Future-proofing your home

There’s more to building a ‘‘sustainable’’ home than adding a heat pump or solar water heating.

If you are serious about building an energy-efficient home, you have to look at numerous aspects – and call in the experts.

A truly ‘‘passive’’ house is designed to keep occupants at a comfortable temperature using the home’s physical structure and site conditions alone, requiring little or no extra energy for heating, cooling and ventilation.

Although specific design approaches may differ, the core elements are the same: good solar management, good insulation, well-controlled ventilation and careful use of high-mass material.

Such a home will improve your quality of life and save money in the long run, even if it is a little more expensive to achieve.

It is also easier and cheaper to get it right from the start, than to make changes once it is built.

The key is to choose a designer and tradesmen familiar with sustainability principles – after doing your homework and getting several quotes.

Consider using resources like Homestar – which accredits buildings with energy ratings – to ensure insulation. you are working towards a ● Built on an insulated concrete certain efficiency standard. slab.

General design features: ● Energy-efficient lighting.

● House sited to harness the ● Solar, wetback or heat-pump sun’s free heat and avoid shade. water heating.

● Shape simple to reduce thermal ● Most glazing to the north; weak points (corners). minimal to the east, west and

● Above-code, snug-fitting south.

● All glazing, including skylights, ● Overhangs and other exterior double, low-E and argon-filled, shadings exclude summer sun. with thermally broken ● Living areas sited to the north aluminium frames. or west; bedrooms and kitchens

● Doors and windows tightly east; garages, laundries and sealed to exclude draughts. toilets south.

● Roof designed to allow for solar ● Cross-flow ventilation across hot water and photovoltaic the width of the building. panels. However, getting it right is not simple. For instance, achieving the right amount of ‘‘solar access’’ to warm the house in winter, but not overheat it in summer, means balancing location, orientation, room layout, window design and shading.

Ditto light; large windows that admit high levels of light can overheat the room, especially if they cast light on a thermal mass.

If your preferred site does not have good solar access – for example, where the north face is narrow – compensate with building features and design strategies:

● Draught-proofed house to minimise heat loss.

● Total window less than 20% of the floor area.

● Insulating drapes to improve window efficiency.

● Higher window sill heights and high clerestory windows.

● Lower thermal mass.

For detailed information on building a sustainable or truly passive home, see the experts.

Useful references:

● branz.org.nz (factsheets on the best-performing home energy technologies for New Zealand); homestar.org.nz; level.org.nz; ecobob.co.nz; sketchUp.com; nrel.gov/buildings/sunrel; graphisoft.com; snughome.co.nz; settlement.co.nz; righthouse.co.nz; niwa.co.nz/solarview; yourhome.gov.au; renew.org.au; sustainability.vic.gov.au