Do I need to insulate with a retrofit system?

by UFH1

This is one of the most common questions are asked by customers retrofitting underfloor heating (UFH).

As UFH designers/suppliers/installers, we would recommend insulation in every case and, not just in the floor. We design systems to produce more than enough heat output to satisfy the needs of any property, however it’s the insulation in the property that keeps that heat in where it’s required!

In the case of a retrofit / overfloor UFH system, the ability to include insulation is usually determined by the floor height available. Retrofit systems are an ideal solution where a ‘conventional’ insulation/screed system can’t be used because excavating the floors or the minimum 80mm-165mm (plus the depth of the chosen floor covering) required isn’t possible. Most applications where retrofit systems are used require a floor depth of between 20mm-50mm (plus floor covering) so by using a 20mm or 25mm board for the UFH pipe there’s not much room for insulation!

The best way to incorporate insulation is to make the best of the floor height available by choosing whichever of our systems suits your needs the best:

It should be noted that both of our systems are designed to be complete space heating solution. What this means is that our systems will adequately heat the areas required without the need for supplementary heating such as radiators/log burning stoves etc

Standard system

25mm XPS insulation board that will insulate the UFH from the floor below and also insulates around part of the pipe.

Premium system

18mm gypsum fibre system that has the highest output/most efficient running temperature of any type of retrofit system on the market. The boards themselves warm up which contributes to the output but could also partly heat what’s below it. With this in mind the options are:

  • Allow the boards to sit directly on the current surface and partly heat the sub floor which, if concrete or similar, will eventually add to the overall thermal mass in time
  • If height is an issue and you don’t want to heat the subfloor at all, use our foil barrier
  • If the minimum height excluding floor covering can be between 24mm and 48mm, use our high density, high compressive strength XPS insulation.


Too much is made of ‘downward heat loss’ with UFH systems. Heat rises and the optimum area of UFH is 1.5-2m from floor level. It’s more important to insulate the walls and ceilings plus incorporating windows with a good u-value than insulate the floor.


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