It doesn’t necessarily cost more to build an energy efficient home, and you'll get better comfort and lower energy bills for years to come.
- Architects, designers and builders
- Site position
- House size
- House shape
- Retaining heat
- Thermal mass
- Case study - The Little Greenie
It’s important to work with architects, designers and builders who understand energy efficient design principles. They know how to make best use of the sun when designing your house. Not all architects, designers and builders are experienced with this, so it pays to shop around and get references.
The best building site for a warm, energy efficient home is north-facing, sunny and sheltered from prevailing winds. On clear winter days the sun sends around 500 Watts of heat through each square metre of unshaded north-facing window. A home designed to harness the sun's free warmth:
- is placed on the sunniest part of the section – to access the most sun
- is oriented to face the sun - with the main living areas to the north and service areas (for example garages and toilets) on the south side
- has good insulation - to trap in the free heat from the sun
- uses thermal mass - like a concrete floor, exposed to the sun so it soaks up heat during the day and releases it when temperatures drop at night
- has appropriately sized and positioned windows – moderately large on the north-facing side of the house, smaller on the east and west sides, and smallest on the south side.
Design a house that is efficient for your household’s needs. Smaller houses are cheaper to build, easier to heat and use a lot less energy.
The more complex a home's shape is, the more floor, wall and ceiling area it has to lose heat through. Simple house designs - for example compact square shapes and multi-level homes - have less external surface area, so are easier and cheaper to keep warm. Houses with north-facing windows can maximise the free heat they get from the sun. These windows should be energy efficient to retain as much of this free heat as possible.
Good design, materials and construction will enable your home to retain heat. The important factors are:
- insulation in ceiling, walls and underfloor
- double glazing with insulated frames
- air locks at external entrances to keep out cold draughts
- building airtightness and controllable, heat recovery ventilation.
Thermal mass is a term used to describe solid materials that absorb heat in daylight and release it when temperatures drop at night. If you build a house with windows that face north and rooms that get direct sunlight, adding or exposing existing thermal mass will make better use of free heat from the sun.
- If you have concrete under your floors - consider exposing it (you can polish or paint it) where it gets direct sun.
- If you have wooden floors - thermal mass can be added by pouring 50mm or more of concrete on top of the wood. Check with a builder to see if your floors are suitable for this option.
Ventilation helps remove moisture and maintain air quality. In summer, it’s the key to keeping your house cool and comfortable. The key things to know about ventilation are:
- most houses can meet Building Code requirements with adequately sized and located windows that can be opened
- room layout and window placement can be designed to enable effective cross-ventilation
- well-designed and installed home ventilation systems can provide good ventilation but performance varies widely
- most homes shouldn't need ventilation systems to stay well ventilated - simply opening doors and windows regularly does the job.
Good design will cut your home's heating needs, but it still pays to make the heating system as energy efficient as possible. There are lots heat pumps, pellet fires, log burners and flued gas heaters on the market, either as central heating systems or as individual heaters to heat areas of your house as required. Not all are created equal - for example, some heat pumps are twice as efficient as others - so it pays to do your homework.
If you design your house really well, you may be surprised by how little heating it needs. One option is to live in your new house for a while before installing heating so you can work out how much heating you actually need.
The 'Little Greenie' house in Golden Bay is a great example of energy efficient building techniques. It’s designed with 5 major principles in mind: energy efficiency, low maintenance and longevity, ease of construction and value for money.
- Good orientation and compact house design – oriented to get the best from the sun and to reduce heating loads.
- High levels of insulation, thermal mass and airtight joinery - retain heat from the sun. This ensures a constant temperature of between 18 and 24oC without additional heating.
- High efficiency double glazed windows and doors - provide controlled ventilation.