Articles and whitepapers

Underfloor Heating and Home Automation (6/2/2006)

By Bill McConnel, Continental Underfloor Heating

Underfloor heating (UFH) is becoming an increasingly popular and common method of heating homes, thanks mostly to it being more efficient than radiator systems and therefore incurring the lower running costs - an important issue in this age of rising fuel charges.

The reason for this fuel efficiency is because UFH heats 'radiantly', meaning that the air temperature can be one or two degrees cooler than would be comfortable with a radiator system. Radiator systems rely far more on 'convected heat', which causes currents of air within a room, leading to greater heat-loss than with UFH. UFH also has the advantage of being discrete and aesthetically pleasing, since the pipe work is buried in the floor and the manifold and associated controls hidden away in a convenient cupboard.

Building an airing cupboard for the manifold and controls

Prior to the building regulations change in 2002, which now requires all floors to be insulated to reduce heat loss, UFH required additional insulation to operate effectively, and this cost more to install. For new builds however, this is no longer the case.

UFH system types

Underfloor heating falls into two main categories, namely 'electric' systems and 'warm water' systems. Generally, electric systems are chosen for installation in single-room projects, whereas warm water systems are more commonly used in whole-house installations. Water-based systems are better suited to whole-house projects because they are generally cheaper to operate in larger areas than electric systems.

Traditional warm water underfloor heating has pipework embedded in the floor screed, with insulation below to 'reflect' the heat upward. Each room has its own thermostat that is typically hard-wired back to the manifold controller. The manifold controller essentially acts as a wiring centre to link the relevant thermostats to the appropriate thermal actuator valves. When there is a demand for heat from the thermostat, the valves open to allow the heated water to flow through the pipe work.

Pipework

Superficially, it would appear that there is very little differentiation between one UFH product and another. Pipework is probably the best starting point. All UFH pipework is constructed from a plastic or plastic composite material. The two main materials used are polybutylene pipe or a polyethylene pipe, in various guises such as PE-RT or Pex. All these materials however, allow oxygen to percolate through them. This oxygen will eventually dissolve into the water, causing corrosion on the metallic parts of the system. For this reason UFH piping requires some form of oxygen barrier. This is achieved by layering the pipe with other materials, which are usually sandwiched between the two layers of the main pipe material. This oxygen barrier can either be made out of another polymer such as EVOH (Ethylene-Vinyl Alcohol Copolymer), or aluminium.

The aluminium layer has two advantages. Firstly, it provides a 100% oxygen barrier, and secondly, it also allows the pipe to be bent, and once bent, to stay in place. This is a distinct advantage when installing, since no specialist fitting systems need to be used. It is also important to ensure that all joints are fully accessible and piping is not be jointed below floor level.

Wet underfloor pipework

For warm water underfloor heating systems, the water flow temperatures are much cooler than those used for radiators. This has two significant environmental benefits. Firstly, it makes UFH ideal for use in combination with alternative heat sources such as geothermal heat pumps, and secondly, it makes maximum use of condensing boilers with low flow and return temperatures, ensuring that the boiler runs permanently in its highly-efficient condensing mode. This ultimately reduces the fuel bills and carbon emissions.

Covering the pipework of an underfloor heating system

UFH and home automation systems

Home automation systems can link all systems within a house, such as security, heating, ventilation, lighting, and audio control, to one main control point to improve comfort, convenience, and safety. UFH is suitable for linking into a home automation system. There is already a wiring centre and electrically-actuated flow control to each room. Depending on the system, all that is required is a 230-volt or 24-volt signal to be switched live to the manifold controller from the room sensors via the house control centre. This means any room can be controlled completely independently of any other area. Frequently, these systems are not hard-wired but controlled using wireless technology.

If an automated system is being installed, it is always worth checking with the home automation supplier and designer that the UFH system and home automation system are compatible, and exactly who is supplying which components. This will avoid installation problems and potential duplication of components.

One of the key benefits of installing UFH in combination with home automation is to achieve greater energy efficiencies; this can be achieved by combining the UFH and home automation with optimisation and compensation systems.

The optimised-start system

An 'optimised-start system' works by predicting what time the UFH will have to turn on to ensure that the required temperature is reached. For example, if a customer requires their UFH to be set at 20 degrees Celsius at 8:00 am, then the optimised start system will note the external temperature and internal room temperature, and using this information, will start to heat the room so that it reaches the desired temperature at the required time. Heat is not lost by keeping the system turned on when it is not needed.

Optimisation systems will also help to control the flow temperature to the manifold, to match the heat loss from the building. This again means that the system will run at even lower temperatures, providing more efficiency.

Compensation software adjusts the room temperature based on the external temperature. For example if it is a very warm day outside the software will 'compensate' by reducing the internal temperature. It is however, important that the compensation software is designed specifically for the UFH system, since the characteristics are different from those of a radiator system. The system will only start up when required, and may even become more efficient over time, as most compensation systems are self-learning.

Conclusion

As more people choose home automation systems to control lighting, security or heating, questions will arise as to whether underfloor heating can be linked in. As this article has shown, UFH is uniquely placed to compliment any home automation system, ensuring comfort as well as enhanced energy efficiency and cost savings.

By Bill McConnel is the Technical Director of Continental Underfloor Heating, UK-based provider of a comprehensive range of UFH systems.

www.continental-ufh.com