Whether you are building or renovating, take the opportunity to choose the right insulation for your home – it will help you maintain the best ambient temperatures for health and comfort.

How insulation works

Insulating your house when building is the most effective way of ensuring your house stays warm and saves on heating bills. Cold damp homes can affect your family’s health.

Insulation works by reducing the transfer of heat by means of a barrier. The measure of insulation is expressed as an R-value, which is a product’s resistance to heat flow. The higher the R-value the more effective the insulation is in resisting heat transfer.

The most common R-value in new homes for walls and roofs is between R1.5 and R3.0, depending where you live. You can ask for higher R-values in your insulation for more comfort and savings on heating. The extra cost of installing better insulation may be offset by savings in energy costs.

Research shows that older, uninsulated homes lose 42% of heat through the ceiling and roof, 24% through walls, 12% from ventilation, 12% from windows and 10% through the floor.

Energy efficient houses benefit New Zealand by reducing energy consumption, reducing greenhouse gas emissions and improving people’s health.

Insulation also helps to control noise within the house and from the outside.

Insulation needs complete coverage

Insulation is only effective if it achieves unbroken coverage around the building. If there are any breaks in the insulating material, heat can escape. A common example is steel wall framing which interrupts the insulation and acts as a thermal bridge. Heat loss along thermal bridges can be minimised by using thermal breaks. Material that does not conduct heat, for example polystyrene, is placed between the steel framework and the outside building material. This is something your designer should know about. Compliance with the Building Code requires thermal breaks to be used when steel studs are used in wall construction.

If you are putting in insulation later, for example when you are renovating, be conscious that any gaps or interruptions in the insulating material will seriously reduce its insulating qualities.

Legal requirements for insulation

It is mandatory under the Building Code for houses to meet heating energy requirements. This is usually achieved by following the New Zealand Standard NZS 4218:1996, as referenced in Acceptable Solution H1/AS1, which specifies minimum insulation requirements for housing and small buildings.

SNZ/PAS 4244:2003 ‘Insulation of Lightweight-Framed and Solid Timber Houses’ is a Publicly Available Specification (PAS) that contains guidelines on the selection of insulation levels and window options to improve energy efficiency of houses beyond the requirement of the Building Code.

The PAS specifies thermal insulation values for houses, for three levels of energy efficiency: Building Code compliance, better practice and best practice. It also explains the needs of houses in different climate zones.

If you are interested in working with your designer to get the best possible insulation solutions for your home, it is worth obtaining your own copy of this PAS from Standards New Zealand.

Types of insulation

Generally the thicker the product, the higher the R-value. NZS 4218:1996 suggests minimums for R-values. Insulation is provided by a variety of materials, some of which are better for different areas of the house. Examples are:

• Fibreglass.
• Foam.
• Polyester.
• Polystyrene.
• Wool.
• Flax.

When choosing, consider products which:

• Are non-combustible/fire resistant.
• Are vermin resistant.
• Stay mould-free/will not rot.
• Will provide acoustic insulation.
• Perform over time.
• Come with a BRANZ appraisal.
• Are easy to fit if you are doing it yourself.
• Are non-toxic/non-irritant.
• Won’t sag over time.
• Breathe.

For more information about different types of insulation, go to consumer.org.nz. Note: you need to be a member to access this information.

Further information

The Building Research Association of New Zealand (BRANZ) has produced a bulletin in the Home Series Reducing Heat Loss which has information about ways to increase, adapt or add thermal insulation to new and existing homes, ways to save on your heating bills, and ways for reducing draughts from open fireplaces, doors, windows and glass. You can purchase a copy of this bulletin online or contact BRANZ on 04 237 1170.

See also the BRANZ Annual Loss Factor (ALF) software programme which allows designers and homeowners to estimate and assess insulation and heating requirements. You can access this online.

Community schemes to upgrade insulation in homes

In some areas in New Zealand, schemes have been initiated to insulate homes. Refer to www.eeca.govt.nz/programmes/residential.asp for more information, including examples of current schemes.