For this post I am going to look at different designs for under floor heating and what type of flooring finishes you can put on it. The one practical element of underfloor heating that all good systems require is insulation, the more you can have under it the better. I am currently having my own extension built and we have managed to put in 170mm below the screed. Essentially what this does is reflect the heat produced into the interior rather than out through the floor below. If you are designing a space that has a very limited floor depth then you will have to install an electric matt system to minimise the floor build up. Firstly I am going to explain the different types of underfloor heating systems followed by some flooring options.
The wet system / stand alone –
This type of underfloor heating can be used if you want the heat sink properties of a wet system that heats a slab and keeps it at a constant temperature but don’t have the ability to connect it to the existing radiator system. It comes with a sausage shaped boiler that runs off electricity and is efficient. To have this design of underfloor heating in your interior space your probably looking at around between 2 – 3 thousand pounds.
The wet system / integrated –
This the same as above but the system is designed to be integrated into an existing gas boiler radiator / underfloor heating system. This is what we are fitting at the moment. Your plumber will be able to advise if your existing boiler is up to the job.
Ground source heating –
I am currently the interior designer on a project that has ground source heat pumps and it is a very involved and expensive item. Because of the initial investment required it makes sense to only use this type of system if you are doing a lot of ground works and have a large space to heat, it is certainly a Grand Designs scale sort of heating system. Essentially the design of ground source heating involes laying pipes in your garden at a certain depth that is around 1 – 2 metres deep, at this depth the liquid that runs through the pipes is warmed naturally by the surrounding temperature of the ground. The liquid once warmed is pumped back into the house and around the underfloor heating system, and so on. The main running cost is the pumping of the liquid within the pipes.
The electric mat system –
The best and most cost effective way of fitting a wet system is when you are constructing a space. If you want to minimise you initial outlay and don’t have a lot of floor depth to play with then an electric mat system is a good choice. The running cost is more expensive as there is no heat sink element.
So what type of floor? –
Most flooring types can go on top of underfloor heating. The difference being that some floor finishes have insulating qualities. Here is a list of finishes in order of efficiency.
Paint – Paint is super efficient as it is very thin and can be cheap to apply. You do need to make sure the screed is of good quality and that the Tiles are the best at conducting the heat as they act as an extension of the slab.
Vinyl or rubber – Should probably be next but Dalsouple have reduced their range massively and I don’t like many of the vinyls out there…
Tiles – are great at conducting the heat as they act like an extension of the slab. There is a lot of choice out there and my personal favourites from an interior designers point of view are the timber effect and the concrete effect tiles.
Engineered Timber – is OK to use, it takes longer for the heat to transfer through, but it also takes the heat longer to leave the wood. Solid wood is not ideal as it is less stable and doesn’t cope well with the changes in temperature. It is also best to go for a hard wood engineered floor rather than a soft wood, again this is for stability reasons.
Carpet – Can be used but it is not ideal. You need to use the correct underlay that is as thermally transparent as possible. The combined tog rating of the underlay and the carpet should not be more than 1.5 – 2.2.
All of the above is based on my own personal experience, there are companies out there that will be able to give you more in depth advise and many more options. If in doubt, ask an expert!