Zero energy housing retrofit

ABSTRACT: In the face of the two key sustainability issues of global warming and depletion of non-renewable sources of energy, it has proven possible, and even relatively simple, to construct new houses that require little or no non-renewable energy for their operation. However, existing dwellings represent a much more difficult problem. The first difficulty lies in the issue of scale, for example in New Zealand about 20,000 new dwellings are constructed each year, but the existing housing stock comprises around a million units. It would take fifty years for improved new houses to replace the existing ones, and the demolition of the existing dwellings would represent a considerable waste of resources. The second difficulty is the one of technology. It is possible to apply a range of technologies to reduce the energy demand of existing buildings. These include things like increased insulation, improved window glazing, solar water heating, improved lights and low energy appliances. The installation of some of these technologies, particularly those that involve alterations to he building fabric, can be very disruptive in an existing occupied home. In the light of these difficulties, the paper will discuss an alternative approach to achieving the zero energy retrofit of an existing house in New Zealand through the use of a roof-mounted photovoltaic system combined with non-invasive energy improvements. The paper gives detailed costings and measured performance data for the installation and will attempt to draw some policy conclusions