Home > Underfloor Heating - Frequently Asked Questions

Underfloor Heating - Frequently Asked Questions

How does underfloor heating work?

There are essentially two types of underfloor heating system commonly used in the UK, warm water plumbed systems, sometimes referred to as wet or hydronic and the electric underfloor heating systems.

Underfloor heating is used extensively across Europe and has become increasingly popular in the UK during the past couple of decades. 

With an underfloor heating system the floor itself becomes the heat emitter (radiator) and the heating of the room is from the floor up. This is in complete contrast to traditional central heating where the emitters are mounted on the wall and the room is effectively heated from the top down.

Both water based and electric underfloor heating systems are available, they are very similar in the way they produce radiant heat with the obvious difference being the way this heat energy is produced, one uses a resistive heating cable while the other circulates heated water through a pipe system.

Whichever system is used, the heat source is located under the floor and the area to be heated is separated into zones and independently controlled.
The warm water piped systems are generally better suited to new build applications and can be run from eco-friendly  energy sources such as solar panels and heat pumps or more traditional fossil fuels such as natural Gas. Wet systems will require a greater floor build height and a more complex control system than the electric systems and are generally recognised to be have lower running cost. Water based ufh uses water heated to a lower temperature than conventional radiator central heating (typically 50°C rather than the usual 60°C ) which makes it ideal for use with  high efficiency condensing boilers; the lower operating temperature also makes it more viable for use with ground source heat pumps and solar panels.

Electric underfloor heating has gained in popularity over the past decade or so and is particularly well suited to home refurbishment and house extension applications. There are a number of heating types to suit different applications and floor finishes.


How do I know which electric heating system to use?

Electric underfloor heating systems are grouped in to several catergories determined by the type of floor finish you wish to use. The most commonly used floor finish used above underfloor systems would be stone or ceramic tiles, but there are also heating systems for use beneath wood & laminate floors, vinyls such as Karndean and Amtico aswell as carpet.

Tiled floor finish on to insulation board or insulated screed base.
Assuming that the floor to be heated is well insulated beneath the screed it is not strictly necessary to fit an insulation board beneath the heating mats or cables, but, if fitted, will provide a faster heat up time. Under tile heating mats will generally be quicker to install than loose cable heating systems but the cable offers greater flexibility in terms of area coverage. Design will vary from 100w/m² to 200w/m² dependent on floor base heating requirements. Higher output mats can be used as the sole means of heating an area provided base is well insulated and upwards of 85% of floor area is covered.

Tiled floor finish on to timber / plywood base.
All timber floors whether floor boards, chipboard or plywood must be assessed to confirm structural integrity and suitability for tiling prior to installation of electric underfloor heating. Floor boards will require provision of reinforced tile backing boards or plywood before heating can be installed. Heat mats and cables can be fitted directly on to ply-wood and moisture proof chipboard, providing that the floor is treated with a suitable priming solution. Design will vary from 100w/m² to 150w/m² depending on floor base specification. If you are unsure please contact technical support to discuss.

Laminate / Wood Floors underfloor heating.
Laminate and engineered wood flooring can provide a highly effective heating medium with ThermoLAM or Carbon film heating systems. Use with 6mm or 12mm Depron® insulation directly beneath the heating foil. Systems of varying outputs and sizes can be selected to provide full or secondary heating for most areas of your house. Carbon film heating systems are not suitable for use in domestic applications as they do not employ the required earth screen to comply with the IEE 17th Edition wiring regulations. Maximum floor temperature not to exceed 28degree C.

Underfloor Heating beneath Vinyl, Amtico & Karndean floor coverings.
Electric underfloor heating beneath vinyl will require special consideration due to the maximum floor temperature limits permissible and the need to provide a solid surface on which to bond the flooring. The subfloor must be well insulated beneath the screed or by using a reinforced insulated tile backing board such as Marmox. Electric underfloor heating cables (TPP) are then attached to the surface prior to applying two applications of a Latex floor smoothing compound. The first application (4mm) is to embed the heating cables, followed by a second layer (3mm) to put distance between the heating cables and the vinyl to allow heat to dissipate across the floor. Maximum floor temperature not to exceed 28degree C.

Carpets with underfloor heating.
Carpeted floors can provide a challenge for standard underfloor heating systems but the new Crystalline Ribbon Heating System from Primary Heat & Elements are purpose made for this application. The ribbon mat systems are installed directly on to a closed cell insulation material prior to laying the carpet with a low tog (<0.75) underlay. Combined thermal resistance of underlay & carpet must not exceed 2.5 tog.


How do I design my underfloor heating?

Good design and proper specification of your floor heating system is crucial to ensure maximum performance and low running costs. If you have any doubts after reading through our website design pages please call technical support.

Under tile systems (mat)

Heating mats are all 0.5m wide by the required length to cover the listed heating area (eg: 0.5m x 10m = 5m² coverage) so ensure that you have chosen a mat to fit comfortably within your heated floor area. Heat output is determined by the  type of cable used to construct the mats so all cable swill be spaced at around 65mm apart – this ensures a uniform temperature over the heated area. All of our heating mats employ a 100% earth screen to the heating cable and use Teflon insulation, mats are 3mm thick.  Ambient mats are rated at 100w, 150w and 200w per square meter of heating area.

100w/m² mat.  Use for tile warming (secondary heating) applications above timber floors and for wet rooms with rubberised tanking membrane.

150w/m² mat. Use for primary heating of most internal rooms or for secondary heating above insulated screed floors, this is the maximum heat density permissible when laying directly on to timer floors.

200w/m² mat. Use for primary heating for all areas including conservatories, provides the fastest heat up times of all the under tile mat systems.

Under tile systems (cable)

Heating cables are all 3mm diameter and 100% earth screened, they offer a very flexible Installation option for difficult areas or where full coverage is required. Typical heat output ranges 130w/m² (75mm between loops) 150w/m² (65mm between loops) or 165w/m² (60mm between loops).

Foil heater mats beneath laminate or engineered wood floors.

Thermolam is the name we give to our under wood heating system, can be used beneath Laminate, Engineered Timber and some solid wood floors. Can only be used with floating floors and must be used with Depron insulation. Choose a system at least 10% smaller than your open floor area but you will need Depron insulation to cover the entire floor area. Thermolam is rated to 140w/m² and maximum floor temperature for most wood floors should be set to no more than 27 degrees C.


What are the installation basics for electric underfloor heating?

Most electric underfloor heating systems are straightforward to install, assuming that you are reasonably competent at DIY, however all heating electric systems installed in the home must be signed off by a competent electrician under the 2005 part P building regulations. 

Electricians who are affiliated to the NICEIC or ECA would be happy to perform the necessary sign off.

Below are some installation basics to reflect some commonly asked questions but full and comprehensive instructions will be provided with your Ambient heating system.

Electrical requirements will vary from system to system but a few general principles apply, all heating systems in the home must be earth screened and the electrical supply protected by an RCD. Rating of circuit breakers or fuses will be determined by the electrical load of the system being installed. Our technical support team can advise on specific applications or consult your electrician.

All thermostats supplied by Ambient mount in to a 35mm deep single box, all thermostats are supplied with a floor temperature sensor (some systems have two) which must be installed beneath your flooring.

All floor temperature probes are 3m in length.

Cold tail connections (supply lead) to all heating mats and cables are 3m in length.
Larger heating systems comprising two mats require both mat tails to be connected to the thermostat, heating cable can be detached from the mat and run as a loose cable to facilitate this if necessary.

Cold tail connections and floor sensor can be extended if required.


Do Floorwarmers floor heating kits include everything I need?

Yes, all of the heating kits we supply are complete, this means you get everything in one box to install your heating kit successfully.

Includes mats/cable, programmable thermostat of your choice complete with floor temperature probe and conduit housing, SBR floor primers and roller + full installation instruction and warranty certificate.

Do Floorwarmers floor heating mats comply with current regulations?

Yes, all of the heating mats and cables we supply are certified by SEMKO and are CE marked, we do not allow any batch testing, all individual mats and cables are supplied with specific resistance readings. All of the underfloor heating mats and cables we supply are fully earth screened as required by UK 17th edition electrical wiring regulations.

Do Floorwarmers sell through shops?

No, Floorwarmers sell exclusively through our internet presence and select underfloor heating specialists suppliers.

It is important to us that good, accurate advice is given from people who fully understand these heating systems, in our experience the advice / guidance provided by tile shops is not of a high standard. Speak to an electrician or call our help line.

On-line prices will generally be cheaper than High Street retail due to the significantly lower overheads and  in most cases you are buying direct from a specilist supplier without paying a retailers profit.

Who makes Floorwarmers heating cables?

All Floorwarmers heating mats and cables are manufactured by Thermopads.

Thermopads are an OEM manufacturer and have specialised in the manufacture of heating cables since the 1970's.

Thermopads manufacture heating cables and mats for Floorwarmers Ambient & Warmup.