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.
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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.
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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:
- Knauf Earthwool Insulation
- Bradford Polymax Insulation
- Bradford Optimo Insulation
- Foilboard Insulation
- Kingspan Air-Cell Insulation
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:
- Best ceiling insulation for Australian homes
- Best insulation for your attic project
- Best roof insulation for your home
- Best acoustic insulation for soundproofing your home
- Choosing the right wall insulation
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.