Underfloor heating systems can be run using most heating fuels, which means it is an option available to most homes.
Unlike central heating with radiators which mostly heat air that then travels round your home (called convection), underfloor heating provides a mix of heat radiated from the floor. They use convection heat to creating a comfortable and constant temperature between the floor and ceiling.
Underfloor heating systems come in two types, wet and dry.
‘Wet’ underfloor heating systems
Wet systems can be run using a conventional gas, oil or solid fuel boiler. They can also be run especially efficiently by heat pumps which produce lower-temperature heat, particularly appropriate for underfloor heating systems.
In wet systems, heated water is circulated through reinforced polythene piping, usually with separate circuits for different rooms or areas. Each circuit is connected to a control unit – called a manifold – which has regulating valves and a thermostat so different rooms can be heated to different temperatures and at different times. A circuit will close when a room reaches the desired temperature and open again when it falls below.
‘Dry’ underfloor heating systems
Dry underfloor heating uses electric wires that heat up when electricity is switched on. The system will either come as ready-made mats or lose wires that need to be fitted. Dry underfloor heating should be connected to individual room thermostats so that each room or area has its own temperature.
Electric underfloor heating is often preferable for existing builds as it’s easier to install than water pipes and can also fit more awkward spaces. It’s also likely to be more responsive than wet systems so a room will warm up quicker. But, electricity is considerably more expensive as a heating fuel than gas, so it’s likely that these systems will be more expensive to run.
There are three main types of wet underfloor heating, depending on the type of floors that the building has:
|Solid floors||Solid floors are the common choice for new builds or large refurbishment projects. Here, the underfloor heating is built into concrete or screed floors, making it a permanent feature. Insulation is laid first, with the pipes then put down in a specific pattern before the concrete or screed is poured. Many types of floor finish can be laid over it, including wood, stone, tiles or vinyl (also carpet, though careful consideration is needed to ensure it won’t be affected by the heat or insulate against it).|
|Suspended floors||The heating system is inserted between the joists or battens in the suspended timber floor, with suitable insulation below. The pipes are usually laid within a tongue and groove floorboard casing that allows a range of floor coverings to be fitted on top, with the same considerations as described above.|
|Floating floors||Floating floor is the quickest type of underfloor heating to install. It can be used above an existing solid or wooden floor, making it ideal for renovation. Here the pipes are inserted into preformed heat plates that rest in grooves in the insulation. As the system is fitted on top of your floor, be aware that this can significantly raise the floor level.|
Cost of underfloor heating
Installation costs can vary hugely, depending on whether you choose a dry or water-based system, the number of rooms you want to heat, whether in the system is for a new-build home, extension or an older building, and what kind of flooring you have.
Roll-out mats for underfloor electric heating start at about £180 for 10m2 plus the costs of insulation board, floor covering and heating controls. This type of underfloor heating system is an option for a skilled DIY-er, which would help keep costs down.
The price of installing a ‘wet’ system can vary according to factors like whether the room you’re heating is on the ground floor, or how close it is to the boiler. But, it will almost certainly be more expensive than laying electric mats for a ‘dry’ system. It’s a good idea to speak to an engineer to help you decide whether the work and cost of the system will make it suitable for your home.
Underfloor heating pros and cons
The chief advantage of underfloor heating is that it feels comfortable. This is because the heat is distributed evenly around the room.
Another advantage is that your central heating can run at a lower temperature, saving you money. This is because the distribution area for the heat is much bigger than with a system with radiators.
Underfloor heating generally takes much longer to heat up and cool down than traditional radiators. This is partly due to the heat store (called thermal mass, which is how materials store and release heat) of the screed or concrete in which most underfloor systems are embedded. In addition, the water in wet underfloor systems is cooler than the water in radiators because the heat is spread over a larger surface area, so it takes longer to warm up.
For the system to provide adequate heat and be cost-effective, it is critical to ensure your property is well insulated and draught-proofed. This will minimise heat loss and reduce the heating up time.
Underfloor heating is generally suited to homes where people are in most of the day. That’s because the lag time described above means the heating is best left on a low temperature for a longer period of time. If people are only home in the morning and evening an underfloor heating system alone may not provide sufficient warmth.
If the underfloor heating is covered by surfaces such as timber or vinyl which react quicker to changes in temperature, then this may be a solution. But the running cost is likely to be higher, as you don’t have the advantage of a heat store to help retain and balance the room temperature.
Underfloor heating is expensive and disruptive to retrofit. It’s usually only a good option if you are already undertaking significant building work.
Running costs will vary considerably, depending on what fuel you are using to heat the system, what kind of floor covering is used and how well insulated the home is. Electricity will be the most expensive, but there are ways to bring the running costs down if you consider renewables.
How renewable energy works with underfloor heating
Air or ground source heat pumps are particularly effective when used with wet underfloor heating. That’s because heat pumps are designed to be left on for long periods of time and also heat water to the lower temperature that underfloor heating uses. You could even combine this with solar panels, as heat pumps still need some electricity to run.
The emergence of ever-improving battery storage options would make this more efficient. Newer solar batteries can ‘learn’ your consumption patterns and store any excess solar electricity, using it to power the pump when electricity is not being generated.
These batteries can also be set to charge from the grid at off-peak times if you have an Economy 7 or 10 tariff. This would both drastically decrease (and at certain times eliminate) the running costs of underfloor heating and greatly improve a property’s environmental impact.