Whilst sitting in my house with cold feet the other evening, contemplating turning the heating on, it occurred to me to write an article on underfloor heating. While perhaps it may not be comparable with installing a renewable energy system to your property, underfloor heating can still save on heating bills and carbon emissions. In this article I want to look at how underfloor heating works, what it may cost and how significant the savings may be. There are many companies out there, all selling different types of systems, and all making various claims, so I shall attempt to come up with some general ballpark figures as a guide.
How it works
There are two main types of underfloor heating: water-based systems and electrical systems. The water based systems work by circulating warm water around the pipes under the floor, a bit like a radiator in principle, but not as hot. The water is heated by the boiler and then pumped around pipes under the floor. Electrical systems simply heat an element to create the heat. Even though they run off different power sources, both types of system do the same thing; the heat generated comes up through the floor, essentially turning the whole floor into a low heat radiator, except one which radiates straight upwards. The idea is that the heat is much more evenly distributed around the room producing a more comfortable environment.
There are different ways of fitting an underfloor system. The easiest (but most expensive) is to get the whole thing done by professionals. These guys will measure up and then fit your system for you. Next come the DIY jobs. These range from mat systems, where the insulation and wires etc. all come as one mat that may be unrolled or fitted together to the appropriate size. Finally there are lose wire installations where you fit all of the components yourself. This is one for the more accomplished DIYer. Now I know this may sound obvious, but do make sure you’re competent enough to tackle the job if you go down the DIY route, especially with water systems. You don’t want to lay a floor one week, only to have to pull it all up again the next because you haven’t fitted the system properly. However, saying this, it would appear that many of the DIY kits are suitable for fitting by your everyday DIYer – such as myself
The systems come in different sizes as defined by their heat output; which is usually expressed as W/m2 (watts per square metre); the higher the value, the higher the heat output.
To maximise the amount heat going up through the floor and minimise the heat lost through the bottom, it is usual to fit an insulating material under the pipes/wires. Again the insulation comes in different sizes, defined by the thickness or sometimes by a U-Value. Generally speaking, the thicker the insulation or the lower the U-Value, the lower the heat loss. How much insulation will you fit will normally be governed by how high you can allow the floor to be raised.
Underfloor heating is very well suited to tiled, laminated and wooden floors that rest on a concrete/screed bed. Suspended floors, such as wooden floorboards in older houses, do not lend themselves so well to an underfloor system. The reason being that to fit the pipes/wires/mats would require batons to be fixed to each of the joists allowing them to make contact with underside of the floorboards. This is possible of course, but would either add to the labour costs for a professional installation or add to the time and effort for a DIY job. Fitting to a suspended floor will usually require an additional purchase of aluminium plates to distribute the heat properly.
Advantages of an underfloor heating system
Savings - In regards to the context of this article, the main advantage of using an underfloor system is that you will save money and carbon. The general consensus is that you can save about 15% when compared to gas-fired central heating (radiators). The exact amounts of money and carbon that are saved will obviously depend on the size of your property, but if you consider that space heating accounts for about 60% of total domestic energy use, then 15% off that is not to be sniffed at.
When it comes to installing underfloor heating as part of an eco-home then the best combination would be an electric system powered by a wind turbine. It course it is possible to power it from other sources, but the reason I recommend pairing it with wind is because you’ll achieve the right synchronisation. By that, I mean the highest demand for heating is in the winter, in the dark and when the wind picks up, which is also when a wind turbine operates best (funnily enough). If you are powering underfloor heating via solar energy – be it a hot water or a photovoltaic system – you are not running the heating when the solar power is performing its best, i.e. in the summer. It is also possible to use ground source and air source heat pumps, but both of these require quite a lot of energy to run them.
Comfort – I would argue that the next best reason to look at underfloor heating is to increase your levels of comfort. Because of the design, heat comes up from the floor and rises gently upward, ideally reaching optimum heat at around head height, which also has the added bonus of not heating that unused upper part of the room. Radiators, on the other hand, heat one or two sides of the room and send a vast majority of their heat up to the ceiling while missing out those proverbial cold toes. This also means that the person closest to the radiator is nice and toasty, while the person furthest away is colder. As well as eliminating hot and cold spots and the old problem of hot heads-cold feet, the heat will also radiate upwards into sofas, chairs and rugs too. Lovely.
Health – Underfloor heating will avoid the ‘chimney effect’ where the radiator acts as a dust trap, which then creates draughts consequently moving the dust and other irritants around the room. This is said to be especially beneficial to asthma sufferers. It is also claimed that it will dramatically reduce the numbers of dust mites because the moisture content of the room is too low for them, a benefit again to sufferers of asthma and other breathing difficulties.
Design – There will be no unsightly radiators to look at and the wall space they could normally occupy will be free for other purposes, such as bookcases, drink cabinets, cupboards or more drinks cabinets. Additionally, a huge proportion of radiators are situated close to windows to minimise further loss of wall space. I have heard it mentioned (by an estate agent) that they are put there to warm up the cold air coming in through the window – this is not right. Warm air always flows from hot to cold, meaning that a proportion of the heat created by the radiator flows straight out of the window. Of course double-glazing, draught proofing and radiator shelves can all go some way to alleviating this, but they won’t ever stop this problem completely.
The costs
If fitting at the same time as the floor and heating system is installed, for example in a new-build, then the price is very similar, if not cheaper, than radiators. If retro fitting then the costs of raising and replacing the floors must be considered as well as the removal of any old heating systems.
I have looked at some of the prices for underfloor heating and come up with some very rough averages – you will of course need to ask a supplier for a quote tailored to your own needs. I have based these figures on a room of 20 square metres.
For a system of 150 W/m2 expect to pay around £400 – £600. This is for a kit that will come with all the basic components you will require.
Insulation will depend on the type and the thickness you go for, but as a rough guide expect to pay between a couple of hundred, to several hundreds pounds.
Before looking at which system will suit you best, make a plan of the rooms to be heated, noting if there are any odd shapes that need to be accounted for, because on some systems the cables cannot be cut. You will need enough cable/pipe to cover 90% of the room in question and don’t forget the extras, such as thermostats and fitting clips. Have a good look at the energy consumption/outputs of the different systems available, because they can vary.
In summary then…
As so often is the case when I write these articles, I have gone and sold myself on the product and I can almost feel the heat swirling around my toes as I write this. The reality is that I don’t need to replace my radiators yet and will have to live with them for a little while longer. But that’s no reason for you to. If you are considering changing the floors in your property or simply upgrading the heating system (or both) then do consider an underfloor installation. Not only will it save you money and reduce your carbon footprint, but it will also bring health benefits, improve the design of the place, give you more room and let you relax in a warm and cosy environment – nice. Ok, that’s it. I’m off to light a fire.
