Underﬂoor heating (UFH) is as the name suggests, special UFH pipes that are put underneath your ﬁnished ﬂoor. There are a number of ways that this can be done, which have been broken down below.
- Screed system – this is by far the most simple way to do it but is usually only practical when the room is being built, i.e. on a new build or an extension that is being built. The UFH pipes get clipped to the rigid insulation (e.g. Celotex) and screed directly over the top. The UFH pipes then heat up the screed which in effect turns the whole of the slab into on large radiator. Whilst it is easiest to do when the building/extension is being constructed you can do it retrospectively but it would involved breaking up any existing ﬂoor and removing debris, usually laying a new DPM, then putting in insulation and then putting in the pipe.
- Aluminium Spreader Plates (ASP) – This is a system used where wooden joists have been used, there is usually rigid insulation put inbetween the joists. The ASP’s have pre-grooved channels in them to take the pipe. The UFH pipe is then put into the groove. When the heating is on the heat from the pipe then transfers across the whole aluminium plate through conduction which increases the surface area of the heat distribution which leads to a fairly quick warm up time. On top of the ASP’s the ﬂoor is laid as normal. Again this method is simplest when the house/extension is being built but doesn’t mean that is can’t be done retrospectively.
- Over Floor Panels. (OFP) – This system allows us to be able to put insulated panels down on the existing ﬂoorboards and then the pipes get put into these panels. The panels act as both insulation and and spreader plates as they have aluminium moulded into them which helps distribute the heat. For retrospectively installing systems, or indeed in ﬂat where there are sound constraints between ﬂats, these are very good systems.
Pro’s and con’s of each
- Screed – Beneﬁts are that is quick and easy to install when the room/house is being built, downside being if you have a solid ﬂoor in an existing house and want to install UFH in this manner that its fairly labour intensive dusty job to break up the concrete ﬂoor and dispose of it all before the new insulation and pipes can be laid. Usually this system has a fast warm up time, especially when using a liquid/chemical screed as the cover is much thinner.
- Aluminium Spreader Plates – This system is good as it doesn’t raise the ﬂoor level at all so if you have limited headroom and you want UFH in a room constructed with joists, like most are, then this is the one. Down sides are joists centres ideally need to be 400mm and straight with each other. If retrospectively ﬁtting then all the ﬂoor boards need to be lifted, insulation bought and installed and any existing cables or pipes re-routed prior to the plates being put in. Can end up with quite a lot of materials on top of the ﬂoor as well which can reduce the warm up time of the room signiﬁcantly.
- Over Floor Panels – A simple system to install insulation and UFH combines. Its a very efﬁcient system as typically the UFH pipes are in near direct contact with the ﬂoor ﬁnish so the warm up time is greatly reduced. There is no major disruption when retrospectively installing other than the need to raise skirting boards and cut down doors and architraves. Even in new builds they are worth a serious consideration, especially when installing on ﬂoors above ground level due to the safety aspect. This system does make a retrospective installation easier however it may lead to skirting boards, architraves and doors being altered.
When installing UFH all connections are on the manifold. It could be that 1 coil pf pipe serves 1 room or there may be the need to use multiple coils of pipe depending on the size of the room. Once all the UFH heating pipes have been laid for the individual rooms, or zones, all the pipes ends are taken back to a UFH manifold, this manifold would ideally be sited in a fairly central position as this reduces the amount of pipe required. A manifold is typically made up of isolation valves, a blending valve, a circulating pump, ﬂow meters and actuator heads. Once connected all adjustments for the UFH can be made from here.
UFH is compatible with the most common forms of heating, natural gas, LPG, oil, air source and ground source heat pumps.
UFH works with all types of ﬂoor ﬁnishes, tiles, wooden and carpet. With some wooden ﬂoors it may be necessary to install a ﬂoor temperature probe as this limits the heat to prevent movement of the wood which may lead to gaps forming on joints. Carpets are also compatible however you may need to limit the tog value of the underlay and the carpet, as if the underlay and carpet is to thick the heat is prevented from coming through. If there are any questions regarding a desired ﬂoor ﬁnish it would always be best to speak to the manufacturers/ suppliers and they would be able to advise regarding compatibility with UFH.
In the ideal installation each of the rooms/zones would be controlled by its own programmable room thermostat, this gives the greatest control over the system which improves efﬁciency. This can lead lead to lots of thermostats and lots of cables being used, if using a hard wired system, which can increase costs but does lead to a better all round system. In recent times there has been a move toward using smart thermostat, such as the Nest Learning Thermostat. Whilst these are good thermostats and do things that the standard programmable thermostat can’t do due to the expense of these thermostats normally only 1 or 2 per house is installed which may lead to less control over an entire house.
A house can be installed with both UFH and radiators, a very common set up would be to have UFH down stairs with radiators up stairs. One thing to consider though is the use of the different systems, as the UFH has a longer warm up time when compared to radiators you need to program it differently to have it coming on earlier, but also as the UFH hold its heat for longer then you can also have it turning off earlier as well.