Plan your insulation
Good quality, well installed insulation will significantly reduce the rate of energy loss in all parts of your house: ceiling, underfloor and external walls. It will also mean your house is easier and cheaper to heat.
On this page:
How insulation works
Insulation works by reducing the rate at which heat passes through ceilings, walls 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 often used under floors but better products are becoming available.
If a house already has a thin and ineffective form of insulation (less than 120mm), it is worth adding a thick extra layer on top.
Insulation for new homes
The New Zealand Building Code specifies minimum mandatory insulation standards for new houses. Check with the Department of Building and Housing for changes to the code at Home owners and consumers. [Department of Building and Housing.]
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Choose the right insulation
There is a variety of insulation on the market, but product quality and performance varies. It is therefore important to choose the right type for your project.
Checklist for insulation
1. Quality
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 are getting exactly what you are paying for.
Compliance with the standard is likely to become mandatory for all insulation products used in new houses.
2. Installation
Well installed insulation is essential for maximum heat retention. Poorly installed insulation can loose up to 50% of its designed R value. Heat funnels through gaps just like water escapes from a barrel that has a tiny whole in the bottom.
3. Windows
Unprotected, single panes of glass loose 10 times more heat than the same area of insulated wall. Good curtains can almost halve overnight winter heat loss through windows.
4. Double glazing
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
- is a cost effective way to save energy, even in the warmer parts of New Zealand
- cuts down external noise
- reduces condensation.
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.
5. Window and external door frames
Window and external door frames can also influence the energy efficiency of your home. Heat loss through metal window frames without thermal breaks will be higher than through timber or vinyl frames.
Use close-fitting heavy curtains that seal at the top and along the sides of the window frame. (See Fig. 1.)
Close your curtains and blinds when the heater or fire is going.
Fig. 1 Close-fitting drapes or blinds trap an insulating layer of still air |
Installing standard
Standards New Zealand [Standards New Zealand website.] has published a standard on installing insulation, NZS4246:2006.
It covers a variety of products available and provides detailed instructions on how they should be installed.
You can download a copy of the Standards from the EECA website (PDF, 2.9MB).
More information:
Insulation
- For comprehensive information on insulation, download the Department of Building and Housing booklet Your guide to smarter insulation, PDF 2.9 MB [Smarter insulation booklet.]
- Insulation options [Smarter Homes website.]
Glazing
- Glazing and glazing options [Smarter Homes website.]