Cost indication

Low to Med

Effectiveness rating



As we saw in the previous section, insulation works in tandem with thermal mass to maximise the benefits of storing heat. Without adequate insulation, other sustainable features in a home will be rendered ineffective as heat will travel in and out of the home freely. The idea of insulation is to act as a barrier to heat, preventing heat from flowing out of the home in cooler weather and reducing the amount of heat entering the home in hot weather.

Insulation is needed in the ceiling, walls and floor. In terms of product, there are a variety of different types of insulation available in New Zealand. Glasswool insulation is made from recycled glass and is the most commonly used insulation for walls and ceilings because it does not burn easily and is cost-effective. Other options include wool and polyester insulation but these all need to be separated from heat sources due to their greater combustibility.

In terms of the durability aspect of sustainability, insulation products represent good value for money as they have a lifespan of 50 years or more.

Polystyrene boards with a damp-proof membrane are generally used as insulation under concrete slabs. However research has shown that slab perimeter insulation is more essential than insulation underneath the slab as most of the heat loss from the slab occurs at the edges between the air and the ground.

According to studies carried out by BRANZ, combining under-slab insulation with insulation around the slab edge can result in improvements of thermal performance of 100% or more. Perimeter insulation is therefore really worth doing as it results in significant gains in energy efficiency.

You can also improve your home’s energy efficiency and thus sustainability by using thicker insulation in your walls and ceiling to bring the R-value above the minimum required. In our experience, additional money spent on extra insulation is money well spent as you will get it back in reduced heating and cooling costs over the lifetime of your home.