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Different types of insulation: the pros and cons

If you want a warm and healthy home, the first thing you need is efficient insulation. New Zealanders have come a long way from the days when the only home insulation was a rug over the knees on cold winter nights.

All insulation works by trapping a layer of warm air within the building’s ceiling, underfloor and wall layers. The theory is straightforward but the practicalities are not. For a start, there are many different types of insulation on the market. Which product is best for you?

They all have their pros and cons. Here’s a quick guide to the main types of home insulation on the New Zealand market.

Fibreglass insulation

This is the type most familiar to Kiwis. We’ve all seen the TV ads. It’s commonly made from recycled glass and offers excellent thermal performance, i.e. it traps heat more effectively than most other materials of the same thickness. On the downside, the glass fibres can be irritating to skin and eyes, while some people have concerns about the chemicals used to bond the fibres during manufacture.

Polyester insulation

This is often made from recycled plastic, such as PET drink bottles – an eco-friendly way to turn a waste product into a green insulation resource. It offers a good level of insulation performance, especially when installed as a large ‘blanket’ that rolls out to cover the entire roof space, including joists. This is an excellent way to minimise hidden heat loss. Harrisons Home Energy Solutions uses a polyester insulation brand that contains no chemical additives, unlike some fibreglass insulation products.

Wool and wool blend insulation

The stuff that keeps sheep warm can also be used to keep your home snug. It’s a natural product, which makes it pleasant to handle. Some brands of wool insulation are blended with resin and polyester to improve their effectiveness. Wool insulation does not work as well as some other types of insulation, so you may need to pay more to install a thicker layer.

Foil insulation

This is basically a special kind of paper coated with bitumen and aluminium foil. It relies on its shiny surface to reflect heat, so corrosion and dust can reduce its effectiveness over time. Foil used in isolation by itself is no longer accepted as complying with the Building Code for underfloor insulation.

Polystyrene insulation

Polystyrene foam is a good insulation material that’s used increasingly in new buildings. It’s a product of the petrochemical industry so is not particularly eco-friendly. However, it needs expert installation to ensure there are no gaps where heat can leak out – these will drastically reduce its effectiveness.