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The Ultimate Guide to Roof Insulation

roof insulation guide

If your house was built during the big hair, spandex era of the 1980s, chances are your roof insulation is not up to scratch. Disco was well and truly dead by the time insulation became a standard building material, so it’s possible that your home has never reached peak efficiency regarding heating and cooling.

As a large portion of heat enters and exits a house via the ceiling (between 25 – 35 per cent), insulation is essential for forming a barrier between you and outside temperatures. Insulation is currently a requirement for new builds, with minimum standards set for the various climate zones by the Building Code of Australia.

A well insulated roof and ceiling can block heat from entering in the summer and trap it during the winter – both of which go a long way towards keeping your home comfortable all year round.

The Australian Government’s guide to sustainable living YourHome states that the benefits of a well insulated home include:

● Reducing energy bills by up to 50 per cent
● Eliminating moisture build up and mould
● Lowering your carbon footprint
● Minimising exterior noise
● Adding to the value of your home

The ability to save on energy bills is a no brainer, not to mention boosting comfort and lowering your home’s environmental impact. But what exactly is roof insulation, and how does it work? More importantly, can you save a quid by installing it yourself? Let’s take a closer look:

What is Roof Insulation?

Roof insulation and ceiling insulation are blanket terms covering a wide range of materials serving a unified purpose: increasing the home’s thermal efficiency, which increases the effectiveness of things like air conditioning and gas heating.

Insulation materials including battens, loose fill foam and reflective foil shielding are typically installed by a qualified technician and used in conjunction with one another to manage heat flow and achieve the desirable efficiency.

Modern insulation is non-combustible, meaning the insulation won’t ignite if exposed to fire. However, insulation can cause fires when inappropriately installed around downlights, and reflective foil insulation can carry a current from damaged electrical wiring.

Insulation can have acoustic benefits that block outside noise, but its primary purpose in residential roofing is improving thermal efficiency.

roof insulation pink batts

Types of Roof Insulation

Reflective Foil

Sarking is the term used to describe the outermost layer of insulation fitted immediately underneath roof tiles or metal roofing. Roof sarking is commonly made from a waterproof reflective foil laminate with an outer layer that protects your home during construction, and an inner reflective layer that protects against moisture build up, mould and radiant heat from the sun.

As condensation can form on the underside of metal roofing, a reflective foil laminate is the first line of defence against moisture.

Bulk Insulation

Batts are the most common form of bulk insulation which simply refers to the bulky kind of materials.

These lightweight insulation batts are flexible, made from a combination of glass wool, recycled and unprocessed materials. They are one of the key forms of thermal insulation in modern homes. The major brands who corner the batts market in Australia include Pink Batts, Earthwool and Bradford.

Loose Fill

Made from cellulose or glass wool, loose fill breaks the batt structure down into a more manageable form that can be pumped into hard to reach places like wall cavities and tight ceilings for improving thermal efficiency. A pump is required for the installation so you should leave this material to a roofer or professional insulator.

There’s a stigma surrounding the term loose fill as it was previously used to describe an obsolete form of insulation that contained asbestos. Rest easy knowing that modern loose fill products do NOT contain asbestos.

The Importance of R-Value

Browse any listing for insulation products, and you will surely come across R-value. The R-value is a rating system used by the building industry to determine the thermal resistance of insulation.

Global manufacturer Knauf Insulation explains that the R-Value rating of a product is based on two factors: the thickness of the insulation and the material’s thermal conductivity.

According to YourHome, R-values for roofing products are structured so that homes in cooler climates will benefit from a higher R-value while warm or humid climates suit lower values. For example, roofing in Thredbo requires a minimum 6.3 rating while Cairns has a minimum of 4.1.

The minimum value differs across climate regions, so be sure to check the Building Code or consult a roofer to determine your required R-value.

reflective foil insulation

How Long Does Roof Insulation Last?

Like most things in life, insulation does not last forever. Heat, dust, dirt and pest infestations can all affect the quality of insulation. AGL energy recommends that ceiling insulation should be replaced or retrofitted every 15 to 20 years.

The energy provider also refers to an insulation report that estimates 1.3 million Australian homes built before 1990 do not have any insulation, while another 2.1 million are in need of an upgrade.

The report published by the Insulation Council of Australia and Zealand proposes a model where if every home was to retrofit insulation by 2020, the nation could save a whopping $600 million in annual heating and cooling costs. Greenhouse gas emissions could also be cut by up to 7.1 million tonnes of CO2 each year.

If that doesn’t convince you to upgrade insulation, the report also suggests that every star increase to your home’s energy rating adds approximately three per cent to the value of your home. It’s unclear how this information could be utilised by an eager seller, but it sure makes insulation sound appealing.

DIY Roof Insulation

Can you DIY roof and ceiling insulation? The short answer is yes. The long answer may shock you – quite literally.

If you were hoping to save some money by installing your own installation, then go right ahead. You can always head down to your local trade supplier and pick up batts in suitable sizing and R-value.

However, the work is potentially dangerous, and you must follow appropriate safety precautions to avoid serious injury.

Remember the Australian Government’s failed Home Insulation Program from the late 2000s? Four people lost their lives fitting ceiling insulation due to not receiving the appropriate training or following correct safety practices.

So it’s good to know the potential hazards beforehand: Reflective foil insulation can carry current from electrical wiring. Batts fitted around downlights can start a fire, and it can get hot up there in the roof space, making overheating a real possibility.

Batts also give off fibres that can be dangerous when breathed in. Then there’s the itchiness. Coming into contact with glass wool batts or similar fibreglass fibres can irritate the skin, causing itchiness and inflammation. The same goes for the eyes.

BUILD argues that a dust mask is necessary, and wearing gloves is recommended. The website goes so far as to suggest that due to the potential hazards and the insulation regulations set by Australian Standards, it’s wise to hire a professional.

installing roof insulation

Is Roof Insulation Worth it?

Absolutely. There’s a good chance that if your home was built in the last decade, the insulation in your ceiling cavity already meets Australian standards and does a reasonable job of improving the thermal efficiency of air conditioners and heaters. It’s the homes built years prior that require higher thermal efficiency.

Beyond the increased comfort, there’s potential to reduce energy bills by up to 45 per cent. Outside noises can be reduced and there’s the significant reduction to your carbon footprint. Seriously, what’s not to like about insulation?

Head on over to the Australian Government website to explore what rebates are available in your area.