WWW.HPMMAG.COM ‘Versatile, cost effective and efficient’ Heather Oliver, marketing manager of Nu-Heat Underfloor and Renewables, discusses the different factors to consider when installing warm water underfloor heating... 40 Got a story? Ring us on 01732 748041 or e-mail twood@unity-media.com DOMESTICHEATING Warm water underfloor heating (UFH) is widely specified in new properties and increasingly in retrofit projects. It can be installed by any competent plumbing and heating engineer, although the system design is best carried out by an experienced design and supply company. The first thing to decide is whether the property is suitable for UFH. Every new home will have been built with sufficient insulation to meet current Building Regulations, making it ideal for UFH. The general rule is; the more insulation there is, the lower the flow temperature of the UFH can be set and the better the system efficiency will be. Homes built within the last 20 years are also likely to have reasonable levels of insulation as well as double glazing and will be able to benefit from retrofit UFH products. That is not to say that houses more than 20 years old can’t have UFH, just that it will perform more efficiently if additional loft, floor and wall insulation and double glazing are installed. The next consideration is the heat source. In most cases a gas condensing boiler will be fitted and this is ideal as the UFH flow temperature is likely to be less than the dew point (53°C), which will allow it to work in condensing mode for more of the time. Oil and LPG boilers, or any controllable heat source, are also perfectly suitable and will perform efficiently with UFH. The combination of a ground or air-source heat pump linked to UFH is the perfect partnership – the performance of the heat pump will be improved by flow temperatures often as low as 35°C-45°C, which will allow it to deliver a high Coefficient of Performance (CoP is the ratio of heating provided against electrical energy consumed). SPECIFYING THE RIGHT FLOOR CONSTRUCTION The choice of which floor construction to use is usually decided by the system designer and the installer, sometimes with input from the homeowner. There are several considerations to take into account including: whether it is ground or first-floor, a concrete or joisted sub base construction, the amount of heat output required, the intended floor coverings and also whether it must conform to the Part E acoustic regulations for flats and apartments. There are four main UFH construction types: screed, including traditional hand-applied and liquid versions; floating floors, usually a moulded polystyrene panel with heat diffuser plates to hold the pipe between (or over) suspended timber joists; and, finally, the acoustic variants already mentioned, some of which are classed as Robust Details and others that will need pre-completion testing. Whatever the situation and specific criteria of the project you are working on, there is likely to be a UFH floor construction that will suit and if not, an experienced supplier should be able to create one for you. SCHEDULING THE UFH PIPE INSTALLATION Once the decision on floor specification has been made it will be possible to schedule the installation of the UFH accordingly. In the case of a screed floor, the UFH is held in place onto the floor insulation layer and should be installed just before the final screed is laid in order to avoid damage to the pipe (remember, pipe should be under pressure while the screed is poured). This is classed as a wet floor construction and as such the final floor coverings cannot usually be laid until the screed has dried FEBRUARY 2014 HEATING & PLUMBING MONTHLY out; as a general rule of thumb screed suppliers recommend around one day for every millimeter of screed. Obviously, a floating floor system cannot be laid until all of the floor decks are in place and it is best to install the UFH just before the final chipboard layer will be fitted, as this avoids damaging the pipe, the polystyrene panel or the metal heat diffuser plates. As it is a dry system the final floor coverings can be laid as soon as the deck is in place. Different suppliers have different solutions for suspended timber floor constructions. If fitted from below the metal heat diffuser plates are attached to the bottom of the deck above, if fitted from above they are suspended over the top of the floor joists; either way the pipe is held in close contact with the floor deck for fast heat transfer. Again, this is a dry system and the floor finishes can be fitted immediately if this fits in with the build schedule. All UFH floor constructions are relatively easy to install, so the choice is yours as to where you wish to fit into the build schedule. Wet systems have to be fitted earlier as they need time to dry out, whereas dry systems can be added later in the schedule and are often used when the customer chooses UFH as an afterthought. Whatever the floor construction chosen, the UFH pipe must be filled, flushed and pressure tested before it is covered by the deck or a screed layer. CONNECTING THE SOURCE AND CONTROL SYSTEM With the individual pipe coils connected to the manifold and pipework from the cylinder or heat source connected to the manifold, the next step is to wire up the manifold actuators to the wiring centre and then to the individual room thermostats. A good supplier will provide first fix wiring requirements for the thermostats and detailed mechanical and electrical system schematics to show the positioning of the various mechanical components in relation to each other to allow straightforward commissioning of the system. Recommended flow temperatures for each zone should be supplied as a starting point, and each can be fine-tuned for perfect comfort. Warm water UFH is straightforward to install, versatile, cost effective and an efficient method of heating a home, added to which it can be a lucrative addition to your portfolio of services. The keys to a successful installation are a good supplier and good planning, if these are in place the rest should be straightforward. enquiry number 128 Liquid screed is installed over warm water underfloor heating
HPM February 2014
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