How Does Underfloor Heating Work?
Underfloor heating can be either a system that pumps warm water through piping under the floor (a wet system) or electric coils placed under the floor (a dry system) that heat up when activated. Taking advantage of the basic physical principle that heat rises, warmth from under the floor is radiated into the room. Underfloor heating is the oldest form of central heating the Romans used a form of underfloor heating called hypocausts, which heated their buildings and baths. The current form of underfloor heating is common in the Nordic countries in Northern Europe, and has been gaining traction in the UK for the last several years.
Will underfloor heating save energy?
Savings will depend on how well insulated the building is, the efficiency and type of the boiler, and what kind of heating needs your system will be meeting. According to the Energy Saving Trust:
- In an existing home with average insulation, for an air to water heat pump system, an underfloor heating under insulated timber will save 20% of energy costs over a radiator system; £500 average per year for a radiator system vs £400 average per year for a heat pump underfloor system.
- In an existing home with average insulation, with a gas or oil-fired boiler, the energy savings are smaller only around £10 per year.
- In new and well-insulated homes, underfloor heating with a heat pump will save (£190 vs £230 average) over radiators.
- In a new and well-insulated homes, underfloor heating will save negligibly over a radiator system when heated by a gas or oil boiler.
How much does it cost?
A wet underfloor heating system will cost about a third more than a radiator system, on average. This includes the fact that more insulation is likely to be added below the pipework. Installing the system at the time of construction of a house will reduce the installation costs. Electric, or dry underfloor heating generally costs less to install, but is more expensive to run due to requiring electricity.
Is underfloor heating suitable for my building?
A wet underfloor heating system is best suited to buildings that are well insulated. Underfloor systems operate at a lower temperature than most radiator systems (35-45 degrees C). This makes underfloor heating ideal for heating from heat pumps. As a low temperature form of heating, underfloor heating is most effective when kept on continuously. It is slower to respond than traditional radiators, so is not suitable for intermittent heating. Some homes have underfloor heating in a main ground floor room and smaller intermittent heaters in other rooms. Commercial buildings might see more efficiency gains than homes, because of having a larger volume of continual occupancy.
What is it like to live with underfloor heating?
Underfloor heating is not very responsive, so after you turn it on, you will have to wait longer to feel warm. Its most effectively used where it can be left on continuously. Electric systems are more responsive, but are more expensive to run. Underfloor heating delivers a more consistent temperature, with heat distributed more from the bottom of the room. Whereas radiators will send warm air through the room, but less at the bottom of the room, the underfloor heating will send an even warmth, and will heat more at the bottom and top of the room than in the middle. Not having radiators gives you more space. But you will need to consider that furniture items such as cupboards and wardrobes should not sit above the heat coils, as they can be damaged. Bathrooms are harder to heat because the bath takes up a lot of floor space, but if you have a claw-foot tub this will be less of an issue.
Is underfloor heating suitable for a retrofit?
It is possible to retrofit underfloor heating. You will probably have to raise the floor (and adjust doors accordingly). Concrete floors are generally harder to retrofit, and suspended timber floors tend to be easier to retrofit. Electric systems are usually thinner and easier to install in a retrofit where there isnt space to raise the floor.
Will I need a new boiler?
For a gas powered system, its best to have a condensing boiler, which is most effective for low-temperature heating such as underfloor heating. Most new boilers are condensing. Underfloor heating can also be connected to a thermal store, and works well with heat pumps.
What type of flooring can I install with underfloor heating?
Underfloor heating is commonly installed with stone, ceramic or terracotta tile floors, but can also be installed with wood, linoleum or carpet. When installing with wood, you will need to keep in mind that wood will natural expand and contract with changes in heat and moisture more than stone or ceramic tiles will. This is commonly addressed by floating wood boards on a layer of polythene foam that allows subtle movement. Depending on the type of wood floor, it can also be a less effective heat conductor. That said, timber floors are more responsive, so can be more ideal where there are more sporadic heating needs. Carpet insulates, which is good for stopping heat loss from the floor, but bad for letting heat from underfloor heating in. But underfloor heating can work effectively with carpet. You need to know the combined tog value of the carpet and underlay, which should be a maximum of 2.5 and ideally lower.
Do I need a professional to install underfloor heating?
For a wet underfloor heating system, unless youre very handy with DIY, you will probably want a professional with experience to do the installation. You can expect to pay more for the installation than you would for new radiators. Installation should take a couple of days, depending on the floor space, but screed can take up to three weeks to dry.
Do I have to install the system with screed?
Wet underfloor heating systems are commonly installed with a layer of screed on top to create a level surface which the floor is laid onto. Suspended floors can have underfloor heating added without screed. And even without suspended floors, it is possible to install without screed (a dry installation, not to be confused with a dry, or electric, system) using screed replacement tiles, which are fixed together in order to make a level, floating floor. This might be preferable if you want to avoid bringing extra moisture into the building, and also means less wait time before you can walk on the floor.