Designing a new home

A well-designed house can give you all the warmth, comfort and convenience you want, yet use a surprisingly small amount of energy. It needn't cost much more to build a home designed with energy efficiency in mind and you'll enjoy the benefits for years to come.

Below are the key elements of energy efficient house design.

Size your house to suit your needs

Design for the sun

Keep in the heat - insulation, double-glazing and airtightness

Heating and ventilation strategies

Get your plans energy rated

Saving money up front when designing and building your house can be false economy. It can lead to higher energy bills for years or decades after that.

Size your house to suit your needs

Think about how much space you use on a day-to-day basis. Designing a house big enough to cope with all your relatives once a year is generous but impractical. Smaller houses are cheaper to build, easier to heat and use a lot less energy.

Design for the sun

Position your house to make the most of the sun

With the right balance of north-facing glazing, insulation and thermal mass your home can soak up free heat from the sun and keep you warm day and night. On clear winter days the sun provides unshaded north-facing windows with about 500 Watts of heat per square metre, so it's worth making the most of that free energy.

Place living areas and rooms you use a lot on the north-facing side of the house so they make the most of the heat and light from the sun. Locate less used rooms like the bathroom, laundry and garage on the south-facing side. This will act as buffer against heat loss. 

Use thermal mass

A concrete floor exposed to the sun will soak up heat during the day and release it at night. The concrete slab needs to be well insulated both underneath and around its perimeter. To work effectively, it must not be covered with insulating floor coverings such as carpet in areas that are exposed to the sun.A concrete floor exposed to the sun will soak up heat during the day and release it at night. The concrete slab needs to be well insulated both underneath and around its perimeter. It shouldn't be covered with insulating floor coverings such as carpet. 

Think about direction when choosing window sizes

A lot of heat can be lost through windows if not sized properly for the direction they're facing - even if the windows have double-glazing.

Ideally, windows should be fairly large on the north-facing side of the house (provided they are unshaded), moderately sized on the east and west sides, and small on the south side.
You can find more detailed information and advice in the manual Design for the Sun.

Insulation, double-glazing and airtightness

Install plenty of insulation

Good insulation is the key to a warm and comfortable house that doesn't cost a fortune to heat. And the best time to do it is when you are building so you can access all areas as you go.

All new houses are required to be insulated to a minimum level under the Building Code. To improve your home's comfort, it is worth exceeding these minimum requirements - especially if you are in a colder part of the country.

If your garage is connected to your house, make sure it's insulated too. The best way is to insulate the internal walls and ceiling between the garage and the rest of the house.

How well the insulation is installed is just as critical as the level of insulation. Make sure your insulation is installed according to the New Zealand Standard 4246:2006.

Find out more about insulation in the Department of Building and Housing's Your Guide to Smarter Insulation.

Use good double-glazing with insulated frames

Double glazing is now standard in new homes as it is the easiest way to meet the current Building Code insulation requirements. It lets in heat and light like other windows, but holds in the heat much better.

Some double-glazing is better than others. For best performance, look for the following things.

  • Frames that are thermally broken, or made from an insulating material such as PVC or wood. These will perform better thermally than windows with standard aluminium frames. It can reduce window heat loss by about 20% (thermally broken aluminium frames) to 40% (PVC or wooden frames), compared to double-glazing in standard aluminium frames.
  • Low-emissivity (low-e) glass. This allows light and heat in, but reflects escaping heat back to the inside. Low-e glass cuts window heat loss by about 20% to 30%, compared to double-glazing without low-e.

  • An inert gas filling (such as argon) between the glass layers. This acts as a better insulator than air, reducing window heat loss by about 3% to 9% compared to double-glazing with air filling.

Make your house as airtight as possible

Even well-insulated houses can be hard to heat if draughts constantly replace hot air with cold air. Good building airtightness, coupled with controllable ventilation provisions (like openable windows, vents or mechanical ventilation systems), lets you manage air replacement and avoid unnecessary heat loss.

For good airtightness, the joinery and the wall, floor and ceiling construction should be well sealed. This can be done with special membrane systems - basically high-tech versions of building paper - which are installed in the floors, walls and ceiling of houses while they are being built.

It is important to plan for airtightness during the design stage to ensure all design details allow for proper, continuous sealing without gaps.

Heating and ventilation strategies

Consider how the house will be ventilated

Proper ventilation helps create a healthy indoor environment by maintaining good air quality and removing moisture. In summer, ventilation is key to keeping your house cool.

The Building Code has minimum ventilation requirements. Most new houses can meet these with adequately sized and located windows that can be opened. Opening doors and windows regularly is the simplest and cheapest way to ventilate your home.

Well-designed and installed home ventilation systems can also provide good ventilation, but performance can vary widely depending on the type of system, how well it is installed, the type of house and the climate. Some ventilation systems can reduce heat loss by using a heat exchanger to retain warmth from indoor air as it passes outside.

Find out more about ventilation and ventilation systems.

Consider your heating options

Once your house is designed to be heated cheaply and efficiently, it makes sense to look at good heating options. There are now lots of efficient heat pumps, pellet fires and log burners on the market, either as central heating systems or as individual heaters to heat areas of your house as required.

Find out more about options for home heating and cooling.

Get your plans energy rated

You can get a home rated while it is still in the planning and design phase through the Home Energy Rating Scheme (HERS). Getting a HERS assessment done on your house before it is built allows you to modify the design to maximise the energy efficiency and comfort of your new home and lets you weigh up the impact of different design choices.

More information

From the Resource Centre

Related documents and additional information: