Underfloor Insulation: It Works, and It’s Worth Its Weight in Gold

Does underfloor insulation cause dampness?
Does underfloor insulation work? Is it worth the investment – or should you spend your budget elsewhere? Underfloor insulation is often overlooked during new builds and renovations, but it actually plays a crucial role in preventing heat loss and gain in your home. Without it, you could be losing a significant amount of heat in winter and experiencing uncomfortably hot indoor temperatures in summer. If you want to improve indoor comfort, increase your home’s energy efficiency and save money on your power bill year round, don’t underestimate the power of insulating your floors. In this guide, we explain when underfloor insulation is worth it, how effective it is and how you can make the most of your investment.

Does Underfloor Insulation Work?

Underfloor insulation is made of materials that are highly effective at slowing down the transfer of heat energy. Without insulation in your floors, heat will be able to travel through your flooring material without much resistance. This makes it difficult to keep your home at a comfortable temperature, especially if it’s particularly hot or cold outside. When you install insulation inside your home, it helps slow down the flow of heat, keeping indoor temperatures more comfortable. Insulation also helps your air conditioner and heater operate more efficiently and effectively. To work properly, underfloor insulation needs to be installed correctly. It’s also important to choose the right R-Value based on the climate and local building code regulations. Read more about the science behind insulation: How does insulation work?

Is Underfloor Insulation Effective?

According to Your Home, the Australian government’s guide to sustainable homes, installing premium underfloor insulation in your home can reduce energy usage by 10% to 20%. In other words, the right floor insulation could potentially reduce your energy bills by 10% to 20%. Home insulation is a long term investment which can pay itself back in around 3 to 5 years. Modern insulation products are designed to last the lifetime of a home and many popular brands such as CSR Bradford and Knauf Earthwool come with warranties of 50 years or more.

Does Your Home Need Underfloor Insulation?

Most homes need underfloor insulation, including homes with suspended timber floors, suspended concrete floors and concrete slabs on the ground. For concrete slabs in contact with the ground, the best time to install insulation is during construction. Foilboard Slabmate and Slabmate Pro underslab insulation are popular products for this purpose. Most suspended floors can be insulated during construction or as a retrofit in existing homes. Signs you need underfloor insulation in your home:
  • You experience big fluctuations in temperature throughout the day or struggle to keep your home comfortable even with the air conditioner or heater on.
  • You feel air draughts through the floor.
  • You’ve got floorboards that are noisy to walk on – underfloor insulation will help deaden the sound of foot traffic, giving your floorboards a more solid feel.
  • Your floorboards, tiles or vinyl flooring is damaged – add underfloor insulation while you’re replacing your flooring to save on installation costs.
  • You live in an old home – or your existing insulation is damaged and no longer effective.
Also read: When does underfloor insulation need replacing?

Reasons to Invest in Underfloor Insulation

Underfloor insulation offers many benefits for both new builds and older homes. Reasons to invest in underfloor insulation include:
  • Better temperature regulation in your home – achieve more comfortable indoor temperatures all year round.
  • Prevents air draughts – stop unwanted heat loss and gain due to air draughts.
  • Financial savings – proper floor insulation could reduce your power bill by up to 20%.
  • Improved energy efficiency – your air conditioner and heater won’t have to work as hard and will use less electricity.
  • Reduced environmental impact – underfloor insulation is an important part of passive home design and a great way to reduce your carbon footprint.
  • Acoustic benefits – underfloor insulation can help reduce sound transfer, improve sound quality and maintain privacy in your home.
  • Easy to install – in many houses underfloor insulation can be installed as a DIY project.
  • Lifelong investment – modern underfloor insulation products are designed to last the lifetime of your home, which means you can keep saving long into the future.

Does Underfloor Insulation Work in Summer AND Winter?

Yes, absolutely. Thermal insulation works both ways. When the weather is hot, insulation will prevent the heat outside from creeping into your home. When the weather is cold, insulation will prevent the warmth inside your home from escaping outside. When you invest in underfloor insulation, you’re investing in a year-round solution to better temperature regulation and energy efficiency.

Can Underfloor Insulation Cause Problems?

When thinking about whether floor insulation is worth it for their house, many people wonder if it will cause problems with moisture. Common questions include:
  • Can under floor insulation cause dampness?
  • Can too much insulation cause condensation?
  • Can too much insulation cause mould?
Regardless of whether you have insulation or not, your home can be prone to dampness and mould growth if there is inadequate ventilation and excessive moisture. That’s why it’s important to address these issues before you install your insulation. In an existing home with insulation, especially older homes, it is important to check your underfloor insulation for any damage or moisture retention. If problems do exist, we recommend either removing the insulation yourself, or getting a professional to assist and then addressing the ventilation issues.

Can Underfloor Insulation Cause Condensation?

Underfloor insulation does not cause condensation. However, if you are installing insulation into your underfloor area you must have adequate ventilation. Without appropriate ventilation the air becomes stagnant and moisture trapped, which can lead to dampness and mould growth. Planning ventilation in your underfloor area is important and can be as simple as installing small vents on the surrounding walls of your basement area. This promotes air movement through your underfloor area and can also minimise the risk of mould growth. Ensuring adequate ventilation in your entire home is also important and we recommend talking to your builder if you are planning to install a whole-building ventilation system.

How to Make the Most of Your Insulation Investment

Follow these tips to get the best return for your investment:

1. Choose the right type of underfloor insulation

The design and age of your home will affect what type of insulation you use under the floors. For the best performance and durability, choose high quality products from reputable brands. Bulk insulation (such as rolls and batts) is a good choice for raised timber floors or suspended floors where there is subfloor access. Rigid foam boards are ideal for insulating concrete slabs and can also be installed under the floor finish if there is no sub floor access. Two popular options for under slab insulation are Foilboard Slabmate and Slabmate Pro. Find out more about the best underfloor insulation for Australian homes.

2. Upgrade to a higher R Value

The R Value of an insulation product tells you how effective it will be at preventing heat loss and gain. The higher the R Value, the more effective it will be at insulating your home. At Pricewise Insulation, we recommend installing a minimum of R2.0 for underfloor applications in areas like Perth, Brisbane and northern NSW. For cooler climates, such as Sydney, Adelaide and Melbourne, we recommend a minimum of R2.5. If your budget allows, you may wish to upgrade to a higher R Value for better performance.

3. Calculate how much you need

It’s important to calculate how much insulation you’ll need for your project to avoid underbuying, overbuying and waste. Simply measure the length and width of the area to be insulated and multiply them together to get the required metres squared (m2). Floor insulation batts are available in a range of widths suitable for most Australian homes. You will need to measure the width between your floor studs to determine which size you need. The batts should fit snugly between the floor joists without being compressed. Use our insulation calculator to plan for your project.

4. Follow installation guidelines – or get a professional installation

Underfloor insulation needs to be installed correctly in order to work properly. If you are installing the insulation yourself, watch our DIY instructional videos before starting. Alternatively, book a professional installation service to ensure a high standard job. A professional insulation installer can also advise you on the best type of insulation materials and methods of insulating for your home.

Can You DIY Underfloor Insulation?

Installing underfloor insulation yourself can be a great way to save money on installation costs. It’s not too difficult to install underfloor insulation, provided you have the time and safe access to your underfloor area. The best time to install insulation is during the building phase of a new home, but it is possible to install or “retrofit” floor insulation in older houses. Be sure to do your research before starting the installation and watch our DIY instructional videos for more information.

So, Is Underfloor Insulation Worth It?

Whether you’re building a new home or thinking of installing insulation in an older house, don’t overlook the power of floor insulation to improve your home’s energy efficiency. Along with ceiling insulation and wall insulation, underfloor insulation is one of the most effective ways to cut down your energy consumption and save money on your power bill year round. Get started today with our range of high quality, affordable underfloor insulation products.

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From $ 19.57 p/m2 inc. GST

11 thoughts on “Underfloor Insulation: It Works, and It’s Worth Its Weight in Gold

  1. Susan says:

    I am insulating the walls on my own, I an thinking the green foil will do the job and be easier to handle independently. What are your thoughts?

    • Pricewise Insulation says:

      Hi Susan,

      Thanks for your question! Installing wall insulation batts is a fairly easy process that doesn’t require any prior experience. You can watch our video on how to install wall insulation batts here: https://www.youtube.com/watch?v=09kR5HkoOUg. Foilboard Insulation or foil wall wrap is usually installed in addition to insulation batts. If you want to achieve an optimal R-value then we would recommend a combination of foil insulation and wall insulation batts.

      Feel free to give our team a call on 1300 729 639 if you have any further questions.


  2. Chris Mihail says:

    Hi there I’m looking at insulating under my existing timber floor boards and need to know what would be the best product to install

  3. Kay says:

    A real pity the Greenstuff is not sold in NSW. Very frustrating. Don’t want Knauf. Why ship something from Europe when we should be recycling and producing here in Aus?
    I did all my research and decided on Greenstuf and now find I can’t get it. Why is it not sold in NSW and are there any plans to let us onto the team?

  4. Nat says:

    We live in an old home on stumps with timber floors. We know we need to insulate under our floors, but are worried about creating a pest haven in the insulation eg carpet snakes, rats, mice etc. any suggestions on how to minimise or avoid this?

    • Pricewise Insulation says:

      Hi Nat,

      Thanks for your comment. Neither glasswool nor polyester insulation attract vermin, so you should be OK with either of these options.

      There are also companies that can spray foam insulation to the underside of the floor. This would be the best option but costs a bit more.

      Please don’t hesitate to contact our team on 1300 729 639 or via email at sales@pricewise.com.au if you have any further questions.


    • Pricewise Insulation says:

      Hi Jurij,

      This really depends on the design of your home. If you live in a brick veneer house that has its subfloor area bricked in, the extra efficiency gained from a windproof barrier would be limited. However, if the subfloor is exposed to drafts, installing a windproof barrier under your floor insulation will help assist with the performance of its R-value, as well as help reduce drafts in your home.

      Feel free to reach out if you need any further assistance! Please call 1300 729 639 or email sales@pricewise.com.au.

      Warm regards,

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