Insulation

Good quality, well-installed insulation will significantly reduce energy losses in all parts of your house: ceiling, underfloor and external walls. It will also mean lower power bills and a healthier home.

Insulation works by reducing the rate at which heat passes through ceilings and walls. Insulation such as fibreglass, cellulose, polyester or wool fibre traps air in small pockets and provides a barrier to warm air escaping. Reflective foil is commonly used under floors.

If a house already has a thin and ineffective form of insulation (less than 120mm), it's worth adding a thick extra layer on top.

Insulation for old and new homes

The New Zealand Building Code specifies minimum mandatory insulation standards for new houses, but many of us are stuck with inadequately insulated older homes.

It’s difficult to insulate the walls in houses that are already built, whereas it’s easier to insulate the ceiling and under the floors, where 33% of heat loss occurs.

Underfloor insulation

Insulating the ceiling and under the floors does not require major renovation and can be done at a reasonable cost. Putting insulation in the ceiling alone can cut heat losses by as much as 35%.

Underfloor insulation can reduce energy losses by up to 14%. In houses with damp basements, a well-installed layer of underfloor insulation will also prevent moisture from penetrating into the house through gaps between floorboards. This results in a significantly higher room temperature and dryer air.

The New Zealand Building Code requires a minimum of R1.3 for floors throughout the country.

Choosing insulation

There is a variety of insulation on the market, however, product quality varies and it’s important to choose the right type for your project.

Well-made insulation is more likely to do its job and remain effective for years to come. EECA recommends products tested to the AS/NZS 4859.1 standard, ‘Materials for the thermal insulation of buildings. Part 1: General criteria and technical provisions’.

These products have been through a series of tests for thermal performance. By choosing insulation products tested to the standard you know you’re getting exactly what you’re paying for.

Compliance with the standard is likely to become mandatory for all insulation products used in new houses.

Installation quality

Good quality insulation is essential for maximum heat retention. Poorly installed insulation is likely to loose up to 50% of its designed R-value. Heat  funnels through gaps just like water escaping from a barrel with a tiny whole in the bottom. 

EECA has developed a set of guidelines for installing insulation products.
Download the Best practice guide to insulation installation [PDF 610 KB]

In 2007, Standards New Zealand is set to publish a new standard on installing insulation. It will cover a variety of products available and will provide detailed instructions on how they should be installed.

Winter insulation

Unprotected, single panes of glass lose 10 times more heat than the same area of insulated wall. Good curtains or blinds can almost halve overnight winter heat loss through windows.

Double-glazing is a way of creating an insulating layer of air between two panes of glass. A well designed double-glazed window with wooden frame can halve energy loss through the window. Double-glazing has been found to be a cost effective way to save energy, even in the warmer parts of New Zealand.

Window and external door frames can also influence the energy efficiency of your home. Heat loss through metal window frames without thermal breaks can be higher than those through timber or vinyl frames.

Design tips

• Use close fitting, heavy curtains or blinds that seal at the top and along the sides of the window frame.
• Use double-glazing where other window coverings are impractical, such as skylights, or where you want to have a clear view of a feature outside.
• If you need to prioritise, install double-glazing to the main heated areas and large windows, and use good curtains elsewhere.
• Look for double-glazed units with a 6mm to 20mm sealed air gap between the panes.
• Close your curtains and blinds when the heater or fire is going.