This study showed the variation in carbon footprint size a standard house design can have depending on location and the amount and type of energy it expends on heating during its operational life. This study can be expanded using the HEEP information on New Zealand home heating practice to ascertain the carbon footprint of new housing stock throughout the country. This information could be used assist the decisions of policy makers and planners considering the environmental impact of new housing and monitoring change in the urban landscape.
The carbon footprint of the increase in home insulation levels in New Zealand shows that the new legislation has achieved the aim to help comply with international obligations to lower carbon emissions by reducing electrical heat energy demand for the long term. Savings in heat energy demand reached government expectations of 30%. This was achieved with a design which failed to reach the target BPI set by the
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Building Code. The heat savings recorded support the cause for additional thermal insulation to save heat energy.
The sensitivity analysis conducted in this study shows that as carbon emissions fall through the reduction of non-renewable energy sources for electricity generation, so does the rate of environmental payback for the embodied energy in our homes. In Zone 1 the payback period for the standard design house using HS2 was 156 years, which is more than three times the design life. For Zone 2 the payback was 82 years, for Zone 3, 59 years. This should be of concern to the Government and the building energy community at large, as a long payback period undermines the strategy to reduce the environmental impact of the New Zealand housing stock by increasing thermal requirements. This result is reflective of Mithraratne and Vale‟s (2004) study in which the concrete version of their standard house design could not recoup the additional embodied energy by thermal gains through high mass over a 100 year design life. The next step forward is to reduce embodied energy levels within new construction and to look to more efficient or alternative sources of home heating.
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