Underfloor Heating

We now spend an increased amount of time indoors. This time is spent in our homes, offices, shops, schools, restaurants and other public places. In these places we rarely see radiators the architects and designers responsible for them have chosen, more often than not, to use underfloor heating. Underfloor heating is not a new concept it was first used by the Romans. They understood the benefits of invisible radiant heating. In some European countries it accounts for 70% of new heating installations. Today more and more of us are choosing to either build our own home or improve our existing homes. If the plans for your project include underfloor heating then this site is for you..

Here at eco hometec we strip away the mystery and high prices that often prevent homeowners and developers from specifying underfloor heating. At eco hometec you can find why more and more people are choosing underfloor to heat their homes and if it is suitable for yours. We provide a complete package with all components included, ready to install. All our equipment is manufactured and tested in Europe to European standards. Full certification is available. We take our business and your project seriously, which is why we offer after sales support to all of our customers. To find out more about design & CAD services please post, fax or email plans for a free quotation. Please select a link or submit your building plans here.

Typical CAD example of low carbon solution for larger properties, using Solar Panels and Air Source Heat Pumps. Providing underfloor heating, swimming pool and hot water heating.

Underfloor Heating

Design and calculations of wet Underfloor Heating

The design and calculations for a wet underfloor heating system in a solid floor should be conducted in accordance with BS EN 1264 and the details given on these pages are based upon this standard. The design of an underfloor heating system in a new build is a straightforward process consisting of 6 main steps:

Calculate heat losses and amount of heat required for each room or zone
Determine water flow temperature and pipe spacing
Determine manifold location
Calculate number of circuits required
Plan pipe layout
Calculating the capacity of an under floor heating system

Calculating the output of a radiant floor heating system correctly involves:

Setting the temperature of the water flowing through the pipes
Choosing the optimal pipe spacing in each zone, and

Determining the number of circuits necessary to heat the rooms It is necessary to obtain the following information about each of the zones to be heated:

Maximum hourly losses or thermal load
Heat output for under floor heating
Floor Finishes and Coverings
Floor surface temperatures when fitting wet underfloor heating
Peripheral areas
Type of flooring screeds or timber to be laid and its thickness
Controls
Heat sources
Manifold Position & Circuit Lengths
Underfloor Heating Technical Data

Some of these are described below.

Maximum hourly losses or thermal load of Wet Underfloor Heating

These should be calculated, just as you would for any other heating system, using preferably a proprietary software package or data taken from SAP rating our other reliable source. For an underfloor heating system the criteria is slightly different and this can result I lower heat losses than would be calculated for a radiator system. As more than 50% of the floor heat emitted is radiant transfer this heats bodies, objects and the building fabric without heating the air. This feature of under floor heating increases the rooms mean radiant temperature (MRT) which means a lower room temperature can be used without loss of comfort.

The same comfort will be experienced with a design temperature of 20°C when compared to a radiator system with a design temperature of 21°C because of the heat radiated from the walls, floors and the very fabric of the room. Consequently a 1°C reduction in normal room air temperature is used. For bathrooms, wet areas, and walk in wardrobes we recommend a design temperature of 23°C. This is to compensate for the reduced floor area, added ventilation and the fact you will often use these rooms with little or no clothing.

Air Changes

When compared to radiator and forced convection heating systems wet underfloor heating creates weaker convective currents. This in turn creates a more even temperature and pressure within the heated space. This fact enables a lower air rate change to be used.

Floor Losses

The floor is the equivalent of the radiator. When turned on, the floor will always be warmer than the room temperature. Consequently downward losses from the floor should not be included when sizing underfloor heating coils. Floor losses will only need to be included when sizing the boiler, heat source and distribution pipework. Downward losses should be limited by insulating the floor slab and perimeter edge.

High Ceilings

Because wet underfloor heating does not produce the same convective gradients as radiator heating no additions are required to compensate for high ceilings.

Addition for Intermittent Heating

Underfloor heating should be designed to operate at a constant temperature during the day with a night or unoccupied setback of approximately 3°C. This ensures the room warm up periods is reasonably short and no adjustments to the heat loss calculation are required.

Heat output for Wet Underfloor Heating

The formula for working out the floor capacity to heat the room is as follows:

•Total Room Heat Loss (W)/ Active Floor Area (m²)
So for a room with heat losses of 1257W and a heated area* of 14.5m² the heat output required is:

•1257/14.5 = 86.68 W/m²
* Heated area is that available to under floor heating. Sterile areas should not be heated e.g. under fridges, freezers, cupboards, baths and sanitary ware, and anywhere else you do not want under floor heating or where you may required to drill and fix into the floor.

Most rooms in new build properties will require a design heat flow of between 50-70 W/m². Possible exceptions where floor heat emission required can exceed 100W/m² are:

Conservatories or rooms with large glazed areas.
Bath and shower rooms where the available space for under floor heating is reduced by fixtures.
Rooms with open flued appliances the air change rate is greater affecting heat losses.
Rooms with very high ceilings due to the increased wall heat loss.

Floor surface temperature

BS EN 1264 floor heating and floor surface temperature. Floor surface temperature is critical to comfort, as well as to heat output. BS EN 1264 gives guidelines on the maximum values for floor temperatures.

Please browse our website for more information about eco hometec and our range of wet underfloor heating, Underfloor Heating Barrier Pipe, Underfloor Heating Manifolds, Underfloor Heating Controls & Underfloor Heating Kits then click here to submit your plans or contact us on Freephone 0800 8620278 to speak to one of our team or e-mail us on sales@eco-hometec.co.uk.