Underfloor heating: a modern phenomenon?

Underfloor heating: a modern phenomenon? from Instarmac Group

By: Instarmac Group  14/09/2011
Keywords: flooring, flooring products

 

Few of you will be aware that 2000 years ago the Romans actually realised the benefits of having an underfloor heating system of which Chester has a fine example

There are two principal types of underfloor heating (UFH) systems available in today’s market – warm water pipes and electric matting.  UFH is getting increasingly popular due to a string of benefits (discovered by our Roman conquerors all those years ago) such as energy saving, cost cutting and the fact that the heat encompasses the room and its occupants.  Add to this the potential to remove radiators enabling a more flexible furniture layout and improved health & safety, UFH is now being utilised in a variety of environments from homes to offices to schools to hospitals.  As far as flooring manufacturers, and more importantly flooring contractors, are concerned it is important to familiarise ourselves with these various advantages.

Simply the efficiency of UFH is due to the principle that heat rises.  When heating a room by conventional methods such as radiators, heat is lost as it travels around the room.  In comparison, heat from underfoot rises through the room warming all in its path with consistency, and virtually eliminating wasted heat and energy.

Substantial numbers of new build properties are incorporating warm water pipe UFH and various refurbishment and extension projects now include radiant electric matting in their design. 

It is important to be aware of the pitfalls of warm water pipe UFH systems, as well as the benefits.  Don’t worry!  They are not severe, but as in most cases a lack of understanding and knowledge can result in repercussions.  It’s in everyone’s interests to follow simple principles to avoid such.  

When you are told that UFH is within a screed you are asked/contracted to lay onto, as a flooring contractor you should ask if the system has been fully commissioned as stated in the British Standard Codes of Practice and the CFA (Flooring) Installation guide.

You will often be told that the UFH has been checked and it is fine…ask again!  Often the main contractor will get the system pressure tested for leaks and will claim it has been commissioned...it has NOT. 

Poor design or installation of the UFH system may also pose a challenge for flooring contractors. 

Correctly installed screeds with warm water pipe UFH should include expansion strips (not to be confused with the wider expansion joints found in concrete subfloors) which should be visible

Expansion strips should be around all perimeters and upstands as well as in door thresholds.  They should also be located between the different zones of heating pipes (ones are individual areas/rooms that have their own heating controls).

If both commissioning and design are checked before flooring installation commences then warm water pipe UFH poses no problems to fitters. 

Electric matting, better known as ‘under tile heating’ (UTH) is now used for different coverings as well as tiles.

UTH is relatively straight forward in its make up; electric currents run along cables (usually bound together by matting), heating all that surrounds – originally designed for ‘cold’ tiled floors to be warmed,  meaning more comfortable living areas.  It is now most commonly found in refurbishment, conservatories and extension projects.  Due to its increased simplicity, energy-saving and ease of installation it is now being utilised for other floor coverings and even being recommended as a primary heat source.  There is a great deal of choice in the UTH market but don’t let this confuse or panic you, as requirements will usually be specified by the designer/client.

The output of the system is typically 100-200 W/m².  Generally, the higher the wattage then the more likely a problem is to occur if installations are not carried out correctly.  The incorporation of insulation materials to get maximum effect from the UTH means that loading on the flooring has to be considered, particularly with flexible floor coverings, to prevent indentation.  Skimping on the smoothing compound application is a very risky step and is one piece of advice that I hope you don’t dismiss.

As a flooring contractor the ideal scenario when commissioned to complete a project that incorporates UTH is to arrive on-site with it installed.  Plain and simply as the flooring contractor your remit should be to prepare the floor and apply the requested floor covering in a professional manner.  This will normally be a case of applying a primer, suitable smoothing compound and recommended adhesive.  The Tile Association recommend that: “All electrical work must be carried out by a Part P competent person/electrician or certified electrician and in accordance with Part P Building Regulations. 

Electrical Safety 2005.” If this is the case, seek certification, and then proceed with installing the floor covering. 

Considering the above, I do not recommend that a flooring contactor gets involved in installing the UTH itself, however there may be an opportunity to get involved in the installation of insulation materials. 

If stone, ceramic or other similar tiles chosen, the normal process is to smooth the floor just to cable height.  This is simply to enable the tile adhesive, which is applied by a notched trowel, not to snag and drag on the cables.  The normal smoothing compounds to use would be latex or fibre-reinforced, but high polymer water mixes may also be appropriate.  Don’t forget the use of a primer first to ensure adhesion is at its optimum. 

If it is resilient flooring or a carpet that is being installed it is essential to cover over the cables with sufficient smoothing compound so as not to crack and break up under the temperature fluctuations that will occur.  A typical recommendation would be for a minimum 3mm over the cable with a fibre-reinforced product or a minimum 5mm over the cables with a high performance latex.

The next stage is adhering the floor covering.  The adhesive choice for bonding the specific floor coverings may be listed in the specification, but if not then it is strongly advised to seek out a High Temperature Grade adhesive (HT) for vinyls, linos, carpet etc.  Always use a flexible tile adhesive if you are fixing tiles.

The advise above will help ensure that  a floor laid well, will stay laid well, even under the abuse that is often encountered with UTH i.e. end users suddenly cranking up the heating when they return in from a weekend away.  Or leaving dense heavy materials over the floor resulting in a locallised heat build up

The choice of primers,  smoothing compounds, adhesives, cementitious tile adhesives etc. are all there to help minimise any failures and can accommodate a level of abuse by end users…but don’t tell them!

To read a full in-depth version of this article, please visit or call 01827 871871 to request a copy.

Ultra Floor is part of the Instarmac Group plc

Keywords: flooring, flooring products

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