We explain your home insulation options.
Our database lets you compare most insulation on the market.
We discuss insulation options for new and existing homes and explain changes to the building code that affect insulation requirements.
POA stands for “price on application”. Some manufacturers don’t supply estimates of price per m² for their products, so you may have to ask in-store. A few of these products can only be installed by specialists, so installation cost is tied up with product cost – these specialists should usually provide free quotes.
Seal around doors and windows, block off unused chimneys and remove downlights that are not rated 'close abutted' (downlights with air gaps around them).
But remember you will still need to air or ventilate the house to prevent damp accumulating and to maintain air quality. Even on the coldest nights you will need some fresh air in the house. There is a fine line between draughts and ventilation.
You may be eligible for help (see below) to fund insulation improvements.
If you are unsure about how best to insulate your house, consider paying for a home energy rating. For background information see www.genless.govt.nz.
You will receive an independent assessment of the energy performance of your home including how well the building's design, construction and orientation enables it to maintain a comfortable indoor temperature, and how efficient the indoor heating and water heating are. You will get recommendations for the most cost-effective ways to improve the house's energy efficiency and reduce your energy costs.
Warm Up New Zealand: Healthy Homes projects provide free ceiling and underfloor insulation for low-income households occupied by people with health needs related to cold, damp housing. Availability is through regional projects.
Home owners or tenants may be eligible if they have a Community Services Card and the house is occupied by someone under 17 years or over 65 years. People can also be referred to the programme by a health provider if they are at risk from illness linked to cold, damp housing - such as a respiratory condition.
Visit www.genless.govt.nz for terms and conditions and more information.
Since November 2007 the standards of insulation required for new homes and major renovations have been markedly increased. The minimum requirements for energy efficiency in house design and construction are spelled out in the Building Code's energy effectiveness clause H1. The standard AS/NZS4859.1 sets the testing and labelling requirements for insulation materials used in the home and whether they comply with the requirements of H1.
The new minimum insulation requirements, including double glazing, were introduced in stages around the country.
The tables below show an example of the new overall R values for wall, roof, floor and glazing required in different parts of the country for non-solid (timber-framed) construction houses.
Full details of insulation requirements can be obtained from the compliance documents of the Building Code.
|Zones 1 & 2 - North Island excluding the Central Plateau[width=50%]||Roof[width=10%]||Walls[width=10%]||Floor[width=10%]||Vertical glazing[width=10%]||Skylights[width=10%]|
|Building Code NZS 4218:2004||R2.9||R1.9||R1.3||R0.26||R0.26|
|Zone 3 - South Island and the North Island Central Plateau[width=50%]||Roof[width=10%]||Walls[width=10%]||Floor[width=10%]||Vertical glazing[width=10%]||Skylights[width=10%]|
|Building Code NZS 4218:2004||R3.3||R2.0||R1.3||R0.26||R0.31|
To achieve the required R2.0 for the walls of a Zone 3 timber house, for example, you need to install an insulation product with an R value between 2.2 and 2.8. This is because the higher R value for the insulation product offsets the lower R value of the timber framing (see Insulation basics).
There are different R requirements for solid construction houses. Details can be found in Clause H1 of the Building Code.
If you're building a new home, we recommend insulating beyond the code's minimum requirements. For a little extra cost you can get a much higher level of comfort and health, and save on energy bills. In particular consider walls, roof, or underfloor areas that will be inaccessible once the house is complete. You won't get another chance.
Plan a new house to make the most of free solar energy. This is called "passive design". The basic principles are as follows:
Concrete floor slabs should be insulated on the sides and underneath on the perimeter at least.
The first step is to check your current insulation: is there any? What state is it in?
Check what the R values are for your climate zone (see Building Code requirements above).
Make sure all leaks (roof and pipes) are repaired so the new insulation doesn't get wet. Damp insulation is less effective.
Have an electrician check you can safely cover electrical wiring that can't be placed outside the insulation.
If you have recessed downlights that are not closed abutted (CA) rated, replace them to eliminate the air gaps. CA rated recessed light fittings are now available that allow insulation to touch them. If you're not replacing the downlights, check to see how big a gap in the insulation is needed around each light fitting to prevent over-heating.
Choose a product that is independently accredited and complies with the standard AS/NZS 4859.1: 2002. Compliance with this standard is mandatory under the Building Code. A compliance statement must be on the label of the insulation.
Wear a dustmask, goggles, gloves, long sleeved shirt and closed footwear when installing fibre insulation products.
The quality of installation is of paramount importance. Even small gaps will undermine the performance of the insulation. A comprehensive easy-to-use guide on installing insulation is available as a free download from www.genless.govt.nz.
The World Health Organisation recommends indoor temperatures of 18-24°C for healthy living. Cold and damp living conditions affect the health of many people and can worsen the symptoms of illnesses such as asthma, bronchitis and other breathing disorders. Damp also encourages the spread of dust mites which can further worsen these disorders.
Damp insulation within the wall framing dramatically reduces the insulation value, making rooms harder to heat. The combination of cold damp rooms and the presence of some fungi will worsen respiratory problems for the very young and very old.
If the space under the flooring is damp, then it is likely fungi will grow on the underside of timber flooring as well as infiltrating the flooring into the house.
Some fungi which grow within wet wall cavities and under floor boards are toxic. In particular the stachybotrys mould (a type of fungi) produces spores which carry chemical toxins known as mycotoxins. These may cause flu like symptoms. They particularly affect the young, the old and those with weakened immune systems.
Stachybotrys can be present within a damp wall cavity or on the underside of the floor boards with no obvious signs or ill effects, but once exposed or disturbed they will produce airborne spores which can be inhaled by those in close proximity
If stachybotrys is found, you will probably need to leave the home while repairs are made. People working on the removal of affected timber have to wear protective gear.