Insulation effectiveness

There are three key factors that determine whether you insulation will work as well as possible - the thermal resistance (R-value) and quality of the product used and how well it is installed.

If any one of these is substandard, then your home will be harder and more expensive to heat and less comfortable as a result.

On this page:

Product performance - R-value
Product quality
Installation quality
Climate zones

Product performance - R-value

The effectiveness of insulation is measured by its thermal resistance, or R-value. The higher the R-value on an insulation product, the more it slows down the transfer of heat. For a fixed insulation density, the R-value of insulation gets higher as the product gets thicker.

For example an R3.0 product has greater thickness than a R1.0 product of the same type.

Be careful not to use the thickness of insulation to compare different products, always use the R-values, that way you are comparing like for like.

Note: Reflective foils do not have an R-value. The foil helps increase the R value of your floor by trapping air between the floor joists.

Product quality

Well-made insulation is more likely to do its job and remain effective for years to come. Here's what to look for.

• Performance guarantees. Check what sort of performance guarantees the insulation manufacturers offer on their products. The minimum you should consider is 20 years, but some products come with 50 year performance guarantees.
• Product testing. 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. Look for a AS/NZS 4859.1 compliance statement on the insulation packaging.

Compliance with the standard is now mandatory for all insulation products used in new houses.

Installation quality

For insulation to work well it is essential that it's installed properly.

Ensure that there are no gaps between insulation pieces. Also check that no areas of insulation are folded, tucked in or compressed.

The only exception to this are some types of bulked underfloor insulation which are are designed to be folded along one edge when installed between floor joists. These products are designed so that he folds don't effect the thermal performance.

Consider professional installation or download the NZ Standard on installing insulation in residential buildings NZS 4246. The Standard provides good advice on how to install insulation well

Find out more about installing insulation.

Climate zones - what do they mean?

Sometimes you will see details about how much insulation you need based on which climate zone you are in.

New Zealand is divided into three different climate zones based on temperatures common within those areas.

Climate Zone 1

All areas north of, and including, Franklin District. Thames-Coromandel is also part of Climate Zone 1.

Climate Zone 2

All North Island areas not covered by Climate Zones 1 and 3.

Climate Zone 3

All of South Island and North Island Central Plateau (Taupo and Ruapehu Districts, and north of Rangitikei District).

Note: The above is an abbreviated summary of the climate zones set out in the New Zealand Building Code. For the exact definitions, please refer to the Building Code.