Heating & energy

Insulation

Updated: 19 Dec 2008

Introduction

Good insulation can greatly improve your indoor quality of life, and save money. We explain your options.

Insulation will make your home easier and cheaper to heat in winter. Warm indoor temperatures, along with adequate ventilation, make for a drier and healthier place to live.

In this report we discuss insulation options for new and existing homes, explain changes to the building code that affect insulation requirements, and tell you where to get more information.

Note: this report does not contain test results or brand-specific recommendations, but we do compare the price and specifications of 150 types of insulation presently on the market.

Building Code requirements

By law, since 1978 all new homes and major renovations in New Zealand have had to be thermally insulated. 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 requirements

The new minimum insulation requirements, including double glazing, were introduced in stages around the country.

All new homes and major renovations in Zone 3 (see map) have had to comply with the requirements since November 2007. Zone 2 was included in June 2008 and Zone 1 from 30 September 2008.

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

	Roof	Walls	Floor	Vertical glazing	Skylights
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

	Roof	Walls	Floor	Vertical glazing	Skylights
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 The basics).

There are different R requirements for solid construction houses. Details can be found in Clause H1 of the Building Code.

Before you get started

Before spending money on insulation, sort out draughts. 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 a grant or interest subsidy (see below) to fund insulation improvements.

Are you going to install insulation yourself?

Here are some things to consider before you buy and install insulation:

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).
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. See our downlights report for more information.
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.energywise.govt.nz

Need some expert advice?

If you are unsure about how best to insulate your house, consider paying for a home energy rating. For background information see www.energywise.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.

For a list of qualified home energy rating assessors go to the Association of Building Sustainability Assessors website.

Grants and interest subsidies

The Energy Efficiency Conservation Authority (EECA) offers grants and interest subsidies through its Energywise residential programmes. These are available to fund improvements to insulation and other energy efficiency measures for homes. Only ceilings and underfloor insulation projects are eligible.

There are 3 different funding options available:

For households on low incomes, to be eligible for funding:

Your property must have been built before 2000.
You must be eligible for a community services card. The home grants programme targets households on low incomes.
In some areas people with health problems such as asthma and other respiratory illnesses are given priority because of the significant health benefits insulation provides.

For households or landlords earning less than $100,000 a year, to be eligible for funding:

Your property must have been built before 2000.
You must earn, before tax, less than $100,000 a year (one or two earners) or less than $140,000 a year (three or more earners).

If you are a landlord with low income tenants, there is also funding available through the nationwide rental project. To be eligible for funding:

The property must have been built before 2000.
The tenant named on the tenancy agreement must be eligible for a community services card.

Check www.energywise.govt.nz for terms and conditions or call 0800 749 782.

Material characteristics

These summary tables are adapted from Beacon Pathway's report "Thermal Insulation in NZ homes". For more information on insulation materials and the products available, see Materials and Products compared.