Underfloor Heating – Under Floor Heating

Underfloor Heating Guide

Article Summary: Under Floor Heating is undoubtedly the best and most comfortable form of heating available. This article explains what it is and how you can benefit from fitting it in your home.

Hydronic underfloor heating works by embedding a continuous water pipe in a concrete slab underneath the floor covering. Because a much greater surface area is heated, the temperature of the floor surface is much less than a conventional radiant wall heater.

These two diagrams show the main difference between a conventional system and an under floor system. As you can see, because the conventional radiator system operates at much higher temperatures, all the heat rises rapidly to the ceiling while with the low temperature under floor heating system, heat rises much slower, resulting in a much more evenly distributed heat.

Another advantage of this type of system is the running cost – they are cheaper to run due to the fact that no energy is wasted. For hydronic systems, hot water can come from many sources; water heaters, wood boilers, heat pumps, or even solar water heaters.

People still get worried that pipes buried in concrete slabs will crack and leak. While that might have been true several decades ago, the modern variety of piping is made to withstand exposure to hot and cold water and being buried in concrete.

A house to be heated by this method is first split into zones and a plan is made of the layout of the piping. Each zone can then be separately heated or turned off completely when not in use, or special thermostatic control valves can be used to automatically control room temperatures, similar to that of conventional hydronic heating systems. the pipe is laid out similar to the diagram on our right:

A concrete slab is the perfect choice to complement under floor heating. Not only can you insulate the slab itself, by using insulation under the slab and – more importantly – around the slab perimeter, but you can utilise the heat retention qualities of the slab in conjunction with under floor heating. The amount of insulation will depend entirely on what part of the country you live because the ground temperature will obviously be different around the country. A slab thickness of between 4 to 6 inches (100-150mm) is ideal for this purpose.

Electric Underfloor Heating systems have the added advantage over the hydronic variety that they can’t leak and they are incredibly thin – about 3.5mm thick! They can be zoned like hydronic systems and can be easily retrofitted to older premises. Once fitted they are practically maintenance free and are more efficient than traditional radiator syatems. Under tiled or solid stone surfaces they are not only practical but they add a special feel that only under floor heating can give. One other advantage is that no space is lost on walls where radiators would once have been.

Distribution of heat in rooms heated with under floor heating systems is opposite to normal radiant systems. At feet level, if the temperature is around 72°F (22°C) then at head height the temperature will be around 66°F (19°C). Of course the temperature can be altered to suit your own preference, but the distribution stays the same and is opposite to that of ordinary hydronic radiator systems where your feet are always colder than your head.

To sum up the benefits of under floor heating systems:

  • Better heat distribution.
  • Warmer feet than head.
  • Zero maintenance.
  • No drafts as with radiators.
  • No wasted wall space
  • Reduces dust circulation.

Which one should you choose?

Well, each has its benefits and drawbacks. It really depends what the climate is like where you live. If you live a permanently cold climate that necessitates heating being turned on for long periods of time, then I would recommend hydronic under floor heating. Part of the reason is that because the heating pipes are buried relatively deeply in the concrete slab, you are heating up a large mass of concrete before that heat dissipates into the room. There is nothing wrong with this of course, unless you need a quicker responding system, i.e., electric.

Because electric systems are just under the surface, they are much quicker to respond to demands for heat. They are also much thinner than hydronic systems, and as mentioned above can be fitted to older properties. If electric cables do ever need repairing, it is also easier to locate a fault and hence reduce any damage that might be caused repairing it.

Installation and Running Costs. Vary enormously due to the fact that hydronic systems can use so many heat sources to heat water. If you have a large number of sunshine days but still need to run your heating, then solar heating can be very cheap to run. It is also worth considering the size of the room(s) you are heating. It would be foolish to install a hydronic heating system, for example, in a small bathroom. Here an electric system would be the obvious choice.

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