Whether you are building from scratch or renovating an existing house, there are a host of ways to make a home environmentally friendly and sustainable. A “green” house is less of a drain on resources, has less of an impact on the environment and can provide a healthier environment in which to live. While some of the measures are more expensive than traditional processes initially, a lot of changes can be made cheaply or at no cost, and almost all will result in cost-savings in the long run.
Eco-building generally aims to have as few negative effects on the environment as possible, to use materials that contribute to a healthy living environment, to make use of natural resources such as sunlight and to improve the indoor air quality.
Think about materials
The first thing to take into consideration in the building process is the materials to be used. If renovating, aim to reuse as much of the existing material as possible, or recycling other building material. An average three-bedroom home generates about six tonnes of waste during its construction. Not only is the timber that was used in houses built in the early part of last century solid and reliable, reusing materials cuts down costs and the toll on the environment. If you have to use new products, opt for those that have not been treated with harsh chemicals and use non-toxic paint. Look for products that were produced locally where possible. Check what will happen to any off cuts and leftovers – can they be recycled?
Consider what the materials have to be used for and how long you need them to last – the footprint of the house will only get bigger if they wear out and have to be replaced. Keep the house well ventilated and use materials which allow it to breathe, and do not give off any chemicals. You will however, need to install fire shutter doors compliant with health and safety regulations.
One of the biggest costs in running a house is heating. The World Health Organisation has reported that almost a third of New Zealand’s housing stock is colder than the recommended minimum of 16C. The ideal living temperatures are about 18C-22C. A few design changes can make a house much easier to keep warm, offering health benefits and cost savings – an eco-friendly house can cut power bills by up to 80 per cent.
Good design will enable a house to harness the natural heat and light of sunshine. Not only should it be able to catch as much as possible, a well-designed house should retain it easily. Windows should be north-facing and skylights can be put in dark rooms. Wide eaves stop houses getting too hot in summer and maximise winter sunshine.
Install double-glazing on windows and aluminium joinery to retain the heat. Thermal-backed curtains are better than blinds for keeping the house warm and should be drawn when the sun goes off the house. Concrete floors act as a thermal mass to absorb heat during the day, which is then released through the house as the temperature drops. Seal draughts and cracks in the house. Install energy-efficient heating methods such as heat pumps, set on timers. When buying new appliances, opt for those with good energy-efficiency star ratings. A three-star fridge can use twice as much power as a six-star version. Flow restrictors on taps and showerheads will cut the water heating bill and the amount of water used.
Install insulation in the walls, ceiling and under the floors. The Government is offering financial assistance to insulate houses built before 2000 – for new houses, insulation can be installed well beyond the R-value specifications of the building code. Other quick ways to cut the power bills of any house include lowering the thermostat on the hot water cylinder, wrapping it and the pipes, and replacing light bulbs with energy efficient ones.
A house that is oriented north will generally be warmer and easier to keep free of damp. Some rooms will have to be on the southern side, but they should be the bedrooms and bathrooms, rather than the living areas. These will also act as a temperature “buffer’”, to help keep the living areas warm.
How much do you really need?
Don’t build a house that is bigger than you really need. A smaller home is less of a drain on the environment and costs less to heat. Think about how the house will need to adapt for the future – it might cost a bit more to future-proof it during the design stage, but it will be cheaper than moving, or extending the house, when your family grows out of it.
When planning the design, take into account the natural contours of the section and try to work with them. Soil type, climate and landforms will help determine what can be done on the site. Design the garden around any established trees or waterways. Try to minimise the house’s impact on the site – one with a smaller “footprint” will be cheaper to build as well as easier on the environment.
Becoming more self-sufficient can save money as well as reduce the drain on natural resources. A water tank can be installed to provide drinking water, and systems set up to irrigate the garden with grey water. Solar water heating can provide up to 80 per cent of water heating and the EECA offers a grant to help with the installation costs. The design of the house should take into account efficient water use and disposal of waste water. Water retention tanks can be used to moderate the house’s load on the stormwater system.