Getting the right insulation for wet underfloor heating

Wet underfloor heating consists of a system of pipes (heated by a boiler) that circulate warm water underneath the floor of a property.

As an alternative to electric underfloor heating systems, wet underfloor heating is the more affordable option in the long-run. A highly effective means of heating, wet underfloor heating runs at around 6p per kWh – compared to electric which can cost 13 per kWh.

However, wet underfloor systems can only reach optimal levels of energy efficiency if they are properly insulated. When insulated effectively, wet underfloor heating can reduce heating costs and energy bills, provide the interior space with comfortable background heat and offer a seamless solution for heating that maximises useable living space.

In order to install the best insulation for your wet underfloor heating system, let’s consider some of the most common questions about how to insulate flooring effectively.

Common Questions

Which flooring materials are best for wet underfloor heating?

Even though both electric and wet underfloor heating systems can be used successfully with almost all types of flooring, there are certain types that are better for heat output.

Wooden floors can work well, especially since this material is stable under temperature fluctuations. For this type of flooring to work best, it must be less than 22mm thick and should not have a width-to-thickness ratio of more than 4:1. The floor temperature should also not exceed 28 degrees Celsius and the moisture content must be between 6% and 8%.

Ceramic tiles, concrete, and stone will also work well to provide an even background heat with wet underfloor heating.

Will the flooring expand and contract with underfloor heating?

Since all materials expand and contract as they are heated and cooled, the impact heat has on flooring should also be considered. It is essential to include an expansion gap and edge insulation.

The flooring should also be able to expand at a different rate than the screed. The expansion gap can be added at the perimeter of the room and covered by a skirting board with a flexible adhesive to allow for movement.

What are the benefits of using underfloor heating insulation?

Insulating your underfloor heating system provides several benefits, including improved energy efficiency, reduced heat loss, enhanced comfort, and faster heating response times.

The more effective your floor insulation, the more effective your underfloor heating system will also be, as warmth will be directed exactly where it is needed. Underfloor insulation will ensure that heat is directed upwards into the space above, rather than downwards into the ground.

Where should the insulation be positioned?

All insulation should be installed below the underfloor to prevent downward heat loss. On a solid floor, this can be between the concrete slab and the underfloor heating layer or it can be under the concrete slab. In a suspended timber floor, this can be on top of the floorboards, under the floorboards or between the floor joist timbers.

How much insulation is required?

For underfloor heating, a U-value of between 0.13 and 0.25 is typically required to meet current Building Regulations, depending on the type of construction.

To achieve 0.13 U-value performance with a typical rigid foam insulation, it would require approx. 125mm thickness or more. However, multifoil insulation takes up far less space than other insulation products while delivering the same performance.

SuperFOIL’s SFUF multifoil can help reduce the overall thickness of the build-up to assist with matching floor levels, or door thresholds.


The ultimate solution: SFUF multifoil

Designed with solid floors in mind, SFUF offers outstanding performance while taking up far less space than other insulation products such as mineral wool.

Measuring at just 6mm thick, SFUF provides a core R value of 0.8, meaning it can offer excellent insulation for a wet underfloor heating system.

SFUF has been developed with easy installation in mind, making it a convenient solution for everything from DIY installations to large scale renovation projects. Offering exceptional performance and with a lifespan of 50+ years, SFUF is the ultimate solution for underfloor heating systems.

Innovative multifoil for underfloor insulation

To ensure that you use the best underfloor heating insulation for your project, email us at [email protected] discuss your specific needs. Our team will be more than happy to answer any questions you may have and provide you with expert advice.


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