Insulation materials

What insulation works for you?

You can choose from a wide range of insulation materials, each with different properties and features, and each suitable for different parts of the house.

Increasingly, insulation products are available containing recycled material.

Things to consider

R-value

The 'R-value' measures how good the insulation material is at resisting the flow of heat from inside out in winter and from outside in during summer. The higher the R-value, the better the insulation will be. The insulation needs to be properly installed to work effectively.

The Building Code specifies minimum construction R-values for floor, wall, ceilings and glazing. It's a very good idea to exceed the minimum requirements to get a warmer home which is healthier and easier and cheaper to heat.

Insulating for an energy efficient building has more information on insulation levels and requirements.

Insulating your home has more information.

Cost

When comparing prices, you'll need to consider the level of performance you're aiming to achieve, and the type and amount of insulation you'll need across the whole area you're insulating.

You may be eligible for a grant through the government’s Warmer Kiwi Homes programme. The grants can help you pay for ceiling and underfloor insulation, and efficient heating. Check your eligibility.

Insulating your home has more information.

Labelling

All insulation should be labelled with the following information:

• description of bag contents
• R-value with the conditions under which the R-value applies
• safety and handling instructions
• installation instructions
• fire safety.

Blankets and segments should also have information on thickness, length, width and coverage area of the pack. Some products may have acoustic (noise) ratings.

Loose fill insulation should state the thickness of fill required to get the stated R-value.

Long-term environmental impact

When you're comparing insulation materials, the most important issue to consider is:

Provide the highest insulation level you can. Reducing the space heating energy use of a building is usually the single most important thing you can do to reduce the building’s overall environmental impact.

The other issues to think about are:

• how much recycled content the insulation has – recycled content is becoming increasingly common
• whether the material can be recycled at the end of the building's life
• avoid hydrochlorofluorocarbon (HCFC)-foamed insulation materials which may be used in polystyrene products.

The benefits of insulation in reducing home energy use clearly outweigh the energy consumed in its manufacture.

Additional information

Ask suppliers for product data sheets for more information on how the product is made, what it contains and how it performs.

Glass and mineral wools

What is it?

Glass and mineral wool types of insulation are made from fibres made from molten glass (recycled or new) or other minerals.

Mineral wool can contain a large proportion of industry mineral waste. Glass/fibreglass insulation can contain up to 80 per cent recycled glass.

Format

Glass and mineral wool insulation comes in blankets, segments and loose fill. There are a range of R-value products, including quite high R-values for products of standard thickness.

Efficiency/functionality

Glass and mineral wool is a very effective and widely used form of insulation. Products are suitable for ceilings, walls and under-floor, in new builds and renovations.

Toxicity/emissions/air quality issues

Glass and mineral wool products don't emit any harmful airborne pollutants.

You may get some dust from loose fill glass wool insulation, both during installation and afterwards. Mineral wool is generally dust-free.

Fibres can irritate eyes and skin of installers and others in the proximity. When you're installing glass wool insulation, you should use protective clothing and a mask or respirator to prevent inhalation of small fibres and minor skin irritation.

Recyclability/reusability/waste minimisation

If kept dry, glass-based insulation can be recycled. The recycled content contributes to overall minimisation of glass and mineral waste.

Sourcing

Glass and mineral wool insulation are both made in New Zealand and imported. There are a number of suppliers, offering a range of formats.

Sustainability

The base materials used to make glass and mineral wool insulation are non-renewable but very plentiful. Increasing the recycled content of glass wool significantly improves the sustainability.

Polyester

What is it?

Polyester is a synthetic material based on petrochemicals.

Some polyester products may contain recycled polyester fibre. Some New Zealand manufacturers use material from recycled plastic bottles.

Polyester/wool blends are available using up to 40 per cent polyester or recycled plastic fibre mixed with recycled or virgin wool.

Format

Polyester insulation comes in blankets, segments, and loose fill. A range of R-value products are available.

Efficiency/functionality

Polyester is a cost-effective and widely used form of insulation, suitable for ceilings, walls and under-floor in both new builds and renovations. Polyester has similar R-values to fibreglass for same thickness of material.

Toxicity/emissions/air quality issues

Polyester insulation will not emit any airborne pollutants if no chemical binders are used.

It is toxic if burnt.

Dust masks are recommended during installation.

Recyclability/reusability/waste minimisation

Some polyester/wool blends can contain a high proportion of both recycled wool and polyester off-cuts, contributing to general waste minimisation.

Polyester insulation does not degrade and is claimed to be suitable to recycle and reuse.

Sourcing

There are several companies in New Zealand manufacturing and distributing polyester insulation.

Sustainability

It is a by-product of the petrochemical industry. It's more sustainable to use insulation containing recycled polyester than to use insulation made from new polyester.

Wool insulation

What is it?

Wool insulation is made from natural sheep wool (either new or recycled from carpet manufacture offcuts), and may be blended with preservatives, and polyester or resin. Blending is needed to give added strength so the insulation keeps its shape and doesn't slump in wall cavities over time.

It is also treated to make it pest, mould, fire and slump resistant.

Format

Wool insulation comes in blankets, loose fill, and segments. A range of R-value products are available.

Efficiency/functionality

Wool insulation is effective in walls, ceilings and under floors. It generally, but not always has a slightly lower R-value than fibreglass for same thickness of material.

Toxicity/emissions/air quality issues

Wool itself is not toxic. However, it pays to research what it has been blended with. Some resins or binding products could potentially have low levels of emissions when first installed – check with the supplier.

Wool insulation is non-irritating and easy to handle.

Recyclability/reusability/waste minimisation

Wool insulation may be recyclable, depending on what it has been blended with.

Some wool insulation products have up to 100 per cent recycled wool content.

Sourcing

Wool insulation is New Zealand-made. There are a number of suppliers, making different products and formats.

Sustainability

Wool is a sustainable agricultural product.

Polystyrene

What is it?

Polystyrene is a highly processed, synthetic material based on petrochemicals. Fire retardant is added during manufacture.

It is used as stable, rigid foam that can be formed or cut into a range of shapes and thicknesses.

Polystyrene foam is available as extruded, or expanded (commonly seen white format). Extruded polystyrene (usually yellow) is used for specialist construction systems – it is imported and more expensive than expanded polystyrene.

Format

Polystyrene insulation comes in rigid sheets and planks which can be used under concrete floor slabs, under suspended timber floors, in exterior walls as cladding and insulation, and in ceilings. A range of R-value products is available.

You can also get polystyrene 'pods' for use in concrete flooring, and polystyrene insulation can be used in 'sandwich' format in precast concrete panels.

Concrete construction has more information.

Efficiency/functionality

Polystyrene has slightly higher R-values than fibreglass for same thickness of material. It can be used for ceilings, walls and under-floor, although in retrofit situations, it is mainly used under-floor for suspended timber floors. However, it is a rigid material. That means that special care needs to be taken to install it without gaps or to get a snug fit so its overall performance does not suffer.

Toxicity/emissions/air quality issues

Polystyrene is toxic if burnt.

Current products are chlorofluorocarbon (CFC) free but some early extruded polystyrene products used CFCs so care with their disposal is needed.

It's safe if fully sealed by concrete or cladding, so any emissions are contained.

Polystyrene is easy to handle but shreds and crumbs from cutting should not be inhaled. They should be contained and prevented from entering soil and water as they break down very slowly.

Recyclability/reusability/waste minimisation

Expanded polystyrene can be recycled for insulation if it has not been broken up. Recycled polystyrene is available through specialised suppliers or through regional waste recovery centres.

Where possible, use recycled polystyrene sheets for slab insulation.

Sourcing

Polystyrene is either imported, or polystyrene base material is imported and further processed in New Zealand. It can be sourced throughout New Zealand from recyclers, installers and manufacturers.

Some extruded polystyrene sheeting may be imported.

Sustainability

Polystyrene is manufactured from a by-product of the petrochemical industry. It’s more sustainable to use insulation made from recycled polystyrene than to use insulation made from new polystyrene.

Other insulation materials

Paper-based cellulose insulation was used for existing houses where installing blanket insulation would be too difficult, especially in ceilings. Initial R-values were similar to fibreglass, but it settled over time, and older installations (eg from 70s and 80s) are likely to be less effective now and should be topped up. Note that the Residential Tenancy Act makes it mandatory from 2019 that insulation that has degraded over time be upgraded to meet new targets.

Insulation requirements under RTA on the Tenancy Services website has more information.

Pumice is a naturally occurring material that has been used for floor insulation under concrete slabs.

Pipework insulation is used to clad pipes to prevent heat loss and freezing. To achieve best insulation a pipe insulation product made of foam or fibreglass or a similar material should be applied.

Ban on foil insulation (also called reflective)

A ban is in place on the installation, repair or both of foil insulation in residential buildings with existing electrical installations due to safety concerns associated with the installation of the foil in proximity of electrical wiring. We suggest all foil is replaced with an alternative insulation product, as soon as possible.

Foil insulation ban has more information.