Getting the right insulation for wet underfloor heating


Wet underfloor heating consists of a system of pipes that is heated by means of a boiler into the floor. As an alternative to electric systems, wet underfloor heating is the more affordable option in the long-run as it runs at around 6p per kWh where electric heating can cost 13 per kWh. It is for this reason that many people prefer this type of underfloor heating.

Wet underfloor heating can only reach these levels of energy efficiency, however, if it is properly insulated. This will reduce additional heating costs and provide the interior space with comfortable background heat. In order to install the best insulation for your wet underfloor heating system, let’s consider some of the most common insulation questions for wet underfloor heating.

Common Questions

Which Flooring Materials are the Best?

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 it 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.

How to Prevent Movement?

Since all material expands 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.

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 regs, dependent 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. SuperFOIL can help reduce the overall thickness of the build-up to assist with matching floor levels, or door thresholds etc.


To ensure that you install optimal insulation for your underfloor heating, head over to SuperFOIL to discuss your insulation and heating needs with them. Before purchasing insulation, choose high-quality products that adhere to the building regulation requirements. Also, make sure that you meet the U-Value requirements after you have installed your underfloor heating system.


Our FREE guide gives you all the information on saving time and money when insulating your home, and how to really make a difference to the comfort of your rooms.

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SuperFOIL Insulation Guide