Passive Design

Climate change affects home design in two ways. Homes will have to be designed to respond appropriately to a climate with higher temperatures, different wind and rainfall patterns, and potentially increased incidence of hazards such as flooding and storms. New Zealand homes have an average lifespan of over 80 years, and some stand for up to 150 years, so homes will have to be able to cope with changes over those timeframes.

Homes also have to be designed to minimise emissions of carbon dioxide and other greenhouse gases over their useable lives. Emissions today will continue to contribute to global warming and rising sea levels for hundreds or perhaps thousands of years.

Designing to cope with climate change

The impact of climate change will vary from region to region. Depending on the region you’re designing for or building in, you will probably need to consider:

• using passive design methods to ensure a home remains comfortable in higher temperatures
• increasing structural strength above current requirements to deal with potential loads from wind
• designing the roof, roof drainage, and stormwater runoff to cope with higher rainfall or more intense rainfall
• ensuring homes are weathertight
• water-saving measures in areas that may be more drought-prone or where warmer, drier weather may put water supplies under pressure
• advising clients against building in flood-prone areas or coastal areas that may be susceptible to severe erosion
• exceeding minimum floor levels and placing vulnerable equipment as high as possible in areas that may be flood-prone.

Designing to reduce emissions

Carbon dioxide and other greenhouse gases are emitted at every stage of a home’s construction and use, including:

• when materials are being extracted, manufactured/processed and/or transported
• during construction
• while people are living in the home – a typical New Zealand home emits more than 3000 kg of carbon dioxide every year
• during and after demolition.

Carbon dioxide is the most common greenhouse gas from homes. An average home produces far more emissions while it’s lived in – for example, through energy use – than during construction.

Limiting emissions from homes makes sense, not only for environmental reasons but also for economic reasons. A home that uses less energy will be cheaper to run and therefore – as awareness of sustainability issues increases – is likely to be more attractive for clients/buyers. And future building regulations are likely to add to energy costs and to costs of materials that are high in greenhouse gas emissions.

Reducing a home’s greenhouse gas emissions involves:

• choosing a site that minimises the need for occupants to use cars for transport
• designing a home that’s an appropriate size – a home that’s too large will waste materials and energy
• using passive design features – such as correct orientation, insulation and so on – to keep a home comfortable, healthy and well lit
• choosing materials that have fewer emissions over their life-cycle, and using those materials efficiently
• specifying energy efficient artificial lighting, heating, water heating and appliances.