What is Underfloor Heating?
Underfloor heating dates back to the Romans. Initially only the rich could afford this luxury, then it became increasingly common to find it in public buildings and villas, particularly in the colder regions of the Roman Empire. The Roman system was based on hypocausts, comprising ducts that underlay the floor (itself built on raised brick piles) and flues that were built into walls. Hot air or steam from fires circulated up through this system, warming the floor and walls, with heat passing into the rooms.
The hypocaust was recently voted the most important heating invention ever by the British HVAC industry.
There are two types of Underfloor Heating systems available on the market.
1) Hot Water Systems
2) Electric Systems
Hot Water systems use the principle of circulating warm water through pipes laid into a solid screeded floor.
Electric floor heating systems have very low installation cost for smaller spaces (1-5 rooms) because they are easy to install and have a very low start-up cost (An electric thermostat is all that is required.)
Another advantage of electric underfloor heating over a warm-water system is the floor build up/height. Floor build up can be as little as 1mm. The electric cables are usually installed onto an insulation board or directly onto the subfloor or padding (under carpet or laminate); then the floor covering is placed directly over the heating system or thinset.
Electric underfloor heating also benefits from faster installation times, with a typical installation only taking half day to a day depending on size to install. Also warm up times are generally a lot quicker than "wet" systems because the cables are installed directly below the finished flooring making it a direct acting heat source rather than a storage heater.
Electric system used to be supplied as one long continuous length of cable with the consumer having to weave the cable up and down the floor at a pre-determined spacing and making a return loop to complete the circuit. The main problem with this was that the installation was time consuming, and also the risk of hot and cold spots due to uneven cable spacing; the closer together the cable the more heat was given off, and visa versa. With today's technology most modern cables have a built in return, meaning that you only have one end to connect instead of having to bring the end of the cable back to the start to make a full circuit. These are excellent and make the installation a lot easier. With the introduction of the built in return came the "cable mat." These have revolutionised the electric underfloor heating market due to the simplicity of the installation. Cable mats have taken the hard work out of the installation by having the heating cable already pre-spaced on to a nylon mesh. All you have to do is simply start at your thermostat location and roll it out over the floor until it's all used up. These save time and offer less risk of having hot and cold spots.
One technique is to lay the heating cable directly onto an insulated concrete floor and then apply tile on top of it. Where time-of-use electricity metering is available, this type of system can be turned on at night when electricity rates are low, and then allowed to warm the house during the day by relying on the heat energy held within the thermal mass of the concrete.
Sometimes, in order to mimimize floor buildup, a screen or carbon film heating element is used. These systems are generally used under laminate or similar types of flooring.
In comparison to combustion/hydronic systems, electric systems can be more efficient, if only the efficiency of the equipment in the building is considered. The efficiency of generating electricity from fossil fuels is low, so overall system efficiency is significantly lower than combustion/hydronic systems. Electric systems have the advantage of needing no maintenance and can more easily be controlled to run when and where they are needed.
