Robust scientific projections show that climate change will significantly affect the New Zealand built environment. Major impacts are expected from inland and coastal flooding, building overheating, and increased occurrence of droughts and fire risk in the eastern parts of the country. It is essential that the climate-change planning process starts now, given the longevity of housing developments and infrastructure in increasingly at-risk communities. Costs to homeowners and the national economy, and social disruption and tension, can all be avoided by developing and retrofitting with consideration of increasing climate exposure and vulnerability.
The inventory of the building stock suggests that climate change adaptation should focus on residential, institutional and commercial buildings. Industrial-type buildings can largely be ignored for climate change adaptation as they are usually fairly short-lived and simple buildings.
Social impacts from climate change will be intertwined with other major social changes. A more detailed analysis of social impacts suggests these will be powerfully shaped by dynamics of social inclusion and exclusion. The prospect of increased damage means many communities may need to re-assess their futures. The social research, involving a broad range of experts from outside the building sector, warns that significant social disruption and conflict over changes in the value of land in coastal areas will occur, especially where wealthy enclaves suffer significant loss in value. The relatively mild impacts of climate change in New Zealand compared to other countries are likely to be a key driver of immigration. As climate change drives immigration, it also indirectly drives growth in the housing sector.
Building overheating from increase in frequency and severity of summer temperature extremes can be avoided by passive design and retrofit. Thermal simulations show that comfortable indoor summer temperatures can be maintained in all climate change scenarios explored by adapting to overheating with window shading and natural ventilation. The simulations also show significant year-round energy savings in all buildings using double-glazing or high-performance glazing, and improved ceiling and wall insulation.
To maximise economic benefits insulation retrofitting of the existing housing stock should be done as soon as possible. Thermal insulation comes out the most favourable as currently we under-insulate our homes by a huge amount. The second most favourable retrofit is upgrade from single-glazing to double-glazing. While awnings provide good sun protection, in no situation do they provide a greater NPV than having no awnings. It is therefore not recommended that awnings be installed if the primary objective is lower NPV.
- Climate Change Impacts in New Zealand: A Cross-Disciplinary Assessment of the Need to Adapt Buildings, with Focus on Housing, awarded best paper at SB07 Sustainable Building Conference, by Jonas Bengtsson, Jessica Bennett, Stephen McKernon, Brett Mullan and Ian Page, November 2007.