Passive Design

Designing the building and the spaces within it to benefit from natural light, ventilation and even temperatures.

Climate change

Buildings should be designed to use energy efficiently, and to cope with the stresses arising from a changing climate.

Buildings are indirectly responsible for around 20% of New Zealand’s energy-related greenhouse gas emissions, contributing to climate change. These emissions mostly come from using fossil fuels for heating and cooking and generating electricity for appliances and space and water heating, cooling and ventilation.

Scientists expect New Zealand’s climate to change during the rest of this century, though the impacts will vary from place to place. Changing rainfall, wind, temperature, storm and other climatic patterns will all influence building design – for example, by requiring buildings in some parts of the country to cope with stronger wind loads or more intense rainfall.

Buildings should be designed to minimise greenhouse gas emissions from energy use. Most importantly, passive design features can help to reduce energy use for heating, cooling, lighting and other activities. Over the life of a building, small gains in efficiency can add up to significant reductions in emissions.

The National Institute of Water and Atmospheric Research (NIWA) has warned that the biggest effects may be due to more extreme and more frequent weather events such as floods, droughts and storms, rather than changes in average weather conditions.

Climate changes will affect home design. When designing for climate change, designers will need to consider changes to:

  • temperature
  • rainfall
  • solar radiation and UV intensity
  • wind
  • rising sea levels
  • fire risk
  • insect pests
  • impact of emissions charges
  • changes to building/planning rules.

It is not just design of new buildings that needs to be considered. Most of the buildings that will be standing in 2050 already exist, so improving the energy efficiency of the current building stock is important.

Temperature
Ministry for the Environment projections for likely future average temperature rises are around 0.9°C by 2040 and around 2.0–2.1°C by 2090. The strongest warming is likely to be experienced in winter, and warming may be greater in eastern and northern parts of the country.

An increase in the number of days above 25°C is expected, particularly in northern locations.

If these changes occur, they may affect thermal comfort and the demand for cooling inside homes. If there is also an associated rise in humidity, there may potentially be an increase in mould and fungi growth that could in turn result in a rise in health issues.

Rainfall
The Ministry for the Environment also gives projections for likely future changes in rainfall, and in some areas this will be considerable. Hokitika is expected to see an increase in average winter rainfall of 21% by 2090; for Queenstown, the average winter rainfall is expected to increase by 29%.

Rainfall is expected to increase in southern and western areas (Taranaki, Manawatu-Wanganui, West Coast, Otago and Southland) and decrease in northern and eastern areas (Hawke’s Bay, Gisborne, eastern Marlborough and eastern Canterbury). This means that the difference between current rainfall levels between east and western areas will increase.

Extreme rainfall is expected to become more common, particularly in the south and west. This will put more pressure on stormwater and sewer systems and on roof drainage. The risk of flooding could increase, and properties in low-lying areas are likely to be at risk.

MfE estimates that West Coast winter thunderstorms could occur four times as often by the end of the century as they do now.

Summer rainfall is expected to reduce, which will put pressure on urban water supplies. More droughts are expected in areas that are already currently drought-prone.

Higher temperatures, lower summer rainfall, increased winter rainfall, increased evapo-transpiration and changes to water table levels will all change seasonal patterns of soil wetting/drying. This could increase the risk of subsidence, particularly for building foundations on clay soil or for buildings adjacent to banks or cliffs.

Solar radiation and UV intensity
UV intensity is expected to increase until 2015 and later gradually decrease by about 6–7% by 2030 and be 10% lower than current levels by 2070. UV radiation is currently a major cause of polymer degradation (for example, plastic, rubber, wood lignin).

The effects of climate change on solar radiation through changes in cloud levels or sunshine hours are uncertain.

Wind
The westerly wind flow across New Zealand is expected to increase, and it is likely there will be more stronger winds. According to one projection, the frequency of winds of 30 m/s or more may double.

The number of storms and tropical cyclones could increase, although projections are uncertain. One scenario is that the number of tropical cyclones reaching New Zealand may reduce, but those that do get here may have greater impact.

Rising sea levels
The Ministry for the Environment recommends planning for at least a 0.5 m rise in sea level and considering the consequences of at least an 0.8 m rise in sea level by the end of the 21st century relative to the 1980–1999 average.

The Intergovernmental Panel on Climate Change (IPCC) says that oceans around the world have risen around 20 cm on average since the beginning of the 20th century. The seas around New Zealand have risen in line with the global average, but could potentially rise more quickly in future. Global sea levels are likely to increase by between 0.25–0.6 m by the end of the century.

In November 2015, the Parliamentary Commissioner for the Environment released a report Preparing New Zealand for rising seas: Certainty and Uncertainty.
The report estimates that about 9,000 New Zealand homes stand less than 0.5 m above spring high tide levels. Cities with large areas that are particularly low-lying include Napier, Lower Hutt, Christchurch, and Dunedin. Dunedin has 2600 homes below this threshold. Some small towns also significantly affected: Whakatane, for example, has 276 homes in this category.

The occurrence of extreme sea level and coastal flooding events changes rapidly as mean sea levels rise, according to a 2016 Royal Society of New Zealand report. For example, with a 30 cm rise in sea level, the current ‘1 in 100 year’ extreme sea level event would be expected to occur once every year or so in many coastal regions.

Fire risk
The fire risk is expected to increase significantly by the middle of the 21st century in eastern locations because of reduced summer rainfall and increasingly dry vegetation.

Insect pests
Termites and infection-bearing pests such as mosquitoes may become more common as a result of warmer climates (although research suggests that current quarantine and timber treatment practices will be enough to keep termites away).

Reducing emissions in the building sector
The 2016 Royal Society report found that greenhouse gas emissions can be reduced in the New Zealand residential and commercial building sectors through better energy management and improved minimum performance standards for appliances. 


Emissions reductions can also result from:

  • improving insulation levels
  • retrofitting existing building stock
  • integrating renewable energy systems
  • supporting innovative ‘green building’ designs.

Changes to building/planning rules
Climate change is likely to affect building and urban planning requirements as the government and local councils seek greater energy efficiency from buildings and require that increased structure, durability and weathertightness issues are met in the face of more extreme weather events.

The threat of rising sea levels and increased numbers of storms and storm surges mean the local governments are likely to implement restrictions on coastal developments and to refuse consent applications for alterations and additions to existing building in low-lying coastal regions.

 

 Updated: 09 May 2016