Underfloor heating
- Will Hazlerigg
- Mar 1, 2017
- 3 min read
So Underfloor heating (UFH) is a topic that sparked my attention recently due to a friend telling me, in some distress, that soon after moving into their new home they received a giant electricity bill. The bill showed that they had used around 2,000kWh of electricity in one quarter (the average household uses 4,000kWh annually). They could not work out how so much electricity had been used. After an investigation of their new home and some analysis we identified the culprit - their underfloor heating system. They had not even realised that it was turned on, let alone such a massive drain on their energy usage. This situation affects a number of households so let me elaborate on why.
As with most energy-saving products the efficiency is very dependent on exactly what version of the product is installed. In the case of underfloor heating there are two systems to consider - ‘wet’ or ‘dry’. Whether you install a wet system (water-based UFH pipes) or dry system (electric heating elements) is completely down to your home, existing energy sources available and where the UFH will draw its energy from. Predominantly I have always promoted ‘wet' systems over ‘dry’ - electric systems are often much more expensive to run no matter how cheap the install cost are - but there are occasions that an electricity-based ‘dry’ system could work.
Let’s delve a little deeper into the technology and build of the two systems. A ‘wet’ system consists of water pipes running under your floor which are then covered with a screed (a substance that fills the gaps between piping and floorboards to aid the transfer of heat) to make them a fully integrated part of the floor itself. This method is more likely to be the primary heat-emitting system for your home, working with a boiler or heat pump to enable you to better heat your house due to the efficiency of the UFH by requiring a lower average heating temperature from your boiler Alongside a heat pump this method is really the most effective and is up there with the most energy efficient ways to heat your home. In comparison with the ‘dry’ system the install costs are the only real setback that I see, at an average of £75 per square meter compared to £20 plus per square meter for electric. This is a clear reason why the ‘wet’ option is often overlooked. Counter-weighed against these costs for the ‘wet’ system is the fact that it is intended to be the primary heat emitter for your home, removing the need for radiators and other heat sources. As you can see it is more expensive but that cost would be recuperated in savings over time due to lower energy bills, not to mention a more comfortable constant temperature in your home without having to worry about the cost.
Onto the ‘dry’ electrical system and as mentioned previously it is cheaper to install, so is perfect if you are planning to put UFH into a new bathroom to work alongside an existing heating system for example. In situations where you are installing into a smaller space (2.5 - 5m²) then it is clearly the better option due to ease of install, cost and scale. If the system is well programmed - timed to be on only when you need it and therefore off for the majority of the time - then it can be efficient. Where a ‘dry’ system is really not applicable is as the only heat emitter in the house. In this situation it would cost a fortune to run as illustrated in the example at the beginning of this article. What they are designed for is to work alongside radiators and for when it is really cold, saving your feet when going into the bathroom on a cold morning!
With the variety of renewable energy sources available the effectiveness of each product on its own can be dramatically altered when combined with others. The underfloor heating tables turn again if you have solar panels, a wind turbine or micro hydroelectric generator. If you do then a ‘dry’ underfloor system would be cheap to run, as your electricity would be renewable and therefore self-sustaining, however I would still not advise you use dry UFH as the primary heating source.
So the lesson learnt here is that every home is different and therefore all options available to you and your home should be considered carefully before making a decision. You must make sure that you are not going for a product just because it is the cheapest to install. This could end up costing you a fortune in the long run, as my friends found out.
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