How much does roof insulation cost?

What is roof insulation?

Insulation is a layer of material that is installed in your roof to act as a barrier to heat flowing in or out of your home. It’s designed to help keep your home warm in winter and cool in summer. If not insulated, about 25% to 35% of heat gain or loss is through the ceiling.

Potential benefits of roof insulation, according to the Australian Government’s YourHome website include:

• Creating a more comfortable environment in your home.
• Cutting cooling and heating bills by up to 45%.
• Significantly reducing noise pollution.
• Increasing the value of your home.
• Stopping moisture problems, such as condensation.

How much does roof insulation cost?

The cost of roof insulation can depend on factors such as the type of insulation, the size of your home and your location. The tradie listing website Service.com.au estimates that, on average, adding insulation to your home could cost between $1,400 to upwards of $4,000. This cost can vary depending on the size of the job and materials used.

To help you get an idea of how much insulating your roof might cost based on its size, hipages, a tradie listing platform, estimates that it can range from $50-$70 per square metre for installation.

When it comes to buying materials, insulation can generally be bought either per square metre or per roll. For example, reflective sarking (a foiled layer of flexible insulation) can cost $3 per square metre or $215 for an 80 square metre roll, while glass wool batts (pre-cut insulation made of glass fibres bound into a texture similar to wool) can cost $6-$10 per square metre.

The type of insulation you choose can play a huge part in determining the cost, as each material will differ in price. For example, Melbourne based installer Pricewise Insulation estimates that polyester batts (made from 100% polyester with no breathable fibres) can cost $15 – $20 per square metre, while a 22.5m x 1350mm roll of reflective foil insulation that has an additional Building Code of Australia (BCA) regulated air cell barrier (added assistance in reducing heat) can cost $395.

For bulk purchases, hipages estimates that the average price for bulk fibreglass is $600 to $1,000 per 100 square metres, while any type of polyester product can be more expensive, increasing to an average of $1,100 to $1,500 per 100 square metres.

Factors that affect the price can include:

• The thickness or R-Value of the insulation material.
• The conditions for installers, such as the roof cavity being too hot, cold, cramped and/or dirty.
• Obstacles in the roof blocking accessibility.
• Uneven spacing across ceiling joints. Generally, the more uneven, the more time it will take to install.

Read More: How much do double-glazed windows cost?

Types of roof insulation

The two main types of insulation are:

• Bulk insulation like fibreglass wool, sheep wool, polyester and stone (rock) wool.
• Reflective insulation, with the most popular example being reflective foil insulation.

Wool insulators are typically lightweight and produced in thick rolls or pieces known as batts. These fibrous materials have pockets of air between them, which blocks summer heat from entering through the roof and stops warmth escaping in winter months. It’s important to note that protective equipment is often required when installing fibreglass batts, due to risks of particle inhalation and/or skin irritation. For irritation free alternatives to glasswool, polyester has become an increasingly popular option. It’s often made from up to 85% recycled polyester and comes in a loose form or pellets that are usually blown into a roof or ceiling cavity. This installation method also includes foam-like insulators. This makes for a quick installation with excellent coverage.

The most costly insulation option is stone wool (also called rockwool) made from volcanic rock. It has superior acoustic and thermal insulating properties and is highly fire resistant. It doesn’t absorb moisture and is also resistant to mould, pests and corrosion.

Reflective insulation is the most basic form of insulation. Often produced as a foil, it’s usually installed under the roofing surface, where it reflects heat or cold away from the home interior. Reflective foil is most effective in warmer climates, where heat penetration into a roof cavity is the primary concern.

What is R-value?

When looking at different types of insulation, a common term that pops up is ‘R-value’. R-value is a rating that determines how effective a material is at preventing heat loss or gain. The higher the R-value, the better the thermal performance, which is typically why products with a higher R-value are more expensive. The R-value may also vary depending on the method of installation.

R-values can range from 1.5 to 7.0. Figuring out the best R-value for your needs depends on what suits your home and the climate in your area. For example, if your climate is quite hot, a lower R-value may be suitable. In colder climates a higher R-value (5.0-6.0) may provide more comfort in winter months.

Can you DIY roof insulation?

While roof insulation costs can be high, attempting to DIY the job without taking proper safety precautions is not advised. Entering the roof space can be extremely dangerous especially when dealing with electricity. Electrocution is one of the biggest risks and can be caused by live wires coming into contact with foil-backed insulation.

Besides the safety hazards, there are regulatory requirements and standards when it comes to installing insulation. Bulk insulation, reflective foil insulation and all electrical wiring that is encased in insulation must meet Australian standards and all listed requirements. To find out more information, refer to Standards Australia.

If you have downlights, YourHome also advises that they can potentially cause ceiling fires when in contact with insulation. It recommends taking care when installing insulation; ensuring minimum clearances around downlights are maintained and that insulation isn’t covering any electrical devices such as transformers.

With this in mind, even if you have the right experience and tools and are confident in following the safety and building requirements, roof insulation is probably one of the more complex home improvements. You may want to consider whether DIY is the best approach for your roof insulation or whether it should be professionally installed by a licensed installer. A professional can ensure effectiveness, safety and compliance with the building standards in your state or territory.

In terms of professional labour costs, Service.com.au says installer rates usually start at about $40 per hour and can go as high as $150 per hour. Professional installers can often work fast and efficiently so it may be relatively affordable to get professional installation. Additionally, while installers do not have to be licenced to fit insulation, they do need to follow other requirements and laws.

However if you are determined to install it yourself, Better Homes & Gardens recommends making sure you buy the correct width of material to suit the gap between your ceiling joists and to leave a gap around any light fittings to avoid heat build-up and reduce the risk of fire.

Is roof insulation worth it?

If you’re using an air conditioner or heater and your home isn’t insulated, you might be wasting more money than you realise. Insulation can help keep your house cooler or warmer, depending on your situation, and potentially save you up to 45% on your electricity bills. Though that can sound tempting, it may be best to first consider all of the factors before deciding on whether roof insulation will be your next possible home improvement, such as:

• Installation costs.
• Short-term energy and electricity savings.
• Long-term savings (will it save you more than what you spent?).
• Available government rebates.

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