# replace storage heater with underfloor heating



## SPUDZ (12 Mar 2006)

I have storage heaters in my house. However the one in the kitchen has completely blown and needs replacement at a cost of 400euro!!
I am going to tile the entire floor and was considering putting electric underfloor heating. Estimated cost for the room is 800euro, expensive I know but would it be a better option in the long term for heating the room??What i want to know is, will the underfloor heating be sufficient to heat the whole room as the only source of heating, so I can get rid of the storage heater altogether.The room is approx 17sq m. Anyone have any experience of this??Thanks for your replies / suggestions


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## Sue Ellen (12 Mar 2006)

Hi Spudz,

You should have a read of the many previous threads on Underfloor heating and hopefully you should get some help there.

As to the tiles and underfloor heating don't forget that if something goes wrong with the heating it might well be necessary to pull up the tiles


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## z102 (13 Mar 2006)

El. heating of the floor is the most expensive form of heating.


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## owenm (13 Mar 2006)

I agree, friends of mine rented an apartment in london which had electric underfloor heating in one room, they loved it until the first electric bill came after which it was never switched on again.....ever


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## extopia (13 Mar 2006)

However, if you're replacing the storage heaters you could always install UFH in conjuction with an efficient gas boiler (availability of gas allowing) or even a heat pump.


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## z102 (13 Mar 2006)

The problem with retrofitting UFH is the initial financial burden. Either one chooses the method of using electrical UFH with tremendous running costs or the warm water filled coils under the floor with much lower running costs. Both methods demand a good insulation under the coils, min. is 10cm ( better more), and would result in a lower room height/ceiling level.The difference in floorheight for the two is only the difference between  the heat emittors, the electric coil or the water filled coil. That would be 2 centimeters.  For renting out a "habitable" flat/home the min. room height is 2.45 meters. Some say it's only 2.4 meters, but anyhow: the min. height with the average room would not be reached when retrofitting UFH. Also the height of the doors would be lowered accordingly after installing UFH, this could be a breach of safety regulations.The advice  to pull in the head when entering a room (the men of the firebrigade and the ambulance are of a somewhat stronger figure then the landlord might be ) in an emergency case, propably in total darkness and chaos, might be easily overheard.
So that means raising the floor for insulation and installing the UFH plus ripping out door frames and replacing them and raising the ceiling and maybe exchanging the windows. The windows used for the air exchange calculation have a  requirement of a min.height, otherwise they are not considered as fit for ventilation, i.e. a catflap is no ventilation by the meaning of the technical guidance documents of the building regulations.
So a lot of extra work -at least in the planning stage- is involved when changing the average home to UFH.
It might be wiser to install the standard radiators supplied by a modulating boiler.
Building homes with a higher room height from the beginning is a way of investing money for the future. The Dutch have changed their building regulations jears ago accordingly.


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## extopia (13 Mar 2006)

Yes, good points heinbloed. I would only do this kind of upgrade in the context  of a big renovation project (i.e. the floors are up already). In our case we excavated down to install the UFH and retain original floor and ceiling levels.

I think you're right - the OP should consider radiators with a good boiler (what's a modulating boiler by the way - a condensing boiler?)


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## z102 (14 Mar 2006)

One can compare a modulating boiler versus a non modulating boiler like a fuse box with a light switch: When coming home in the dark one switches on the light in the hall with the aid of one switch. This will turn on one bulb or two, depending on how many are in the light of course.
But one could as well, instead of using individual switches for the lights, switch on all lights in the entire house at once with the aid of the main fuse. But then all the lights turned on would be a waste of money, one can't be in all rooms at the same time enyoying the bright lamps.
Or compare a modulating boiler with a light dimmer: It can be set to produce an output of light that is wanted, within it's limits of course.
So a modulating boiler produces as much heat as is consumed by the radiators, as much heat as the heating system looses/gives off to the rooms. 
Turn on one radiator of 2kWh output and the modulating boiler will produce 2kWh of heat, turn on another of maybe 1 kWh output and the modulating boiler will produce 3kWh of heat. This process of modulating the output of the boiler accordingly to demand happens fully automatical, the boiler "knows" what is wanted.
Versus a non mudulating boiler (which would run on full power and switches off when exagerating the output) a modulating boiler would have long running cycles since it knows when to stop before it's getting too hot (smiley).
And using a condensing boiler is of course much cheaper then a non condensing boiler. But both-the condensing and the non condensing boilers- are build nowadays with a modulating effect. 
The worst condenser (energy rating!) can be 10 % cheaper in running costs
then the best non condensing boiler, depending on the heat demand to be compared with. Esp. if fitted with a modulating mechanism.
So for a small house/flat, one where the heat demand can be very low, just one room or so, the choice should be a modulating boiler, and even better a modulating condensing boiler.
If the smalest room to be heated has an energy demand of 2kWh the modulating rage should start at 2kWh. And when the max. heat demand for the entire complex is 30kWh the modulating range for the boiler should be 
2-30kWh.
The savings are achieved by avoiding multiple starts, imagine driving along a road and pushing down the gas pedal to get to full speed and then switch off the engine untill the car stands. Then you turn the key and push down the gas pedal again and when reaching full speed you turn off the engine again. And so on. It will get you from A to B but not very economical.


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## UpTheBanner (15 Mar 2006)

Hi,

you could check the costs of running underfloor heating on the night meter. Thus it is recharged at night and emits the heat during the day. This may not be suitable for all types of underfloor heating i.e. mesh versus a cable.

Search for a company called de-vi heat who supply both types.


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## Jack The Lad (15 Mar 2006)

I have UFH in my house. It's hot water from a boiler rather than electricity. I think it's a little more expensive, but not much. It's hard to quantify as it's impossible to compare one house with another.

I can tell you these things for sure, though...

If it's not installed properly it's a disaster... don't cut corners, particularly with floor insulation.

It's not as easily controlled as rads. ie it takes a couple of hours to heat a floor from scratch. I found it was best just to leave heating on all the time - 24/7. It doesn't cost any more as the floor is not being heated from start to finish twice a day... just maintaining heat.

It is a lovely type of heat. Very comfy as the heat radiates upward.


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## z102 (15 Mar 2006)

To UpTheBanner:
How thick a floor has to be to give enough heat off until evening before it goes into charging? If a floor is uploaded untill 6.00 o'clock in the morning and releases heat all day long and then the cold night starts at about darkness (during winter as early as 16 o'clock) - that would mean a storage capacity of about half a meter of concrete. And if giving off the heat uncontrolled during the day: wouldn't it be very hot in the morning?
Have you tried to use the thermal storage capacity of your house in such a way ? Heating it up during the night and having it comfortable during the day untill 23.00 o'clock ? Its either to hot in the morning (causing waste of energy because of the then required ventilation) and boiling the feet and  too cold at 23.00 o'clock . A floor surface temperatur of around 25 degrees should not be exceeded for health reasons. 
I have UFH myself, so I know what the issue is about. Keeping the floor warm during the 24 hours of the day is the best way to have it comfortable, a night reducing is allowed, but no total switch off. As Jack The Lad already says above.
I can't imagine this Devi heat storage system working economically or ecologically or comfortable. And nightsafer electricity might be soon a thing of the past. Why should other electricity users subsidy the night safers with their day rate payments ? The market is opening, even though the ESB is trying to slow the process.
Heating sytems should be designed for a lifetime, and putting a bet on cheap electricity-who would do that? Read the other issues about electric heating here on AAM , people are cursing about storage heating controll and running costs.

Isn't it basical physical knowledge that a material gives off heat as long as it takes to incorporate it? 8 hours night charging versus 16 hours day release doesn't ad up. And ventilation losses have to be included as well ! Plus radiation losses since a hot body gives energy faster off then a cold body - at morning the heat release would be very high and in the evening very low.Giving a comfortable temperature from 12.00-17.00 o'clock. That might be o.k. for the tourist office but not for our homes.


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## UpTheBanner (17 Mar 2006)

Hi heinbloed,

I'm not a technical expert on the workings of our underfloor heating but our settings are as follows:

Recharge set to start at 0200 and finish as 0600 and the setting on the devi monitor is 6. The floor is warm, not hot, when we get up at 0730-0800. It gets gradually cooler during the day and by about 2300 its very lukewarm. Our last electricity bill for the night-rate was 25 euro which IMHO is reasonable for 2 months.

If I have time I'll measure the floor temp at 0800 and 2300.

The advantages for us include a warm floor to walk on in the morning in bare-feet but more importantly compared to our neighbours house with the same room dimensions (34 feet x 14 feet) a warm room.


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## extopia (18 Mar 2006)

That sounds like outstanding performance to me, and an impossibly low cost! Are you sure it's not on during the day as well?


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## UpTheBanner (18 Mar 2006)

Defo not on during the day as we had to pay for an additional line from the floor to the night meter when the house was being built.


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## extopia (18 Mar 2006)

What kind of boiler do you have?

25 euro (assuming before VAT?) at night rate of 5.42c per unit is about 461 units used over the two months - or 7.69 units per day. You have heat on for four hours a day so that's only 1.92 kilowatts per hour.

Does that match the stated power consumption of your boiler or heat pump?


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## extopia (18 Mar 2006)

Well 25 euro (ex VAT?) at night rate of 5.42 cents over two months suggests your heating system is rated at 1.92kW. Is that correct? Seems pretty good to me if so. How large is the house?


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## UpTheBanner (18 Mar 2006)

The house is about 3000 sq ft but downstairs we just have the UFH in the kitchen/dining room which is effectively 1 large room (34'x14'). 

25 euro before VAT.

We re-charge for 4 hrs per day. I'm not technical so you'd be better off asking de-vi about the kW, I can dig up their contact details if you wish.

We have an oil burning boiler but we do not have the rads on in the kitchen/dining room.

We also have the mesh UFH in our en-suite but it never worked as the workmen damaged it and we only found out after the floor-tiles went on. The mesh would have been on the normal day rate but we've obviously never had a chance to compare day versus night charges.


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## z102 (19 Mar 2006)

When I read the part "€ 25.- per bill", assuming for two month, I thought:YES! There are low energy houses besides mine! And they work!
But then I read a bit further: Only for the kitchen/dining room and an aditional boiler has to be fired as well. Are there any other heat sources in kitchen/dining room except for the usual cooker,toaster etc.?
And how many m2 are supplied by the electric UFH ?
I'm using about about 52.5kwh/m2 per year for room heating only, very roughly, for every room in the house. So 52.5 devided by 12 and multiplied with 2 (to compare my annual bill with the average 2 monthly bill of UpTheBanner ) = 8.75 kwh/m2/2month.Compared with 469.09 kwh/2month/xm2 (using extopia's numbers).So the question is how many m2 are supplied by the UFH, how big is the kitchen/dining room? And how warm is it when needed in the winter, during the day? If the heated area is larger then 53.6m2 then UpTheBanner's home (kitchen/dining room) is the most energy conserving here on AAM, not for primary energy but for metered consumption. I thought my house is heated for -well- cheap....
About the damaged cable in the ensuite: an electrician can find out by non invasive measuring where the exact location of the damage is. A low current would be aplied to the cable and an electric field meter can be used to follow it. At the point where the field signal stops the interruption would be.This process doesn't demand much labour input (non invasive) and since the entire area is propably small it mightn't take more then half an hour. So it might need only the lifting and replacing of a single floor tile to get access to the repair point.


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## UpTheBanner (19 Mar 2006)

The kitchen is 44.22 sq metres (34x14x.0929). As an aside the ancillary benefits include extra heat to the 3 adjoining rooms off the kitchen/dining room (once we leave the doors open) and also the 2 bedrooms directly over the kitchen/dining room are noticeable warmer than the other bedrooms. Therefore we have the rads in the adjoining rooms and the 2 overhead bedrooms turned down.

Re the damaged mesh our tiler advised us not to take up tiles as in his experience (and confirmed un-officialy by devi) tracing the break is not an exact science even using their "specialist equipment".


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## extopia (20 Mar 2006)

Ah, so you also have the oil burner on during the night. So the UFH is not the sole heat source in the room as the room is also being heated by the rads in the adjoining room. It would be difficult to establish the efficiency of the UFH in that case as it is really only ancillary heating.


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## Petal (20 Mar 2006)

This all makes a very interesting read! I might have to install new heating very soon, if the purchase of the house comes through. It's an old house and doesn't have any heating at the moment. It also needs to be rewired, etc. From reading this and other posts, is there such a thing as a condensing modulating combi boiler? I thought that would be the best thing to go with if the water pressure is sufficient. But reading about this UFH heating, would this be a good idea? I just want to run the heating as cost efficiently as possible, so any advice would be greatly appreciated. It's a small house, with two bedrooms and bathroom upstairs and an open-plan living/kitchen area downstairs. Will hopefully extend at some stage, but that's a while off.


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## UpTheBanner (20 Mar 2006)

Hi extopia,

the rads are never on the UFH room - there is no need, so the UFH is the main and only source of heat in the room. The rads are on in the adjoining rooms but we have them turned down compared to the rads in the front hall and the upstairs landing. The oil urner is timed to come on at 7am (after the UFH recharge). My guess is that heat goes from the UFH room into the others rather than the other way around. We experimented with the doors on the adjoining rooms opened and closed and with the UFH at lower settings when the doors were closed. The optium for our situation is with the doors open and the children walking on the tiles without us chasing them to have their slippers etc on.

To be honest we are totally surprised at how good the underfloor heating is but we were lucky (I wish I could claim it was due to our research) that the room is suited for it.


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## SPUDZ (20 Mar 2006)

forgot to say that it is devi mats that i am going to install, not the cable type. Will these mats be sufficient as the only heat source in the kitchen.(17sm) Anyone have experience of these?


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## z102 (21 Mar 2006)

*Re: electric UVH versus water UFH*

Before deciding for the one or the other heating system ALL relevant numbers should be included in the calculation.
UpTheBanner’s calculation gives us the number of €25 per bill and the heated surface of 44m2. These numbers on their own are not enough to be decisive.
The most important question is: How high is the heating energy DEMAND for the rooms that are to be heated?
With most existing buildings this number simply does not exist, neither in the form of a comprehensive calculation sheet based on assumptions nor in the form of a (measured) protocol.
So in this case all we only can rely on are the energy bills that we pay for, assuming that these are correct and taking for granted that there are no other influences in the energy consumption like for example passive solar gain, gain from neighbouring rooms and buildings, the building structure, insulation standards and personal preferences of the inhabitants.
And to compare such an energy demand assumption based on many unknown factors with that of another building can only be vague.
To show what I mean we can use UpTheBanner’s data, generously provided to us, thanks again for the points made.
The COSTS to heat a home are one major point but the demand of energy can be a different one.
Taking the numbers of €25.- per bill and the rooms surface of 44 m2
is leaving us with the pure consumer’s wallet question: ”Is it worth it?”
A fair question. So let’s have a look into the actual total bill: 
There is the €25.- per bill for night safer electricity supply.
Questions: Are these two-monthly bills paid over the entire year? Are these bills paid according to a budget plan provided by the electricity supplier?
Do the €25.- include the charges for the night-safer meter? And what is about taxes-the VAT?
Here the alternative calculation, please correct me if anything is missing or added twice:
€ 25.- per bill , 6 bills per year = 150.- 
Standing charges for the night safer meter € 10.48-, 6 times a year = 62.88
Resulting in a sum of 212.88
Plus VAT at 13.5% = 28.74
Total = 241.62
(This number does not include the government levy to support peat power plants)
So € 241.62 divided by 44 m2 gives us a cost sheet of € 5.49 / m2.
These € 5.49 per m2 is all we can rely on to compare one heating system with another i.e. is it worth it in terms of money.
An alternative to UF electric heating would be UF central heating fuelled with a condensing boiler running on LPG, since I use it myself let me compare the two in terms of money for last year’s/this heating season’s demand:
I buy around 1.000 l of LPG per year at a cost of € 400.- incl. VAT and government levy to subsidise environment destruction/ peat power plants.
My heated area is 96 m2, some of the LPG is used for cooking and domestic hot water, assuming 20 % of it. 
1000 l LPG minus 20% = 800 l LPG 
€ 400.- minus 20% = € 320.-
One boiler inspection per year = € 70.-
Electricity for the circulation pump for 240 days per year at 2.16 kWh/day
at general domestic rate of € 0.146 / kWh (240days x 2.16 kWh x 0.146 €/kWh) = € 75.67
Total €465.67

This results in a sum of € 465.67 / 96 m2,
or annual costs of € 4.85/ m2

So if our buildings and demands where the same then the savings for an LPG UFH compared with an electric storage UFH would be € 5.49/m2
- € 4.85/m2
= € 0.64/m2

So the UFH on LPG versus the UFH on electricity is 11.66 % cheaper to run. 
Or the UFH on electricity versus the UFH on LPG is 13.2 % more expensive to run.

Of course these numbers can’t be compared with each other in this particular case due to the lack of data about the actual demand, see above.

FUTURE impacts like price increases are not considered as well. One should keep in mind that most of our electricity is made from fossil fuels, and the ratio of converting a fossil fuel into electricity is worse than one to two. So if for example LPG doubles in price then the electricity prices would threefold.
Another future impact to be considered would be the technical developments concerning efficiency: A boiler like mine is oversized, therefore not the most efficient solution. At the time of purchase it was the most efficient, but technical developments never stop.
As well I could supply the heating energy with a solar panel/storage tank. Theoretical a warm water UFH system with a low output demand (kW/m2) could be running independently on solar panels/storage tank. Much easier and more economical to install then an electric heating UFH system that would have to be fed for example by photovoltaic cells or a small (maybe combined heat and-) power plant running on renewable energy like geothermal energy or bio fuel. This advantage is caused by the low energy demand for transmission of energy, bringing solar energy from the roof into the floor. The electric pump in a warm water solar system is the major consumer of electricity. 
But “savings on the pump” could be made also in the existing UFH system. There are already high efficient pumps available for around € 200.- (for example the Wilo Stratos Eco 30/1-5) which use only a third of electric energy to produce the same amount of pressure (“head”) compared to the old ones. 
So an UFH heating system running on warm water is easily converted to a different source of energy – if necessary it could be switched to electricity as well.
But an UFH system based on electric cables will always depend on the more expensive electric energy with no choice left.

P.s. Sorry for the formating.


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