electric UFH

In the previous article we looked at so-called ‘wet’ underfloor heating. This is where a boiler heats water, and this water dissipates its heat via a loop of piping installed under a floor.

However, there is ‘dry’ underfloor heating also. This is electric. The first advantage electric has over ‘wet’ is installation cost. Primarily it can even be installed by any competent diy-er. However, final connection and checks must be undertaken by someone competent and qualified to do so.

The diy installation cost can be as little as £250 for a 6.25m2 room. This would represent a whole-house cost for a typical 4-bed roomed home for around £2500 (plus the costs of hot water heating) and is quite a bit less than a comparable gas/radiator heating system. And to be fair to the electric UFH against a gas/radiator system, the electric UFH is going to be time and temperature controlled for this £2500, whereas the gas/radiator system would cost a lot more than that to control to the same degree!

Electric underfloor heating also scores more points on maintenance. There isn’t any! With a conventional ‘wet’ system annual servicing of the boiler will have to take place in addition to the inevitable breakdown of components of the system. With electric this is not usually a problem.

I well remember the truly awful electric underfloor heating of council properties during the 1960s. The cables seemed to become brittle and it had a high failure rate. Since it was buried within the concrete screed this was a considerable problem. Modern cables and matting systems are usually guaranteed for 10 years - one manufacturer offers a 15 year guarantee on its ‘ribbon‘ or ‘foil’ type. Consumers could expect a greater period of durability.

One disadvantage of an ordinary electric system is that a latex layer has to be applied over the top of the cable or matting before a laminated wood or tile floor is added. This is unfortunate. However, there are systems that use a ‘roll-out’ ribbon-type or foil heat emitter which allows flooring such as laminated wood to be directly applied. This is highly convenient and relatively inexpensive.

Most electric systems also utilise a sensor within the flooring to regulate heat output. This is connected to an air thermostat controller fitted to the wall about 1.5 metres up from the floor. The system should be connected to a residual current circuit breaker. This will cut the power if the system is ‘shorted’.

An electric underfloor heating system can either use cables or matting (with cable attached) or the ribbon/foil type. In floors that will be concreted over and/or tiled then a cable is usually used. This is simply laid in a continuing loop across the floor. Under ceramic tiles a mat version of the cable can be used which makes installation somewhat easier.

Under laminated flooring or even carpets then a matting system is used, or again, preferably, the ribbon/foil type. As with wet systems care should be taken with the thickness of carpets. It’s also important to check with your manufacturer that your electric system is suitable for wood or carpets - some are not. Indeed, one well-known system is ONLY suitable for tiles.

Control of the system can be by a thermostatic timer. This means that each room will be individually controlled for temperature and on/off times. This then is almost perfect heating control. If you want to make it completely perfect then a frost stat can be fitted somewhere usually cool (like the kitchen) or even outside. This will have to be connected to a pilot wire that is in touch with every air stat in the home. When activated it can override your time settings and - room temperature allowing - bring your heating on. Obviously, this is primarily a job for an electrician. But modern thermostat controllers allow a nightime level of heat to be set - this acts as a frost stat.

Whether your project is renovation or new build it is imperative that the ground beneath the system is well insulated. The minimum level should be 6mm of Palziv for ribbon type heat emitters. Use thicker (10mm) of a tile-backer board or dedicated insulation board like Depron for other types. However, realistically, the thicker the better. Depron is well-regarded.