Under floor heating (also called UFH) is a favorite technique of many northern European countries for their home heating needs as it offers a wide range of advantages, the simplicity of which being not the least of them.
Types of Under Floor Heating
Basically there are two types based on the source of heat energy source, namely;
• Electrical
• Wet Method (also called piped or hydronic)
Of these the former fell in to unpopularity somewhat because of the currently prevailing high cost of electricity, though the installation itself is simple requiring less labor and modifications to the floor construction. However under certain conditions (say for example in some existing solid floors) electrical heating may be the most viable.
The latter on the other hand does not consume a lot of electricity (yes, wet system too needs a bit of electricity!) and the source of heat which is hot water may be already available from the exiting boilers of whatever type. The preferred type by the house owners however is the condensing type boiler (which when operated with gas or oil show over 95% fuel efficiency by themselves).
How do UFH systems work?
UFH systems practically convert the input energy in to radiant heat. Under floor heater cables or the hot water pipes dissipate the intrinsic heat through the screed above (and through what ever the floor covering such as the tiling, carpeting etc.) as radiant heat. This naturally does away therefore with the need for radiators, convectors etc.
Zoning
In the case of the wet system if you still want to use the existing boiler as the source of hot water, the plumbing can be breached in and a manifold (which comprises of water in and out headers, pipe connections along with isolating and regulating valves) can be inserted according to the zoning needs of the new hot water distribution. A total retrofit too may not be that different when being installed.
Sizing of zones and components
A zone is generally a single room in a house and the floor area may be 15 to 20 m2 or so.
The heat load required in this case may be in the region of 2 kw maximum.
Each zone will have its own control unit comprising of an in-line circulating pump (having a total head of about 4 m), isolating valves and a thermostatically operated mixing valve similar to that in a radiator. The thermostat itself may be under floor design or programmable wall mounted type depending on your requirement.
Approximately 150 m of 15 mm dia. pipes may be required for this zone again depending on the zone pipe lay out. There can be larger zones and the capacities will vary accordingly depending on the design demands accordingly.
What are the Wet System Components?
In general the following are necessary when you consider a Zone of up to 20m2 area;
• Hot water piping made of Poly Butylene or Cross linked Polyethylene. Bore is in general 15 mm dia.
• Manifold with valves for zone temperature regulation and isolating. The number of valves will be double the number of zones (as one for inlet and another for out let is required per zone).Other items will be a radiator key, mounting brackets, drain/air bleed valves,
• Control unit comprising of a Mixing valve, circulating pump, and programmable room thermostat (or an under floor thermostat).
• Clips, tracks and miscellaneous fixing accessories.
• Electrical power supply to the circulating zone pumps and the control cabling to room thermostats
Electrical Heating
The Heater cable can be simply laid below the screed. To prevent disturbance of the spacing a rigid mesh is used as fixing base .The preferred operating voltage may be low stepped down 24V,115V etc. But 240 V is also used. All power cabling should conform to local regulations, IEE regulations and European Norms.
Whether it is a Wet or an Electrical UFH system, the sub floor must be adequately insulated if the system is to function at higher energy efficiency. A reflector foil too may improve the energy dissipation upwards. The uniform distribution of heat contributes to the better energy conservation in the under floor heating systems.
Thanks the Techstore Team
