Does Underfloor Insulation Make a Difference?

Out of all the heat that is lost during the cold winter months, most of it escapes through the ceilings and walls. A small portion, however, will also inevitably make its way through the floor. Is it enough to warrant an insulation investment? Does floor insulation make a difference? These are questions that many home owners are faced with at the time of construction, particularly if they are trying to make ends meet and come up with a viable and balanced building proposal and budget. People living in homes with a raised timber floor may also find themselves wondering the same thing, especially if they’ve been through a few hard winters.

Underfloor Insulation Undoubtedly Has Its Place

As far as thermal efficiency goes, wall and roof insulation are by far the most popular home insulation products, and not without good reason – combined, the roof and wall areas probably account for over 70% of a building’s heat loss. But underfloor insulation also has an important role to play. These days many new homes will have a layer of polystyrene insulation lying underneath the slab. The reason this is often used under concrete slabs is because it has an exceptional compressive strength. Homes with raised timber floors may have layer of bulk underfloor insulation.

Honest Feedback from Recent Pink Batts Insulation Customer

Pricewise Insulation recently contacted a customer who purchased Pink Batts underfloor insulation, to be installed by a professional insulation installer. Interested in some honest feedback on the outcome, Pricewise conducted an interview on the whole experience. Following is a summary of the interview:

Q: What made you decide to invest in underfloor insulation?

A: The house we’d moved into had a raised underfloor, and it was quite chilly to walk on even when the rooms were warm. That, together with the fact that we’d done some research and knew that underfloor insulation can help to reduce our energy costs resulted in our decision to go for it.

Q: How did you experience the process of getting the insulation delivered and installed?

A:  This was actually quite easy. We knew a good insulation installer, so we measured up the floor area, ordered the insulation to be delivered to our door, and booked the installer for the following day. It took him less than a day to insulate the entire underfloor area.

Q: Did the underfloor insulation make a difference?

A:  Definitely. Most of the internal heating in our home comes from the wood combustion heater in the living room. This creates a lot of heat and the lounge room and adjoining rooms are comfortably warm while it’s on. But what was interesting to note was the difference in floor temperature from close to the heater and further throughout the house. Close to the wood combustion heater, the floor quickly warmed up and remained warm. However, in the rooms furthers from the source of heat, the floor was noticeably cooler, despite the insulation. Presumably, if we had heaters running in those rooms also we would have noticed a similar effect to the main living area.

So, How Much Difference Does Underfloor Insulation Make?

Underfloor insulation does make a difference. Although it is not a replacement for a heater, where heaters are in use, it definitely helps to ensure that as little heat as possible escapes through the floor. The table below shows the effect underfloor insulation and heat sources may have on the temperature of the floor.

The Potential Effect of Underfloor Insulation and a Heat Source on the Floor Temperature

As you can see, it’s the combination of underfloor insulation and a heat source within the room that creates a floor that is comfortably warm. The absence of either of these will result in a floor that is cool to touch, and without either of them the floor will be uncomfortably cold.

There is no doubt that if other areas of the room – walls, doors, windows, ceiling – are uninsulated, this will have a further impact on the temperature of the floor.

12 Most Common Questions About Underfloor Insulation

At Pricewise Insulation we get a lot of questions about underfloor insulation. We’ve collated the most common ones and created a go to page where all your questions about underfloor insulation are answered.

1. Does Underfloor Insulation Work?

Yes, underfloor insulation definitely works and is commonly used under raised timber floors. Regardless of whether you’ve got carpet above the floorboards, underfloor insulation is still necessary to reduce heat loss and to maintain a comfortable floor temperature.

2. Is it Worth Insulating Under Floorboards?

Yes, it is. Underfloor insulation reduces heat loss, keeping you warmer in winter. Underfloor insulation makes a noticeable difference, particularly when you’re not wearing shoes inside, and in areas where you spend a lot of time sitting or standing. As underfloor insulation reduces heat loss, it also contributes to reducing energy consumption in the home.

3. How Effective is Underfloor Insulation?

If you currently have no insulation under your floor, then even putting a minimum R-value of thermal underfloor insulation will effectively reduce the transfer of heat. The extent to which the underfloor insulation reduces heat loss will depend on the following factors:

1. The r-value of the underfloor insulation.
2. How correctly it’s installed. The performance of even the best underfloor insulation will be greatly reduced if it is installed with gaps throughout. Similarly, insulation which is compressed beyond its optimal thickness won’t perform as well as correctly installed insulation.

4. Can you Use Ceiling Insulation Under the Floor?

This is not an uncommon scenario. Similarly, you might want to know if you can use wall insulation in the under floor. Maybe you’ve finished installing the ceiling or wall insulation and you’ve got some leftover bags. You’re justified in thinking that they can be used in the underfloor, rather than spending money on officially branded underfloor insulation. Perhaps you weren’t even thinking to insulate the underfloor, but now that you have some leftover bags, why not?

Technically there is no reason why ceiling and/or wall insulation cannot be installed underneath the floorboards between the floor joists. However, this is not to be recommended. Both a standard glasswool and polyester ceiling and wall insulation segment is a lot less rigid than the corresponding floor insulation product. This means that a lot more effort (and strapping/tape) will be required in order to keep the insulation in place and get a satisfactory result. Even then it will be difficult to get a tidy finish especially if the underfloor is exposed to wind and weather.

5. Do you Insulate Floors?

Is floor insulation necessary? Yes, in New Zealand underfloor insulation in rental properties, where it is reasonably practicable to install, is a requirement under the Residential Tenancies Act.

6. Should I Insulate Between Floors?

Insulating between floors, ie the midfloor, has two key benefits. One is sound reduction. Without insulation, the sound of conversations, music, tv etc. will easily be heard between floors. The typical gap between the lower floor ceiling and the upper floor floorboards is more than adequate to fit a good layer of thermal insulation, or even better, high density acoustic insulation, which results in the above-mentioned household sounds becoming barely audible.
The other benefit is climate control. By insulating between floors, you’re better able to isolate heating or cooling to either level of the home, helping to reduce energy costs.

7. What is Underfloor Insulation?

Underfloor insulation is thermal and/or acoustic insulation which is typically installed between the joists of raised timber floors. It can be made of polyester, glasswool or other materials with insulating properties.

8. How Does Floor Insulation Work?

Floor insulation works by providing a thermal barrier between the room above the floor and the outside air. This is necessary because the materials used in common flooring – timber floorboards, ceramic tiles, laminate etc – usually have very poor insulating properties.

9. How Much Heat is Lost Through the Floor?

Heat loss is difficult to quantify, but energy savings are definitely measurable, and obviously there is a correlation between heat loss and energy consumption. As a rough guide, in a fully insulated home, the total energy savings can be attributed approximately as follows:

Ceiling: 40-50%
Walls: 20-30%
Underfloor: 10-20%

10. How Much Does Underfloor Insulation Cost?

Underfloor insulation costs between $7.88/m² and $17.32/m², depending on the brand, type and R-value. Visit our insulation calculator page to work out how much insulation you’ll need.

11. What is the Best Underfloor Insulation?

Autex Greenstuf underfloor insulation is one of the best insulation brands on the market. It is entirely itch free and contains no breathable particles. It is easy to install and can be expected to last as long as your home.

12. How is Underfloor Insulation Installed?

Greenstuf underfloor insulation is fixed up to the floor joists and stapled to the side of the joists to ensure that it remains in place.

Earthwool, Pink Batts and Bradford underfloor insulation is also installed between the floor joists. However, strapping or taping is used to keep it in place. Check out our DIY Home Insulation Tips for more details on how to install underfloor insulation.