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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 has to 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 has to 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 Isolation be Positioned? 

All isolation should be installed below the concrete slab, according to the latest building regulations. The prevent downward heat loss, and it may also be a good idea to include isolation directly below the warm water pipes.   

How Much Insulation is Required? 

For underfloor heating, 100mm of PIR insulation will work just fine. Keep in mind, however, that you may have to change this to stay within the U-Value limits. Since underfloor heating products differ, this means that you should make sure that you use the correct PIR insulation to remain within these limits.   


To ensure that you install optimal isolation for your wet underfloor heating, head over to SuperFOIL to discuss your insulation and heating needs with them. Before adding insulation, make sure that you only consider high-quality products that adhere to the building requirements. Also, make sure that you stay within the U-Value limits after you have installed your wet underfloor heating units.

Try to adapt your wet underfloor heating to your existing or planned flooring to ensure that you get the best background heating.