Choosing The Right Insulation For The Job: Which Underfloor Insulation Should You Use?

underfloor insulation

A lot of people overlook underfloor insulation but did you know without it you could be losing or gaining as much as 20% of your home’s heat? Installing underfloor insulation in new or existing buildings is a worthwhile investment that will see many benefits in the long term. Not only will underfloor insulation help you keep your home warmer in winter and cooler in summer, you could end up saving money on your electricity bill. That’s because well insulated homes rely less on artificial heating and cooling to stay comfortable. Underfloor insulation can also prevent air draughts from entering your home through holes and cracks in your floor. Finally, underfloor insulation can also provide acoustic benefits by reducing reverberation noises and dampening the sound of foot traffic. ALSO READ – REASONS TO INSTALL UNDERFLOOR INSULATION.

How Does Underfloor Insulation Work?

Naturally heat energy travels from places of high thermal energy (hot air) to places of low thermal energy (cool air) until there is an even temperature everywhere. This becomes an issue on summer days when that hot air begins creeping into our homes. In winter our lovely warm indoor air can quickly escape through gaps in the floor, walls and ceiling, leaving us uncomfortably cold inside. Underfloor Insulation, like insulation in other areas of the home, works to combat the flow of heat so that you can keep indoors at a comfortable temperature. There are several different types of underfloor insulation which each work to prevent heat loss/gain in slightly different ways. Below we will discuss the best underfloor insulation products and how each of them helps you keep your home warmer in winter and cooler in summer.

Which Underfloor Insulation Is Best?

The most suitable underfloor insulation will depend on a number of factors specific to your situation. For example, are you retro-fitting under an existing house or building a new home? What is the climate like where you live? Are you planning a DIY or will you hire a professional to do the installation? Some of the most common underfloor insulation products include:

Polyester Rolls

Polyester rolls such as GreenStuf Underfloor Insulation are a type of bulk insulation. Bulk insulation works by trapping billions of tiny air pockets in their structure which break up the path of heat, slowing it down. If bulk insulation is compressed during installation it will be less effective. Polyester rolls are made out of recycled plastic materials and come pre-cut to fit new and existing timber joist floors. They are pleasant to handle and have no breathable fibres. They come in a range of thicknesses and R-values, and if you pick a higher R-value or specialised acoustic product you will experience noticeable acoustic advantages.

Buy Underfloor Insulation Rolls - Polyester Insulation

Glasswool Underfloor Insulation Batts

Glasswool batts such as Knauf Earthwool Underfloor Insulation Batts are also a type of bulk insulation which rely on billions of tiny air pockets to slow down heat flow. Glasswool products are a cost-effective option, made 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. They are lightweight and an option such as Knauf Earthwool is pleasant to handle and has none of the itchiness traditionally associated with glasswool. Acoustic options can provide noticeable acoustic advantages by reducing reverberation within the home.

Buy Knauf Earthwool DIY Underfloor Insulation Install - Blog Image

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. Knauf ClimaFoam 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.

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 Green 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.

What R-value Do I Need?

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 high quality products with an R-value of at least R2.0. Remember the higher R-value you choose, the greater thermal benefits and energy savings you will experience.

Does Underfloor Insulation Make A Difference?

Yes, 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. Underfloor Insulation helps create a more pleasant indoor environment which means you’ll probably be using heating and cooling appliances less often. That’s how underfloor insulation can lead to energy bill savings anywhere between 10-20%! Finally, installing underfloor insulation can provide acoustic benefits by dampening the sound of footsteps. Along with wall and roof insulation, underfloor insulation also helps reduce the transfer of noises from outside to inside your home and vice versa.

Video: How to Install Underfloor Insulation Batts

Video: How to Install Underfloor Insulation Rolls

Need Help Choosing The Right Underfloor Insulation?

If you need assistance choosing the ideal underfloor insulation products for your particular situation, why not get in touch with the team at Pricewise Insulation? We have a large range of high-quality underfloor insulation, and would be happy to answer any queries you might have.

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12 thoughts on “Choosing The Right Insulation For The Job: Which Underfloor Insulation Should You Use?

  1. Elisha says:


    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:

    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.


  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.


  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.


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