability of housing is the considerable amount of energy consumption, which is necessary to run the housing estates when in use, related to (central) heating, air conditioning, water heating, lighting, ventilation, lifts and other technical services. It should be kept in mind that the energy demand is heavily affected by user dependent influences. In projects, which are aimed at reducing energy demand by specific (heating, cooling or lighting) systems, detailed research should be done, taking all variables in consideration including the expected lifetime of the systems (which is in general shorter than the lifetime of the building). In ‘day-to-day’ housing development projects, however, a less detailed approach might be favourable. In these projects the approach of the energy problem comprises optimizing lay-out and orientation characteristics of the building, the physical performances of available building components (e.g. insulation performances of walls and windows) and the service systems as the industry is offering them. In designing a residential building with its systems, it may even be wise to overlook the impact of the behaviour of a specific client or target group, as the useful life of the building usually exceeds the occupancy time of that client or target group. On top of that, especially if the emphasis is on improving the energy efficiency in the existing housing stock, the reduction of energy usage should be weighed against the ecological impact of the measures for improvement. One of the methods designed to support decision-making in this field is the method of the Eco-costs/Value Ratio (EVR). In “Cost effectiveness of sustainable housing investments”  this method is elaborated in a way that it can be used as a tool in housing development projects concerning both new construction and renovation. The paper will show how architects can use the EVR method in housing (re)development projects to weigh the ecological impact of renovation or new construction activities against the ecological profits of improved energy efficiency.
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