Is Underfloor Insulation Worth It? Does It Work?

Does underfloor insulation cause dampness?

Many people understand the benefit of installing ceiling insulation and wall insulation in a home, but what about under the floors? Is floor insulation worth it? Will it really make a difference to temperature control and energy efficiency in your home?

Heat loss and gain can happen anywhere that air can get into your home, including through the floors. Underfloor insulation is designed to slow down the rate of heat loss in winter and heat gain in summer, and prevent air draughts.

Floor insulation will help keep your home more comfortable throughout the year and reduce the need for artificial heating and cooling. In other words, when it’s used along with insulation in the ceiling and walls, floor insulation can help you save money on your energy bills all year round.

How Effective Is Underfloor Insulation?

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%! That means floor insulation could potentially reduce your energy bills by 10% to 20%, which is quite a significant saving.

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 come with warranties of 50 years or more.

How Does Sub Floor Insulation Work?

Simply put, insulation is any material that slows down the flow of thermal energy (heat energy). Normally thermal energy will travel from places of high energy (hotter places) to places of low energy (cooler places) until the temperature is equal everywhere.

This can be a problem if it is a cold day outside and your house loses all its heat or if it’s a sweltering summer day and your house feels just as hot as the outdoors. 

When you install insulation inside your home, it will help slow down the flow of heat, keeping indoor temperatures more comfortable. Insulation also helps your air conditioner and heater operate more efficiently because there is less heat loss or gain.

Read more about the science behind insulation in our article “How does insulation work?

What Is The Best Insulation For Underfloor?

The type and age of your home will affect what type of insulation you use under the floors. Two of the most common types of insulation for the underfloor area are bulk insulation (rolls and batts) and rigid foam board.

Bulk Insulation (Rolls and Batts)

Bulk insulation is a good choice for raised timber floors or suspended floors where there is sub floor access. The batts or rolls should be fit snugly between timber joists and then be strapped or stapled into place. It is important that the insulation is secured in place properly so that it doesn’t drop or sag over time.

Rigid Foam Boards (XPS and EPS)

Rigid foam boards can be installed under the floor finish if there is no sub floor access. They can also be used to insulate concrete slabs. Rigid insulation boards are typically made from extruded polystyrene (XPS) or expanded polystyrene (EPS). They are resistant to moisture and will not sag over time.

What Is The Best R Value For Underfloor Insulation?

To figure out how effective an insulation material is, it’s important to look at the R Value of that product. The R Value represents how much insulating power the product has. The higher the R Value, the more effective it will be at resisting the flow of heat.

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.

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 Much Insulation Do You Need?

Before purchasing insulation materials, it’s important to calculate how much you will need for the project. To do so, you will need to measure the area to be insulated and calculate the square meters (m2). Simply measure the length and the width of the area in metres and then multiply the two together.

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.

Can You DIY Underfloor Insulation?

If you have the time and safe access to your underfloor area, it may be possible to install underfloor insulation yourself. 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.

Although DIY projects can save on labour costs, many people prefer to call a professional insulation installer to make sure the installation is done safely and to a high standard. A professional insulation installer can also advise you on the best type of insulation materials and methods of insulating for your home.

If you are planning a DIY installation you will need:

  • Gloves
  • Staple Gun or Hammer Tacker
  • Tape measure
  • Knife
  • Floor insulation strapping
  • Underfloor insulation batts or rolls

Be sure to do your research before starting the installation and watch our DIY instructional videos for more information.

Is floor 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.

Check out the range of high quality, affordable underfloor insulation products we offer at Pricewise Insulation and don’t hesitate to get in touch if you need advice about thermal insulation for your home.

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3 thoughts on “Is Underfloor Insulation Worth It? Does It Work?

  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.

      Cheers!
      Christa

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