Underfloor heating is widely used in cooler parts of Europe, and is becoming an increasingly popular installation in the UK. As the name suggests, it is a heating system that is installed under the floor. It provides invisible warmth that can completely eliminate the need for radiators, giving you more room in your home and more freedom with your interiors. It is a low maintenance, omnipresent part of your surroundings.
Radiator central heating systems primarily generate convection currents of hot air that rise to the ceiling, making the ceiling one of the warmest places. Underfloor heating creates a 50/50 mix of radiated and convection heat which is argued to provide a more comfortable temperature between floor and ceiling. It aims to create uniform heat dissemination so that there are no particularly hot or cold spots, and particularly it creates a comfortably warm floor on bare feet.
Underfloor heating is usually installed at the time of building as fully insulated flooring requires some large disturbance to the room or rooms.
How does underfloor heating work?
Warm water from the boiler is circulated along continuous lengths of reinforced polyethylene piping based on either Pex or Santoprene systems. Each room has its own pipe circuit that is connected to a manifold with water regulating valves, and each room can be controlled by an individual thermostat.
When the room reaches the pre-set temperature, the thermostat sends a signal to a valve on the manifold to close that room's circuit. The manifolds distribute water to the pipes at a temperature between 35-60°C that heats the floor to around 18-29°C.
Underfloor heat can be fuelled by almost any source. Usually the fuel used is oil, gas or solid fuel from a conventional boiler. Condensing boilers are the best choice to be paired with this kind of heating as they work well as the lower temperatures required. Alternatively, its low temperature operation means that underfloor systems can also be powered by solar panels, an Aga cooker, a heat pump, or a heat recovery system. These can provide additional savings on your fuel costs when used in any combination to supplement the boiler output.
Types of underfloor heating
There are three main designs in the installation of underfloor systems:
Solid floorOften the choice for new build homes, it is a permanent fixture that is built into concrete or screeded floors. In this structure, insulation is embedded in the floor as part of Building Regulations. The pipe is then laid in and set in the screed. Wood, stone, tiles, vinyl and carpet can be used in this application.
Suspended floorThe heating system is inserted between the joists or the battens in a suspended floor, either by accessing from above or below. The casing consists of a tongue and groove floor board which can in turn be covered by any kind of flooring.
Floating floorThe pipes can be installed in floating floors above an existing solid or wood floor. The pipe is pressed into a preformed heat emitter plate which rests in grooves in the insulation panel of the floating floor. Again, tongue and groove boards are laid atop ready for any kind of flooring to be fitted.
What costs are involved?
Installation companies argue that underfloor heating is no more expensive than a comparable radiator system. It is also compared to the price if a good quality carpet, with a ballpark figure of £20 per square metre for supply and installation as one estimate. The overall figure naturally depends on many other factors, and it is also held by some that underfloor heating is overall more expensive than radiator system installation.
Where to install it?
Underfloor heating can still be installed under existing flooring, depending on the floor's construction.
Wood and wood laminates: With set levels on existing timber floors, the pipes are laid between joists and not on top. This requires shelves to be installed created between the joists.Underfloor heating installers maintain that wooden flooring is an ideal material because it helps to maintain an even temperature. However, wood is also a good insulator and so may not be the optimum choice.
Advantages of Underfloor Heating
Carpet: While underfloor systems can be used with any kind of flooring, carpet is quite insulating. It is recommended that the combined tog rating for carpet and underlay should not exceed 1.5.
Once fully installed underfloor heating systems are almost maintenance free; with modern developments experiencing few problems. Quality systems are said to last successfully 25 years or more as the metal elements of brass and stainless steel do not corrode or attract scale.
The radiant system is very thin and so does not affect the floor levels. Without radiators, you will have much more wall space and freedom to decorate and re-arrange your room as you like, especially as underfloor system can be suited to almost any type of flooring.
Some installers hold that underfloor systems utilise a flow temperature of up to 60°C, and when combined with condensing boilers can achieve an energy efficiency of up to 98%, also making it cheaper to run than a radiator system. Radiators rely mostly on convection currents, whereas underfloor provides an even spread of radiated heat. In new builds, the heating system combined with the insulation will prevent heat losses that will mean comfortable warmth and lower heating bills for you.
Unlike noisy radiators and their pipes which can gurgle and creak when turned on or off; underfloor heating is a silent system that you will hardly notice when it is on. You will barely notice its presence at all as there will be no hot radiators to avoid touching or putting objects too close to.
Your home will also feel the benefits as it does not dry out the air like radiators do. Antique furniture will not suffer drying out, and neither will your skin. Moreover, the strong convection currents from radiators send dust particles around the room, which can irritate allergies and asthma. Underfloor heating has a balance of convection and radiation that creates less disturbance.
Disadvantages of Underfloor Heating
While underfloor heating is greatly beneficial in terms of space and could indeed be the way forward in energy efficient heating, it is important to look at the issues that are not always covered in the information provided by installation companies.
Full installation on an existing building requires large-scale disruption. For a permanent fixture with proper insulation the floors require a complete rebuild. You must be prepared for this chaos and its associated costs. There are DIY mats with the heating pipes attached, but these are not as effective. A fully installed system will be more expensive than a standard radiator system, and can involve additional complicated and costly controls.
For underfloor heating to be a worthwhile installation in terms of both heating bills and energy efficiency, you absolutely must have proper insulation. Underfloor systems take a while to heat up and to cool down; it can be around 24 hours; so it is not for occasional use. It does not therefore respond quickly to rapid temperature changes, so unless your home is well insulated you will have to wait for it to achieve optimum warmth. With fully insulated floors the underfloor system will have an easier job to do, and may not have to come on very often as the insulation will be keeping your home cosy.
Moreover, without proper insulation, you may find that underfloor heating is inadequate as a sole heat source. Radiators can achieve a heat of 65°C to 80°C, while underfloor heating in a solid floor reaches just 29°C, 27°C for a timber floor. As this surface temperature is relatively low, the maximum heat dissipated from a solid floor is 100 watts per square metre, equalling 70 watts per square metre from a timber floor. Consequently, if the house or room is not well insulated this will not create much warmth. It is necessary to purchase a good quality, fully installed system if you want to achieve the maximum benefits offered by underfloor heating.
With a fully installed permanent system it must achieve Building Regulations required for insulation. Without this stipulated flooring insulation, heat will be lost through the floor resulting in high bills and energy losses.
Be aware also that as underfloor heating is still quite uncommon in the UK, and as such any tradesmen who carry out additional works may inadvertently damage the system. Check with them first and ask them to tread carefully if unsure.
In an old central heating system, the boiler will have circulated the water at around 65°C to 80°C. If underfloor heating is installed it will need to be mixed with some cooler water from the return pipe into the hotter flow. The mixing is the job of the manifold which is quite a large part of the flooring equipment. It is best installed in the cellar, garage, or its own cupboard; so underfloor heating is not without its space-consuming capabilities. Compared to radiators however, the small sacrifice can surely be made.