underfloor heating efficiency

[potty]

Can anyone please offer advise on the cost-effectiveness of underfloor heating systems ?. We and several people we know are having conservatories fitted at present, and the others are unanimously opting for electric underfloor heating - I suspect because of the comparitively low initial cost (so I understand) when compared with rads (especially the designer sort) for a large-ish space. However, I remain sceptical on the grounds that a modest rad for our space would be around 5000 BTU (1.5 Kilowatt-hours) and that the heat transfer efficiency of an underfloor system must surely be lower - because of the fact that most flooring materials (laminate/wood) offer a layer of natural insulation. On-top of that, my estimation would be based on a normal room (brick/stone-built house) not glass/polycarb. Given our idea was to use our new conservatory as a living area throught the year, my hair turns grey at the prospect of seeing the cost of this on our electricity bill.

I appreciate that underfloor systems provide a more even room temperature than rads
, and a water-based system will probably be less expensive to run than electric, but is it that people are prepared to pay the extra running costs over a radiator-based system purely for cosmetic reasons, or are they just victims of a new fad ?.

Help, I need to make a decision in the next couple of weeks !!

mod

moved as posted in wrong forum

 

[Bahco]

Underfloor heating I have been told is 25 % more efficient than having a radiator due to their lower operating temperatures.
I think it would be ideal in a conservatory as they are notoriously cold in the winter.
Have it fitted and post back with your findings.

 

[potty]

Would this not introduce a thermal lag possibly taking hours for the room to get up to the desired ambient temperature ? Was this system not designed just to just take the chill off ceramic tile floors ?

I wonder why my question was moved to Electrics from plumbing ? I would have thought plumbers were more familiar with thermodynamics than electricians ?

 

[Bahco]

The heat is being emitted from a large area and wouldn't take long to get the room at a comfortable temperature.
Remember the heat will be continually rising.
I do not profess to know much but the laws of physics will prevail.

I am referring to water underfloor heating by the way and not electric, which I believe do just heat the floor tiles and keep the pets sleeping happily.
See what the sparkies think as this has been moved to their forum

 

[Big_Spark]

In my experience underfloor heating is efficient is small controllable areas where heat loss is not a major contributing factor. I think you would need to look at each case individually.

I have seen hybrid systems where copper pipes are installed inside polypipe and laid in a pattern like a large element in the floor. These copper pipes then connect onto the normal central heating system via their own valves, with the primary valve being a motorised unit controlled by a Room Stat in the conservatory.

This system is efficient and gets over the ugly Radiator problems. All bends in the copper pipe need to be created with a pipe bender to ensure all joints are kept to the absolute minimum.

I would advocate getting expert advice before installing this type of system though as I am not sure if this is a DIY job due to the lack of readily available literature and advice on the system.

 

[mapj1]

If the aim is to heat the conservatory to the same temperature with either system, then the number of (kilo) watts to do this is the same regardless of where it comes from, if the losses are the same. HOwever, as part of an underfloor system you normally lay polystyrene in the floor slab before pouring the cement, so the losses are not equal unless you do that for radiators or buried pipes too. However, kilowatt per litre of oil or cubic foot of gas, you do better to burn it at your place, not at the power station, as at the power station they keep half the heat, and have to make a profit selling you the other half. True the electric element converts 100% of the electrical wattage into heat, but the power station only converted half the heat of the fuel to electricity. If your gas or oil boiler is more than 50% efficient, you will do better to use it in preference to electric elements. BUT you must build the conservatory floor with the same insulation, for the comparison to be fair, so its almost as expensive as the electric heating to build in. Personally I'd consider a floor with insulating slabs, with a meander of polypropylene pipe (the stuff that is good for heating systems cast into the cement scree.) YOu can buy this as a really expensive kit, see screwfix 35309 but I see no reason not to make one up from parts. See screwfix 94273 for the underfloor pipe I'm waffling about.

 

[Big_Spark]

The best sort of floor to keep heat in and prevent heat penetration is wood. There is nothing better that a good quality wooden floor instead of concrete or stone.

 

[mapj1]

OK, I was assuming a solid floor, for ease of construction. If if you build a wooden floor, you might still like to insulate it as per document L's recommendations, although if the conservatory connects to the house only by an exterior grade door, you are not obliged to follow the regs as you would be for house construction.. Hwever, I agree that in the traditional conservatory, the solid floor is a major loss of heat (second only to the roof and windows !)