Designing for your climate

Weather, climate and your home

Sun, wind, rain, temperature and humidity will all influence your enjoyment of a property, so it's important to think about these factors in the design and construction of any new home or renovation.

By taking climate into account, you can:

• get a more comfortable home with lower heating and cooling costs
• increase the resilience of your home and property
• reduce the maintenance needs, through smart specification of materials and fixings.

Sun

Ideally, your home let in plenty of sun in winter or in cooler climates, but not too much in summer or in warmer climates.

Access to sun is affected by the site's shape, slope, built-in external shading and obstructions such as hills, trees and other buildings. Check out all of these factors when you look at how much sun the site will get at different times of day in summer and winter.

House orientation has more information about positioning a home to make the most of the sun.

Rainfall

The amount of rainfall, its intensity and the direction it comes from will influence the design of your home or renovation.

Buildings with eaves over windows and sloping roofs are generally better for areas of high rainfall.

Good drainage is important to reduce issues with ground stability and stormwater runoff during high rainfall events.

Moisture can cause long-term damage.

Wind

Wind direction, strength and seasonal variations will affect the structure and design of your home or renovation. Exposure to wind may influence window and door placement. Weathertightness problems are likely to be worse in high wind areas driving water through cracks and openings.

Wind will also affect your enjoyment of outdoor living.

House orientation has more information on how wind influences design.

Wind zones

If you're planning a new home or extension, your designer or engineer will need to determine the property's 'wind zone' (the forces that will affect the building). Wind creates stress on buildings, which need to be constructed to withstand both horizontal pressure and vertical lift. Bracing and structural details become important.

Your property could be classed as being in a low, medium, high or very high wind zone, or it could be classed as needing a 'specific engineering design' to cope with wind forces. Many councils have this information available on their online property webmaps.

The wind zone will determine how strong any building needs to be, what materials should be used, and how it should be maintained.

The designer or engineer will take into account:

• wind region – New Zealand is divided into two wind regions
• lee zones (low pressure areas)
• topographic class – wind speeds up as it passes over or between hills, or through valleys (this is the 'wind tunnel' effect)
• ground roughness – wind slows down as it goes over rough terrain
• site exposure – other buildings or landforms can provide protection from wind (your property will be classed as 'exposed', 'sheltered' or somewhere in between).

Designing for wind on the BRANZ Level website has more information about analysing a site.

Snow

If your property is in an area with the potential for heavy snowfall, your roof and other parts of your home's structure will need to be strong enough to cope with this load. Snow loading can affect the design of lintels, rafters, ridge beams and veranda beams on your house.

Your engineer or designer will work out the snow loading.

Corrosion

All homes in New Zealand are classified into corrosion zones, reflecting their exposure to sea spray and geothermal areas.

This zoning affects the materials you will use to build your home or renovation – especially claddings, metal fastenings and flashings. For example, steel fastenings will corrode or rust more quickly than stainless steel fastenings when exposed to sea spray.

The corrosion zone will affect the guarantees manufacturers offer on their products and what maintenance you must carry out to ensure that any warranties remain valid.

Microclimate

An individual site's temperature, humidity, wind and rain may vary from the prevailing regional climate. The microclimate can affect the energy performance of a building and types of vegetation that can be grown.

For example, check for areas that are sheltered from prevailing winds, are obviously dry or wet and where heat seems to collect either from exposure to sun or from nearby heat sinks such as walls and areas of concrete.

An area's microclimate is also affected by topography, adjacent buildings, vegetation, bodies of water (including small creeks) and slope. These can all have an impact on air movement, temperatures and access to sun.

Design your house to respond to this microclimate. For example, your location may be in a climate zone where the Building Code requires relatively little insulation, however, your building site might be very exposed to cold southerlies and experience a lot of shading. It may therefore be worthwhile to use substantially more insulation and better glazing than required by the Building Code.

Climate change

Before you buy or build on a property, it's worth considering how the site will cope with:

• severe wind and rain storms and associated flooding
• hotter summers with more frequent droughts and fires, predicted especially for the east of New Zealand
• wetter winters
• a rise in sea, lake or river levels and increases in storm surges and coastal erosion.

There are many measures you can take to address climate change including:

• increasing the steepness of the roof pitch and designing for a higher wind zone
• design with flooding in mind for the lowest levels of the house and install essential, vulnerable equipment as high as possible
• openable, securable windows, capable of allowing a high volume flow of air for summer cooling
• good solar control for windows, ideally including external movable shading for eastern and western aspects, and appropriately sized overhangs for northern aspects
• adequate ventilation on calm days.

As a side effect of climate change it is likely that your insurance premiums for climate-related natural disasters will increase. If you design your home to be more resilient you may be able to save on insurance premiums in the future.