Insulation is the single most important thing for minimising energy consumption in your home. Here's everything you need to know.

Photo by Erik Mclean / Unsplash

Home insulation is crucial in maintaining a comfortable and energy-efficient home.

Insulation not only improves the comfort level of a home but also reduces energy costs and greenhouse gas emissions. This article provides information and advice about home insulation in Australia, including geographic requirements, ratings for insulation products, installation, maintenance, and effectiveness.

All insulation materials that are sold in Australia must meet Australian Standard AS/NZS 4859, Materials for the thermal insulation of buildings.

Insulation Ratings

Insulation ratings measure how effective the insulation is in resisting heat transfer. In Australia, the insulation rating system used is the R-value.

The R-value is a measure of how well an insulation material resists the transfer of heat through it. The higher the R-value, the more effective the insulation is in preventing heat transfer.

The R-value requirement for insulation varies based on the climate zone. For example, the minimum R-value requirement for ceiling insulation in a tropical zone is R2.5, while it is R4.1 for a cold climate zone.

Calculating R-Value

The R-value is calculated based on the thickness and thermal conductivity of the insulation material.

To calculate the R-value you divide the thickness of the insulation in millimeters by its thermal conductivity in watts per meter per degree Celsius. The resulting value is the R-value.

For example, if you have insulation that is 200mm thick with a thermal conductivity of 0.035 W/m°C, the R-value is 5.7.

Geographic Requirements

Australia has a diverse range of climates, from tropical to temperate to arid, and different insulation requirements based on the specific location.

The Australian government has divided the country into eight climate zones, and the insulation requirements differ for each zone. For example, homes in the tropical north require insulation that helps to keep them cool and comfortable during the hot and humid summer months. In contrast, homes in the southern states require insulation that provides warmth during cold winters.

The minimum R-value requirement for ceiling insulation in a tropical zone is R2.5, while it is R4.1 for a cold climate zone.

Zone Description
zone-1 Climate zone 1 Hot humid summer, warm winter
zone-2 Climate Zone 2 Warm humid summer, mild winter
zone-3 Climate zone 3 Hot dry summer, warm winter
zone-4 Climate zone 4 Hot dry summer, cool winter
zone-5 Climate zone 5 Warm temperate
zone-6 Climate zone 6 Mild temperate
zone-7 Climate zone 7 Cool temperate
Alpine Climate zone 8 Alpine

Types of Insulation and R-Value

Insulation products come in 2 main categories — bulk and reflective — which are sometimes combined into a composite material.

Bulk insulation

There are several types of bulk insulation available in Australia, and each has a different R-value per unit of thickness. Here are some common types of insulation and their R-values per 100mm:

Material R-value range per 100mm
Fiberglass batts R-1.6 to R-2.2
Cellulose insulation R-1.8 to R-2.2
Spray foam insulation R-1.9 to R-3.5
Polystyrene insulation R-2.2 to R-2.6
Polyurethane insulation R-3.3 to R-3.8

The R-value for any product type will vary depending on the manufacturer and specific product.

Additionally, the thickness of the insulation will also affect the overall R-value. Thicker insulation will have a higher R-value than thinner insulation of the same type.

Reflective insulation

Reflective insulation resists radiant heat flow because of its high reflectivity and low emissivity (ability to re-radiate heat). This kind of insulation relies on the presence of an air layer of at least 25mm next to the shiny surface.

The thermal resistance of reflective insulation depends on the direction of heat flow - it's designed to resist transmission of radiant heat that will be reflected away from the shiny size, but heat originating from the non-shiny size will not be resisted as effectively.

Reflective insulation is usually shiny aluminium foil laminated onto paper or plastic and is available as sheets (sarking), concertina-type batts and multi-cell batts. These products are known as reflective foil laminates (RFL).

Because any foil insulation is electrically conductive, the risk of contact with electrical cables and equipment must be considered with all installations, and measures to eliminate this risk should be followed.

Composite insulation

As the name suggests, composite insulation combines bulk and reflective insulation into a single product, such as foil-faced boards, reflective foil-faced blankets and foil-backed batts.

The orientation of the foil needs careful consideration to ensure it is most effective and does not add to condensation risk.

Reflective foil insulation should be installed facing the warm side of any building system. Generally, in cooler climates, this means placing the foil on the inner side of the bulk insulation (foil facing inwards), with an air gap of at least 25mm between the foil and the ceiling material.

In hot humid climates and in air-conditioned buildings, it's usually better to have the foil facing outwards, since the main source of heat will be from the outside.


Proper installation of insulation is essential to ensure it performs well. Insulation should always be installed by a professional installer who can provide advice on the best insulation material, thickness, and R-value for your home.

The installer will be able to ensure that there are no gaps or spaces between the insulation and the structure of the home. Any gaps can result in heat loss or gain, reducing the effectiveness of the insulation. It is also essential to ensure that the insulation is installed in a way that allows for adequate ventilation to prevent condensation.


Insulation does not require much maintenance, but it will generally lose some effectiveness over time.

You should check your insulation periodically for damage, dampness, or pests. If insulation gets wet, it can lose its insulating properties, and damp insulation can also encourage the growth of mould and mildew. Insect and rodent infestations can also damage insulation, and any damage should be repaired or replaced immediately.


Home insulation is an essential aspect of maintaining a comfortable and energy-efficient home in Australia. The insulation requirements vary based on the specific climate zone, and the R-value rating system is used to measure the effectiveness of insulation.

Homeowners should seek advice from a professional installer to determine the best insulation material, thickness, and R-value for their home.

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