A lot of people overlook underfloor insulation but without it you could be losing or gaining as much as 20% of your home’s heat.

Whether you’re building a new home, renovating or looking for ways to improve energy efficiency, underfloor insulation is a great investment that can help you reap long term benefits.

Figuring out what’s the best underfloor insulation for your project can be tricky, so we’ve put together this guide on the best underfloor insulation products for Australian homes. Find out what products are on offer and how to maximise the benefits while sticking to budget.

What Is Underfloor Insulation and How Does It Work?

Underfloor Insulation, like insulation in other areas of the home, slows down the flow of heat. This helps prevent heat loss in winter and heat gain in summer. Insulation can also have acoustic benefits, reducing the transfer of unwanted noises throughout your home.

Houses that are properly insulated are better at regulating indoor temperatures and rely less on artificial heating and cooling. That’s how insulation can save you money on your energy bills year round.

ALSO READ – HOW DOES INSULATION WORK?

Factors to Consider When You’re Installing Underfloor Insulation

The most suitable underfloor insulation for your project depends on a number of factors such as:

  • Retro-fitting vs installing in a new home. The underfloor space in existing houses tends to be less accessible which may affect which products and methods you use.
  • Type of home and accessibility to the underfloor space. For example, suspended timber floors will require different insulating techniques to slab concrete floors.
  • Local climate. Cold climates may require higher performance insulation whereas warm climates may benefit from reflective insulation.
  • Building regulations. You must comply with regulations in the Building Code of Australia as well as any local building regulations.
  • Underfloor vs mid-floor insulation. Insulating between floors of a multi-storey home has different requirements than underfloor insulation.
  • DIY vs professional installation. Some types of underfloor insulation are easier to handle for DIY installations, while others require expert handling.
  • Acoustic needs. Some insulation products can help manage noise transfer and acoustic quality in your home.
  • Personal preferences and environmental concerns. Preferences for particular material types, brands and sustainability factors may affect your decision.
  • Budget. Check out our guide to the cost of underfloor insulation in Australia to work out how much you’ll need to invest.

What Is the Best Type of Underfloor Insulation?

The most popular underfloor insulation products include polyester rolls, glasswool batts, XPS foam boards and rigid foilboard insulation. Below we explain the features of each type and when to use them.

ALSO READ – CAN YOU USE WALL INSULATION UNDER FLOORS?

1. Polyester Rolls

Polyester rolls such as Bradford Polymax Underfloor Insulation are a type of bulk insulation. They work by trapping billions of tiny air pockets in their structure which slow down the transfer of heat.

Polyester rolls are made primarily out of recycled plastic materials, are pleasant to handle and contain no breathable fibres. They come in a range of thicknesses and R-values.

If you pick a higher R-value or specialised acoustic product you will experience noticeable acoustic advantages on top of the thermal benefits.

Polyester rolls are ideal for suspended timber floors and other types of suspended floors where you can safely access the floor joists. The rolls are fitted snugly between joists and secured in place using straps or saddles.

2. Glasswool Underfloor Insulation Batts

Glasswool batts are a type of bulk insulation which rely on billions of tiny air pockets to slow down heat flow. They can be used throughout the home in walls, ceilings and floors.

Glasswool products are a cost-effective option, made primarily from recycled glass materials. Insulation batts are pre-cut to fit between the joists of timber floors and can be strapped or stapled in place.

Options such as Knauf Earthwool Underfloor Insulation Batts are pleasant to handle with none of the itchiness traditionally associated with glasswool. Acoustic options can provide noticeable acoustic advantages by reducing reverberation within the home.

3. Extruded Polystyrene (XPS) Foam Boards

XPS foam board insulation has a dense closed cell structure which provides excellent thermal resistance. It can be used in a variety of applications throughout a home and is particularly effective in concrete floors as an under slab insulation.

XPS has high compressive strength and is water resistant, which means it can help prevent thermal loss through the ground. It can even be used in multiple layers for higher thermal resistance.

You can retrofit the XPS Board or install it when the concrete is being poured in. A good example of XPS Board is Knauf ClimaFoam and Foamex Insulation.

4. Foilboard Insulation

Foilboard is a rigid insulation panel which can be used in walls and roofs as well as underfloors. They are made from a fire retardant expanded polystyrene core with a pure aluminium layer of foil on both sides. This provides a thermal break and vapour barrier for superior thermal performance and moisture resistance.

Foilboard insulation can be installed quickly and easily and is pleasant to handle as it has no fibres. Panels are easy to cut to fit between the timber joists of a floor and are held in place by floor saddles and joining tape. Foilboard Green is an excellent choice for this type of insulation.

Best Underfloor Insulation Brands in Australia

Australia’s leading brands for underfloor insulation include:

What Is a Good R-value for Flooring?

The R-value of an insulation product tells you how well it resists heat flow. So a product with a higher value will have greater thermal properties than a product with a lower R-value.

For underfloor insulation, we recommend choosing quality products with an R-value of at least R2.0. Keep in mind, you may be subject to local building regulations when it comes to meeting minimum R-Values.

What’s the Best Insulation for Your Floor Type?

The type of floor you have will affect what products and methods you use to insulate it.

1. Suspended Floors

Many older homes are built with suspended floors. If the floor space can be accessed from underneath, you can install insulation batts or rolls between the floor joists and then staple (rolls) or strap (batts) them in place. Alternatively, foil-faced foam boards can be used for suspended floors.

If the crawl space is not accessible, it may be possible to insulate the floors by removing the existing flooring. Draught proofing your floors will also help reduce heat loss and gain.

2. Timber Floors

Suspended timber floors are typically insulated using insulation batts or rolls between the floor joists. In existing homes, this can be done from underneath if there is enough crawl space. Otherwise, you may be required to remove the floorboards in order to access the underfloor area. In new homes, insulation batts and rolls can be installed before the subfloor goes down. This is much easier than crawling under the floor when the house is finished, and is our recommended method!

When batts are installed touching timber floor boards, they can help reduce reverberation and absorb some floor sounds, making your floors sound more solid. For the best acoustic results, we recommend using a specialised acoustic product.

3. Suspended Concrete Floors

Suspended slab floors are concrete slabs that are not in contact with the ground. They are often used in homes that are built on hilly terrain.

Suspended slab floors can be insulated underneath using rigid foam boards or foil-backed rigid foam boards. Insulation batts such as Bradford Optimo Underfloor Batts can also be used on concrete slabs, however care should be taken to manage condensation and moisture issues.

4. Concrete Slabs on The Ground

Concrete slabs that are in contact with the ground are easiest to insulate during the building process. Your Home recommends insulating the sides of the concrete slab, especially if you live in a colder climate.

The underside of the slab should be insulated if groundwater is present. A vapour barrier and foam board can be used before the concrete is poured, while specialised foam boards may be used after the concrete is poured, depending on how much clearance you have.

Does Underfloor Insulation Make a Difference?

Properly installed underfloor insulation makes a significant difference to winter heat loss and summer heat gain in any home. Even if the rest of your home is insulated, the floors can let in air draughts or allow heat to leak out.

Reasons to invest in underfloor insulation include:

  • Better regulation of indoor temperatures
  • Savings of up to 10-20% on electricity bills
  • Reduced electricity usage and environmental impact
  • Acoustic benefits

To experience the maximum benefits of insulation, it’s important to insulate other areas of your home, not just under the floors. Check out our guides to the best insulation for other areas of your home:

Need Help Choosing the Best Underfloor Insulation for Your Project?

If you need assistance choosing the ideal underfloor insulation products for your particular situation, get in touch with the team at Pricewise Insulation.

Browse our large range of high-quality underfloor insulation products, or call our team on 1300 729 639 for expert advice about your project.

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24 thoughts on “Australia’s Best Underfloor Insulation in 2022

  1. Elisha says:

    Hi,

    I was looking at your underfloor insulation range and would like to know which material you advise. We are living in a fibro house with floor boards and have aprox 1m high underfloor space.

    Help would be much appreciated!

  2. Robyn Cunningham says:

    Hello,
    My issue is with moisture coming into the house as the floor is close to the ground in one area. Which insulation would be best? Thank you.

    • Pricewise Insulation says:

      Hi Matthew,

      Thanks for your question. If your minimum access height is less than 500mm then we would recommend getting the insulation installed by a professional, due to safety reasons with wiring and tight confines etc. Please feel free to give us a call on 1300 729 639 if you have any further questions.

      Cheers,
      Christa

  3. Matthew James says:

    Generally speaking, you only need to insulate the ground floor. If you’re on an upper floor, you don’t usually need to insulate your floor space.

    • Pricewise Insulation says:

      Hi Matthew,

      Thank you for your comment. Insulating the ground floor (underfloor) is important for stopping the transfer of heat between the internal and external areas of the home. Insulating the first floor (between floors) is important for reducing the transfer of noise between levels and creating climate zones within the home. We’ve got an article about this here: Insulation for Between Floors. Feel free to give us a call on 1300 729 639 if you have any further questions.

      Cheers,
      Christa

  4. Tony says:

    Hi there, I have a 130+ year old weather house in Sydney (basically looks like a Queenslander after a second story and balconies were added in the 1950s), which is on piers, with height (in the key areas) ranging from c. 600mm to 1100mm. The issue we have is that gaps open in the (kauri) floorboards (and you can even see the dirt on the ground for some of the cracks). We are keep to cut down the draft and put in insulation, so are wondering whether the insulation itself will eliminate the drafts or whether we need to seal the floorboards from underneath somehow first, before installing the insullation. Thanks!

    • Pricewise Insulation says:

      Hi Tony,

      Thanks for your question. Installing underfloor insulation will certainly help reduce draughts and improve the thermal performance of your home. However, we would recommend sealing those gaps first to prevent moisture or dirt from penetrating through the floor and affecting the insulation. If you believe that moisture will be an ongoing issue, then we would recommend installing Bradford Polymax Underfloor Insulation Rolls. These rolls are made from 100% polyester, which means that they won’t absorb any water that comes through the floor when you mop etc. Feel free to give our team a call on 1300 729 639 for a custom quote.

      Cheers,
      Christa

  5. Sayuri says:

    What is the best insulation that thickness must be 5-10mm max for hybrid flooring.. .. would you let me know pls

    • Pricewise Insulation says:

      Hi Sayuri,

      If you only have 5-10mm to work with, then your best option would be to look at a high quality underlay. Obviously these type of products don’t achieve the same thermal performance as slab insulation or underfloor insulation batts, but they are better than nothing. Feel free to give our team a call on 1300 729 639 if you have any further questions.

      Cheers,
      Christa

  6. Zane Ridley says:

    Hi,
    What is insulation would you recommend for a sub floor? Our house is approximately 60 years old.
    I have approximately 350-500mm clearance in most places.
    We live in Geelong, VIC.

    It’s mostly Harwood flooring above.

    • Pricewise Insulation says:

      Hi Zane,

      Thanks for your question. A 350mm – 500mm clearance is quite tight and not suitable for a DIY install, although we do know of professionals that are willing to work in these tight conditions. We would generally recommend installing R2.0 or R2.5 polyester underfloor insulation or R2.5 Knauf Earthwool FloorShield Insulation. If there is a potential for water to seep through the cracks in the hardwood flooring, then we would recommend the polyester option as it does not absorb any water.

      Feel free to contact us if you have any further questions.

      Cheers,
      Christa

  7. John says:

    The width between our joists ranges from 300mm to 450mm. Can 430mm batts be squeezed in or better to use polyester rolls?

    • Pricewise Insulation says:

      Hi John,

      Thanks for your message. Glasswool insulation products such as Knauf Earthwool and Bradford Optimo can easily be cut to size. They come in 450mm widths to suit 430mm joists, but can be cut to 320mm wide to fit 300mm joists. The batts should fit snugly between the underfloor joists so they don’t fall out of place, but they shouldn’t be compressed as this will affect their thermal performance. You can watch our tips on how to install Bradford Optimo Insulation here: https://www.youtube.com/watch?v=HDOA7aiIeOs.

      Alternatively, you could purchase 450mm polyester rolls and staple these between the joist as shown in this video: https://www.youtube.com/watch?v=ZzQZ8go0WME. Feel free to give our team a call on 1300 729 639 if you have any further questions.

      Cheers,
      Christa

  8. Erin says:

    Hi, I want to install myself under floor insulation in my weatherboard house with floorboards. There is about 500mm height clearance. Moisture could also be an issue, also which is the best from a sustainability perspective? We live in Melbourne.

    • Pricewise Insulation says:

      Hi Erin,

      Thanks for your question. If moisture is a concern then we recommend installing Autex GreenStuf Underfloor Insulation or another polyester insulation product. Unlike glasswool, polyester does not absorb any water.

      All Autex GreenStuf products are manufactured using 100% polyester fibre and contain a minimum of 50% previously recycled fibre (from PET plastic). Glasswool insulation products such as Knauf Earthwool are made using recycled glass, so this is not to say that polyester is more sustainable than glasswool.

      Given the low clearance of only 500mm, you might want to consider getting a professional insulation installer to assist with the project.

      Cheers,
      Christa

  9. Fred Scott says:

    Hello,
    I have a 30 year old house on stumps, recently renovated with new spotted gum floor boards now showing signs of capping from moisture coming up from the ground. I have some under floor fans in place at the moment but am interested in under floor insulation to stop the moisture transfer. Space under bearers varies from 1 meter to 300mm. About 10 percent of the floor area has less than 400mm clearance to the ground. Could you please recommend a suitable product to use, and an installer in the Berwick area, kind regards, Fred Scott

    • Pricewise Insulation says:

      Hi Fred Scott,

      Thanks for your comment. If you are having such big moisture issues then we would recommend getting spray foam insulation installed in the underfloor area. We recommend using a closed cell insulation to create a moisture barrier.

      There are a couple of companies in Melbourne who install spray foam and it’s a service that EcoHome may offer in the future.

      Cheers,
      Christa

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