Combine Insulation Upgrades with Underfloor Heating for Maximum Impact
Tired of cold spots and high energy bills? Insulation could be the missing piece in your underfloor heating setup.
When laying insulation for underfloor heating, you’re not just speeding up heat-up time—you’re improving comfort, reducing waste, and getting more from your system. In this article, we’ll explain how underfloor heating insulation works, the benefits it brings, where it should be installed, and how to fit it correctly for different floor types including timber, concrete, and wet rooms installations.
Key Points:
Insulation boards help prevent heat loss and reduce running costs.
- They’re easy to cut and install under most floors, including concrete and timber.
- Wall use is possible, especially in wet rooms and bathrooms.
- Skipping insulation can double or triple your heat-up time.
- We’ll explain how to install boards properly, step by step.
The 3 Main Benefits of Underfloor Heating Insulation
- Lower Energy Use
One of the biggest advantages of using underfloor heating insulation is that it helps reduce heat loss through the subfloor. This means your underfloor heating doesn’t have to work as hard to maintain a comfortable temperature. By keeping more heat where it’s needed—inside your home—you’ll use less energy over time, which can lead to noticeable savings on your heating bills.
- Warmer Rooms, Faster
Insulation for underfloor heating helps push heat upwards instead of letting it sink into the ground. This makes underfloor heating systems much more responsive. Whether you’re heating a living room, kitchen, or bathroom, rooms warm up quicker and hold heat for longer. The result? A more comfortable home with fewer cold spots.
- Less Noise Between Floors
Laying insulation for underfloor heating can also help reduce noise, especially in multi-storey homes. By adding a layer of insulation between floors, unnecessary sounds from footsteps and other activity is lessened, making spaces quieter and more relaxing.
Read up on other efficient ways to save energy when renovating your home.
What Are Underfloor Heating Insulation Boards?
Underfloor heating insulation boards are fitted between the heating element and the subfloor. Their main purpose is to stop heat from escaping downwards, so more warmth rises into your home. This helps improve the overall performance of the system—particularly for electric underfloor heating.
These boards are typically made from a dense, water-resistant polystyrene core, finished with a fibreglass-reinforced cement coating. They’re strong enough to support floor finishes, while still being lightweight and easy to handle. No priming is needed before tiling, which makes installation quicker.
You’ll find them in a range of thicknesses from 6mm to 50mm, giving you flexibility depending on the floor type and room size. Thicker boards tend to offer better insulation, but even the slimmer options make a big difference.
Did you know that, without proper insulation, floors over concrete can take 2–8 hours to warm up? However, with insulation boards, that time drops to just 30 minutes–1 hour—saving time, energy, and money. Learn more in this guide on how long does underfloor heating take to warm up.
Where Else Should You Consider Adding Insulation?
While laying insulation for underfloor heating is a smart move, it’s not the only area in your home where heat can escape. Adding extra insulation in key locations can reduce overall energy use, improve comfort, and take the pressure off your heating system.
Walls – No matter whether it is an old or new build home – walls are a common culprit in heat loss. You can insulate cavity walls by injecting foam or beads into the gap. For solid walls, insulation boards can be added internally or externally to help trap heat indoors.
- Windows – Single-glazed windows are a common source of heat loss. Replacing them with double glazing is one of the best long-term solutions. For a quick fix, stick-on window film or thermal blinds can also make a difference.
- Doors and Door Frames – Even small gaps around doors can let warm air escape and cold air in. Fitting weather stripping or using draught excluders can help keep rooms warmer. You can also upgrade to doors with built-in insulation if needed.
- Ceilings and Lofts – Because heat rises, a large amount of warmth can be lost through the ceiling. Adding insulation above the ceiling—especially in lofts—can prevent this. In some homes, up to a quarter of heat loss comes from the roof area.
Can You Install Insulation Boards on Walls?
Yes, you can. Some types of underfloor heating insulation boards can also be used on walls. This is particularly useful in wet rooms and bathrooms. Thanks to their waterproof surface, they’re ideal as tile-backing boards and can even support wall-mounted heating systems.
Just make sure the joints are sealed properly. Once that’s done, you can tile directly over the boards or apply them as part of a heating setup for full coverage warmth.
How to Install Insulation Boards
Before laying insulation for underfloor heating, it’s worth planning out the board layout first. Think about the room’s shape, any obstacles, and where your heating cables or mats will go. Once you’re happy with the layout, use a sharp retractable knife to cut the boards to size.
Make sure the subfloor is clean, dry, and free from any leftover adhesive or debris. A smooth, stable surface helps the insulation sit flat and stay in place. In wet areas like bathrooms or wet rooms, always seal the joints and any screw holes using the right sealant as specified by the product manufacturer.
How to Insulate a Floor Over Concrete
Concrete bases need to be fully cured before you start. Once the concrete is ready, apply a multi surface primer to prepare the surface.
Use a flexible floor adhesive and a 4mm notched trowel to fix the boards to the concrete. Lay them in a staggered pattern—like bricks—making sure there are no gaps or air pockets underneath. Tape the joints with glass fibre tape for a secure fit.
For areas that require waterproofing, follow up by sealing all joints using the correct sealant recommended by the insulation board manufacturer.
Installation on Timber Floors
Start by checking that the timber floor is stable and level. If needed, use a latex self-levelling compound to smooth out uneven areas.
Fix the boards down using screws and washers—12 screws per board, spaced in three rows of four. The washers should sit flush with the surface of the board.
Wet Room Installation
For wet rooms, you’ll need to apply a self-levelling compound, especially with water underfloor heating kits. This layer should be at least 3mm deep before installing your final floor covering.
Always follow manufacturer instructions when working with underfloor heating insulation systems to make sure everything performs as expected.
In conclusion, installing underfloor heating insulation is one of the simplest ways to improve system performance and cut down on wasted heat. Whether you’re laying insulation for underfloor heating over concrete, timber, or in a wet room, the right boards can make your home warmer, faster, and more energy-efficient. With clear benefits like quicker heat-up times and lower bills, taking the time to insulate properly is well worth it—especially when combined with the right fitting method for your floor type.
Looking to install underfloor heating yourself? Try these DIY underfloor heating tips.
FAQs
Can I reuse underfloor heating insulation boards if I remove the flooring?
In most cases, insulation boards are not reusable once they’ve been fixed in place, especially if they were secured with tile adhesive or screws. Removal can damage the boards, reducing their effectiveness. It’s usually better to replace them during any major floor renovations.
How thick should underfloor heating insulation boards be?
The thickness depends on your floor type and available height. Common sizes range from 6mm to 50mm. Thinner boards are useful in rooms with low ceilings or minimal floor build-up, while thicker boards offer better insulation over concrete or uninsulated subfloors.
Is it worth insulating small rooms like en-suites or hallways?
Yes—smaller rooms lose heat quickly, especially through floors. Laying insulation for underfloor heating in these spaces means quicker heat-up times and better temperature control, which is useful in areas used regularly but for short periods.
Sources
Gibbs, J., (2025) Top energy saving upgrades to make if you’re renovating your home. Energy Saving Trust. [online] Available at: https://energysavingtrust.org.uk/energy-saving-upgrades-for-home-renovation/ [accessed 30/07/2025]
About the Author – Jack Poyser
Jack’s participation in the UFH industry began in 2020. Underfloor heating systems are something he truly believes in, and he very much enjoys the designing of customers’ systems to fit their bespoke needs. Contact Jack today to discuss your bespoke underfloor heating kit by calling 01625 324345 or email info@underfloorheatingtradesupplies.co.uk.