BEAMA

This is a complex subject, but in simple terms underfloor heating is more efficient because:

• it uses lower temperature water (typically 35C to 50C rather than 70C) so less energy is needed to heat the water
• it enables condensing boilers to condense more often
• the nature of the heat (radiant) provides a comparable comfort level at a lower air temperature
• the distribution losses are lower

A wide range of systems are available and each UHMA member promotes their own preferred systems. UHMA members have systems suitable for floor, ceiling or wall fitting; for renovations, extensions or new builds; for domestic or commercial projects; for heating or for cooling or for both; for background heating or primary heating; for mixing with other heat emitters; for all types of heat source; for solid, timber or floating floors.

The range is wide, and whilst UHMA cannot suggest any particular system or application you can be sure our members will be able to give you good sound advice. As useful guidance, vinyl and stone floors provide best underfloor heating performance followed by laminates. Performance is lowered with carpet but of course this will depend on the thickness of the pile.

Building Regulations, together with the new COMPLIANCE Documents L1a and L2a set minimum standards for Thermostatic Control of whole and part systems.

Control systems can be complicated or they can be simple – it all depends upon which UHMA member you choose and what your requirements are.

• Commonly some form of room thermostat is used (usually electronic but sometimes mechanical) which either has a rotary dial, or a digital display.
• Night set-back systems are common, where rather than turning off the system, the thermostat drops to a lower temperature setting. This is generally considered to be more efficient than simple on/off.
  
• Floor temperature sensors can be used especially with electrical systems, but it is worth noting that virtually all warm water underfloor heating companies do not require these.
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• Time clocks and programmers are also used in much the same way as with radiator systems. And fully programmable room thermostats are also a popular option.
• Some UHMA members insist on weather compensation: others don’t.
• Some members offer systems with remote switching via sms or internet connectivity, while others specialise in BMS linked systems.

UHMA members will be able to guide you in your choice and offer suggestions for the best control strategy.

Floor temperature has to be viewed in proper context. Without a temperature difference between the floor and the room there can be no heat transfer, so it is the room heat requirement which to a great extent will affect the choice of floor finish and can occasionally completely change preferences.
 

However the current Building Regulations require such good thermal insulation in construction that only the Renovation projects (old buildings) have to re-consider the suitability of a floor finish.

• BS.EN 1264 Part 2 sets the maximum foot comfort temperature as 29?C
• Part 4 sets floor limits for wet rooms (33?C) and perimeter zone up to 1m (35?C) 
• Vinyl Flooring (standard products) carry a 27?C surface temperature limit
• Linoleum flooring is considered as similar to vinyl with a 27?C surface temperature limit
• High Duty Plastic sheet flooring may be available which accepts a 29?C maximum limit
• Wood floors should normally NOT operate at more than 27?C (moisture dependent) 
• Carpets and Carpet tiles will accept any floor temperature in the range permitted
• Floor covering manufacturers will be able to provide specific information.

Expansion joints are a standard construction detail used with floor screeds in which the underfloor heating is normally embedded. Surprisingly, neither plastic pipes nor electric cables possess the strength or ability to crack a screed which has cured. Any failure will be directly attributable to the screed material and its use. Please check that expansion detailing has been considered by your screed provider.

 
Systems normally include an 8mm expanded polyethylene foam expansion joint around all perimeters of every room to allow for thermal expansion of screed. Additionally an expansion joint is included wherever a Main Building Construction Joint exists, plus across all room doorways, corridor Fire doors, and in awkward shaped rooms over 40 square metres area (longest side 8 metres) to avoid radial cracking, but this does not always apply to Liquid Anhydrite screeds.
 

It is necessary to apply an expansion joint at regular intervals along very long access corridors, and to note that changes of direction can cause additional stress relief joints at relatively short distances
 

Refer to CIRIA Report 184 “Screeds, Flooring & Finishes” and BRE document Floors & Flooring for additional advice on floor screeds.
 

A combined carpet and underlay TOG value up to 1.5 is safe for low temperature systems but values can go up to 3.5 for higher temperature flow. It is common practice to select a TOG of 2.5 or below.  Select an underfloor friendly underlay; your carpet supplier should be able to help. A suggested 5mm of underlay and 10mm of carpet would broadly equate to this but it is a rule of thumb and likely to vary depending on carpet style.

• Water based systems are covered by BS.EN 1264 Parts 1, 2, 3 (Design) and 4 (Installation).
• Electric Cable Systems are covered by BS 1018 ;1971 (Reviewed 1993) mainly for Night Storage systems whilst the newer Mattress and Prefabricated Element systems for under tile or similar systems are covered by EURO-Norm IEC 60364-4 and partly by the Electricity Council Design Guide
• Floor screeds and finishes are covered by BS 8204 (2005) Parts 1-7, BS8203, and DIN Standard 18560 Parts 1-7 – the latter being a longstanding Europe wide reference standard
• Timber floors and timber finishes are covered predominantly by BS 8201 in the UK.

There are a number of visual and manual fault finding actions:

• Check whether the heat source is working correctly (e.g. the boiler or heat pump)
• Check that the circulating pumps are functioning
• Identify whether the controls are calling for heat
• Is the mixing valve working properly?
• Is the room thermostat turned up to the required level?
• If you have a flow gauge check whether it indicates distribution flow
• Check if actuators are working (are they warm when heat is called for?) If not contact an electrician.
   

We recommend in all cases that you should contact your supplier but we are happy to clarify any technical queries where we can.

Yes. There are many companies that supply UFH that do not belong to UHMA, however members of UHMA have to complete a lengthy membership process that helps to ensure that:
 

• The components supplied meet the relevant European and British standards, comply with testing regimes, and have been produced in a quality assured factory to help traceability
• That systems are designed and specified according to the latest updates to the core European standard EN 1264 and the current building regulations and compliance codes
• That systems and components have robust warranties / guarantees that are either insurance backed or are provided by large well-financed businesses.

UHMA members can determine the best system for individual projects across a range of design parameters.
While membership of UHMA does not guarantee a members work, people find it reassuring to know that UHMA members have to have successfully trade in the sector for at least two years before they can join.
If a company isn’t a UHMA member you have to ask yourself “why not?”
 

For a full list of members click here
 

UHMA sets the standards and model syllabus for UFH training, whether for installation, first fix, or design. It has a process for recognising courses.
Currently independent courses are offered by:

• BPEC either through independent training facilities, colleges or manufacturer sites
• Logic Certification 
   

If you want to find out which manufacturers offer training then look at the member micro sites in our membership directory section. Just click on the company name and the micro site appears.