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UFH Can Easily Be Installed In Existing Buildings

Rex Ingram, of Timoleon, says there is a misconception that underfloor heating can only be installed in new buildings:

IT IS well known that underfloor heating (UFH) is the most comfortable form of heating, completely unobtrusive making best use of space, safer and more hygienic, and that the right form of UFH is the best way of using renewable energy.

However, many think that UFH can only be installed as pipe set into a screed or concrete floor. Consequently, for them, it is impossible to consider UFH in a refurbishment project because this would mean digging up existing screed floors.

Yet it is possible to easily install effective UFH when refurbishing a building, and there are several different ways of doing this.

One option is to install UFH as a thin overlay. Another is to remove a worn-out timber floor deck and then install UFH with a new floor deck.

Overlays: A variety of thin UFH overlays are now available which can be set over the top of an existing structural floor – concrete or timber. The heating pipe is incorporated within the thickness of the overlay.

Most of them increase the floor height in total by no more than 20-30mm. To put this into context, when you measure the gap beneath the sweep of the main door leading into a flat or a house, frequently it is 30-35mm.

Even where the gap is less than this, it is possible to create a mat well below the sweep of the door, and then install an UFH overlay up to the edges of the matwell. The lower edge of internal doors can be trimmed using the type of saw attachment often used by carpet fitters, without having to remove them first.

Overlays are made from various materials – for example, timber, rigid insulation, compressed gypsum – and they can be topped off to suit different applications all within the 20-30mm build up. You can use 6mm ply or MDF if laying carpets, 6mm gypsum if laying tiles or stone, or thin hardwood laminate.

In fact, if you glue a good-quality thin timber laminate across the top of a timber UFH overlay you can create a 21-25mm thick glulam providing the same high underfoot-quality as an expensive full thickness hardwood floor, and far higher quality than from installing the same laminate on its own. In the process, cost savings associated with using a timber laminate instead of solid hardwood can pay for the UFH.

In flats with concrete floors, impact-sound transmission from the floor of one flat down into the flat below can be absolutely dreadful – the neighbours suffer every stiletto step or chair drag. If an UFH overlay is set onto 3mm acoustic foam before installation, the improvement in impact sound transmission can be enormous with marginal increase in build-up height.

Due to the proximity of the pipe to the floor surface, an UFH overlay can provide effective heating while using much cooler water than other forms of UFH, making an overlay ideal for use with heat pumps, for example. Overlays also have low thermal mass enabling them to warm up very quickly – not a feature normally associated with pipe-in-screed UFH. Overlay UFH is even being used in Grade 1-listed buildings because it can be removed in 100 years and won’t leave even one screw-hole in the original building.

For those able to accommodate the drying- time involved, a heating pipe can even be incorporated within a thin self-levelling screed set over an existing structural floor.

Suspended timber floors: If you are faced with an old planked timber floor deck, where the planks might have been lifted several times during the building’s history, and they have split ends and are generally in poor condition, they can be removed entirely, the joist spaces can be cleared of previous generations of wiring and old plumbing, and then filled with acoustic insulation.

There are then several different forms of UFH which can be installed before a new timber or gypsum-plank floor deck is put in. The result is a floor that will have been thoroughly inspected, can be treated with timber preservative while the floor deck is up, and which ends up with greatly improved acoustic performance

plus UFH.

There are two forms of UFH which work very well in this situation. The best of these has the heating pipe incorporated within the thickness of the new floor deck because it is very responsive while using the lowest water temperatures of all. The other uses channelled and foiled panels of rigid thermal insulation which are supported between the tops of the joists, in such a way that the foiled top maintains close mechanical contact with the underside of the new floor deck.

Some installers still nail rigid UFH diffuser plates between the tops of joists but this form of UFH is much less effective than the first two forms because it requires sufficiently higher water temperatures that it is not best-suited for use in association with some heat pumps.

The worst of all forms of UFH are those in which UFH pipes are used to heat an air-space beneath the new floor deck because these require very high water temperatures to provide effective heating, and the hot dry air pockets they create have the potential to dry-out the floor deck.

This article has been reproduced from the Contract Flooring Journal website. You can find them at