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Is ribbon underfloor heating cheap to run?
There is a lot of controversy over running costs of underfloor heating where it comes to electric and water based systems. Old school wisdom says that water underfloor heating is cheaper to run than electric underfloor heating, in some instances this may be true but it is important that we look at all the facts in a logical manor to understand how electric underfloor heating is cheaper to run in real life.
Lets look at a scenario
Room area is 20m2 insulated to part L of regulations the start temperature of the floor is 10 degrees and the desired temperature of the floor is 24 degrees giving a room temperature of 21 degrees, the external temperature is averaged out at 10.4 degrees based on October 2008.
Heat energy required to heat a standard sand and cement screed
| Screed Thickness | Calorific Value | Kwh Require |
| 100mm | 74,513 | 24.26 |
| 80mm | 60,965 | 19.85 |
| 70mm | 54,191 | 17.65 |
| 60mm | 47,417 | 15.44 |
Heat energy required to heat an eco screed
| Screed Thickness | Calorific Value | Kwh Require |
| 100mm | 46,695 | 15.21 |
| 80mm | 38,710 | 12.61 |
| 70mm | 34,718 | 11.31 |
| 60mm | 30,726 | 10.01 |
Ribbon underfloor heating energy requirement under a 10mm tile
| Tile Thickness | Calorific Value | Kwh Require |
| 10mm | 6,774 | 2.21 |
Based on the above scenario and figures the room itself only requires a heat energy of
2.12KWh to maintain the room temperature of 21 Degrees C for 8 hours.
Water underfloor heating may have a lower cost per 1KWH however a massive amount of energy is wasted in autumn and spring where you only require a small top up on your rooms heat.
With the faster response of the flat ribbon heating system you only use the energy you require when you need it the most.
The above calculations do not include the energy required to heat the fluid to circulate through the underfloor heating, the above caculations are also not showing loss in conversion and saying the boiler is 100% efficient which it will not be. The calculations are not showing the energy used to pump the fluids around so in reality the wet system will require more KWH than we have illustrated.
With the above scenario you would expect the heating overnight to cool, most heat loss will occur overnight meaning energy in the screed (water underfloor heating) could be lost. so based on 100mm screed at 16 degrees C to heat upto 24 Degrees on a daily basis the following energy is required.
| Flooring type | Calorific Value | Kwh Require |
| Wet Underfloor heating sand & cement Screed | 74,513 | 13.87 |
| Wet underfloor heating Eco Screed | 46,695 | 8.69 |
| Ribbon UFH under 10mm tile | 6,774 | 1.26 |
If a room is at 19 degrees C and you look to raise the temperature by 2 degrees is it really worth wasting energy to heat a screed (water system).
Scenario : Early september in the same construct as above except external temperature is 15 degrees the room temperature is 19 degrees with the desired temperature being 21 Degrees C.
The room requires 1.49KWH to heat the room and floor with the ribbon underfloor heating, The heat loss of the room over 8 hours will be 1.2 KWH meaning an additional 1.2KWH will be needed to maintain the temperature.
The above calculations are based on a well insulated house with a low heat loss factor, heating the screed or the floor covering will normally use the same amount of energy shown in the above calculations, however different properties will have different heat requirements for their rooms, with higher heat losses the efficiency will change but can still be more efficient than in-screed systems.
In a high heat loss property of similar build to the following :-
- Victorian built house with no cavity wall
- single glazed windows
- suspended ground floor with air bricks
The running cost of this will be quite high irrespective of the heating system, however in this case the property would lend itself more to large radiators. Addressing the insulation of the property will then make the ribbon underfloor heating the best choice.
Please Click here to see how we made an old victorian house energy efficient