Frequently asked questions

There are two types of underfloor heating systems - Electric systems, which is made up of electric heated matts and wet systems where water circulates around within polyethylene pipes. Both methods are installed within the floor. The heat produced from underfloor heating systems comprises 70% radiant heat and 30% convection heat. Floor heating is as close as you can get to the ideal heating curve.

Underfloor heating systems can fulfill the heating distribution requirements of any home or workplace. Where you may be renovating or adding on an extension, we offer pre-made Add-on kits purposely designed for kitchens, en-suites, conservatories and extensions. Enabling you to have the advantages of underfloor heating in new areas without changing your entire heating system.

There are many benefits of installing underfloor heating:

• Underfloor heating is the most comfortable form of heating system, unlike radiators or
  blown air heating systems, the heat is distributed evenly throughout the home or workplace.
  Due to the even heat distribution, temperatures are slightly lower than you would have with
  a conventional heating system, enabling you to reduce the actual air temperature by 1ºC to
  2ºC without compromising on comfort. This reduction in air temperature without
  compromising on comfort reduces energy consumption of between 15% and 50%
  depending on ceiling height.
• With little to no convection heating, underfloor heating reduces the movement and
  circulation of dust particles, improving comfort for allergy and asthma sufferers.
• With lower running temperatures, underfloor heating can reduce running costs and is
  complimentary to heat pumps. Overall, underfloor heating creates fewer CO2 emissions in
  warming your property, protecting the environment.
• With underfloor heating installed within the floor makeup, it offers complete freedom for
  interior design, with no need for radiators.
• Our underfloor heating systems are fully controllable with automatic thermostats for predesigned
  zones, controlling the temperature of the entire system with minimal involvement.
• Underfloor heating systems are quicker to install than traditional radiators. Our quality pipe
  is highly flexible and can bend round corners, reducing the need for joins, saving time and
  money.

We design our underfloor heating systems into zones. These are based on how the building is used and the orientation of the property to maximise solar gain. Each zone is then controlled by a room stat or sensor which monitors the room temperature, this wirelessly communicates to a thermal actuator which controls the flow of hot water (and thus the temperature) of the underfloor heating. This enables us to maximize the efficiency of the system by reducing wasted heat. Typically we would place a thermostat in living areas, smaller auxiliary rooms such as utility or down stairs toilets would run off a near by zone.

The simple answer: underfloor heating takes up to 1-2 hours to bring the room up to temperature from a pre-heated system (i.e. the heating circuit is at least 15 degrees C) or can take between 4-8 hours from a cold start (i.e. the system has been off).

The above information can vary depending on many factors. Firstly the make up of the floor. The thickness of the floor, in particular the screed and the type of screed used can all have an effect. The additional mass of thicker thermal stores (i.e. the screed) hold onto the heat, although they may take longer to heat up they will keep the room at temperature for a longer period of time. The other factor that would influence the warm up time is the temperature of the thermal fabric of the building which is influenced by the thermal efficiency of the property.

A set back function on the system will ensure that once the return temperature drops to a minimum level, a new heating cycle is initiated to maintain the temperature. Typically this is set at 15 degrees.

Many people who have installed wood floors, even with conventional heating systems have had substantial expansion and shrinkage which results in uneven warped floors. When it comes to finishing your floor with wood, is is always best to source quality products from a reliable source. The moisture content of the material should be between 6-10%, the lower the better, it is important to follow the instructions of your supplier regarding the acclimatisation or drying out of the timber before you begin installation.

Greener Heat recommends that the planks are no longer than 1.5m long and 90mm wide, this will allow for some flexibility in the material during the acclimatisation period. Other floor lengths can be successfully installed, however the moisture content and acclimatisation process can effect this.

To prevent the timber floor from absorbing additional moisture from the screed, a damp-proof membrane should be installed below the underfloor heating, and the heating system should be left running for at least one week to allow the concrete to completely dry out. These simple measures will prevent moisture being drawn up from the lower layers. If this is not done, a high damp tension will occur, condensing on the newly laid wood floor, increasing the moisture content and causing expansion.

When laying your timber floor on your screeded underfloor heating system, we recommend turning off the heating 24 hours before, using a Lekol 5500 glue which contains no water. Once laid, the under floor heating system should be left off for a further 24 hours, and then slowly brought up to temperature in increments over a week, this would allow the wood to slowly acclimatise. Further instructions from the floor supplier should always be followed.

To maximise the heat output from your underfloor heating, a good contact must be made between the screed and the finish, depending on the material the finish should not be thicker than 12-22mm and all air pockets or insulating materials should be avoided.

Suitable Materials include:

• Stone
• Concrete
• Tiles
• Bamboo Flooring
• Carpets - must not exceed 12mm
• Laminate flooring - with underlay less than 2mm
• Hardwood flooring - must not exceed 22mm and have less than 10% moisture conent

Non Suitable Materials:

• Thick cork
• Soft woods

We generally advise to use an adhesive material to fix the finish floor covering to the screeded underfloor heating, this minimises air gaps and allows the heat to transfer between the two materials. Any materials which have insulating properties are best to avoid or minimise.

There are greater benefits to be had by properties with high ceilings when underfloor heating is installed. The high temperatures from radiator systems, blast the heat for the room from a small surface area across a large volume. Much of this heat rises before heating the room. Underfloor heating works by gently heating a much larger surface area. Typically this results in improved comfort levels and gives energy savings of between 15% and 50% depending on ceiling height.

Any boiler or controlled heat source that can produce heat from 40ºC to 90ºC can be used to heat underfloor heating systems. Examples of successful combinations include, ground source heat pumps, district heating source, wood chip burners, wood burning stoves, back boilers, condensing boilers, combi or system boilers with hot water cylinder, oil or gas fired boilers, Agas and Rayburns.

When installing underfloor heating systems, every care should be taken to avoid damaging the pipe when wooden floors are being installed or while the pipes are exposed. Care should be taken to avoid drilling or cutting into the floor. We minimise the risk by providing drawings that show where pipes have been laid, however, accidents do happen and we supply a special pipe connectors to repair leaks. At the point of the leak, the pipe would have to be accessed, the damaged part cut out and a straight connector would then be fitted to repair the pipe.

The pipe we supply is a 5 layer PE-RT pipe with an oxygen diffusion barrier to prolong the life of the pipe. We offer a 50-year guarantee on the pipe, however the life expectancy of the pipe will easily surpass that and could last beyond 100 years.

Underfloor heating can be installed into any existing property, however it comes down to the time, cost, and disruption fitting such a system into your property can cause. Typically in older properties, the floor will have to be taken up to lay the pipework, this level of disruption will vary on whether it is a solid floor, or suspended wooden floor. Installing the underfloor heating pipe can also result in raising the floor level of solid floors with the inclusion of insulation, the pipe, screed and finished layer. Floor levels would be increased between 75-95mm depending on the insulation, and screed thickness.

If these factors deter you from installing underfloor heating, an alternative of wall heating is available. This has many of the advantages of under floor heating, without the disruption of installation.

There is no reason you can’t have radiators upstairs and underfloor heating downstairs. However, we would always recommend that these two heating systems are on separate zone valves and timer. Underfloor heating and radiators take different time to heat up and cool down, and thus must be separated in order for both systems to operate efficiently. It is also worth mentioning that you would need to install a magnet cleaning system. This removes any debris from the hot water that might be created by internal rusting of the radiators, this would otherwise block the under floor heating pipes.

We would always recommend that you use underfloor heating both upstairs and downstairs. The advantages of a quick install, many floor construction designs to choose from, seamless runs of pipe (so no weak points in copper joins) and lower running costs, there is no benefit to having radiators upstairs.

Screed is an important part of underfloor heating, not only does it protect the pipework and makes up the finishing floor level, it also acts as a thermal mass holding onto the heat to maintain an even room temperature.

Screed is a type of cement which is layerd above the floor insulation and below the floor finished (rather than using a suspended timber floor). The types of screed vary in cost an performance. There are self leveling screeds, semi dry (sand cement) and a variety of eco screeds made of recycled material and have higher thermal retention qualities.

The job of laying the screed is usually a job for either a specialist floor screeding firm or your plasterer. You can expect floor screed to take around 30 mins per meter square to lay - so a 100m2 floor area should take about six man-days to screed and expect to pay around £18/m2 for labour and materials. This will of course varying depending on the complexity of the project and the individual size of the rooms. Following pouring, the screed will take anything between 12hours to 2 days to set, depending on the variet, taking a further 3 weeks to completely dry out before the final floor finish can be laid. It is always advisable to pour any screed so that the work is completed by the Friday, giving you the weekend to completely set.

To ensure the screed doesn’t crack after installation, with the expansion caused by using underfloor heating, BS EN 1264 recommends that you limit the area to be screeded to 40m2, or 8m lengths in any one direction. With larger areas, these should be seperated into bays using a flexible expansion material. To further reduce the risk of cracking you can add mess or fibers into the mix.

The simple answer is yes. The amount by which underfloor heating is cheaper to run depends on many factors such as the efficiency of the building and the ceiling height. Typically, with current building regs, and average heigh ceilings, savings are between 10-20% per year. This is further improved when using a ground source heat pump, which runs more efficiently with underfloor heating than radiators. The yearly running costs of underfloor heating, with current building regulations comes in at £3-£4 per square meter. This obviously depends on the current fuel prices and your insulations levels, a comparable with radiators comes in at £3.50 - £5 per sqm. The lower running costs are the result of lower circulating running temperatures, and the thermostatic control in the room/zones which maintains room temperatures at the desire temperature while minimising waste.

There is often limited wall space in a conservatory, making underfloor heating ideal for this space. As long as the heat output from the underfloor heating is greater than the heat loss through the glazing, then a stable room temperature can be achieved.