Key Post: Underfloor Heating

Re: underfloor heating

thanks Heinbloed!

a couple of further queries...
You say " you "can install u/f heating after window installers are gone" I thought that in the case of a new build the optimum time to install u/f heating is at foundation level as it is very messy job afterwards and difficult to get a smooth screed?? and every company i have spoken to say there could be problems/hassle if installed after. when did you install your system?
In my large living/ dining room i intend to have double glazing filled with argon,and well sealed doors and windows also this room will have an open fire (blocked up when not in use). However i also intend to have wooden flooring, for a few years this will be laminate as the house will be summer let (pay the mortage!) and then i would like to replace with solid wood when for my own use. what provision should i make at this stage????. As far as i understand i will be laying sub floor then insulation (think upgrading from min 50mm to 80mm high density TF70 kingspan) with u/f piping on top with concrete screed over. should i install battens in the screed from insulation layer to top of screed? this obviously would provide a means to attach solid timber at later date (once left in room to combat shrinking/expansion etc) but how does it effect heat transfer? does it help in any way? also some companies say the solid timber can be simply floated on the screed ??! I can imagine this is what is done with laminates but does it work for soild wood?
also, have you laid carpet? am trying to decide between carpet or wood for bedrooms......
Thanks for all help !!!
 
ufh

High JP Saltee!
The ideal situation to lay an UFH system in screed is when the doors and windows are in.Reason:The system needs to be pressure tested (the boiler as well)and the water in it could freeze(which should be no problem in summer).The second reason is that the screed could crack if exposed fresh to high air exchange and sun light.Windows can be closed and shaded if necessary.
After about two weeks of drying the screed the floor tiles can be put in place,the ideal method to glue them is a cement based mortar,if necessary a primer might be useful.The chemical glue would be "combed" on to the screed leaving air pockets between the tiles and the screed which in turn is neither good for a perfect heat transmission nor is it advisable due to shrinking.
Putting timber flooring-laminate or solid- on an underfloor heating that is already in a screed gives not only a high fuel bill due to the necessary increase in flow temperature , the screed might even crack if exposed to a to high temperature in the coils.
If you still have the choice than put some 10-20 cm of high density PS sheets under the building,before the ground slab is casted.
Check the home page of the company Aeroboard,as far as I remember they show how it works.
If you go for insulation ON the slab-followed by the UFH-than go for at least 10cm,better 15cm.The standard 50mm advised by the manufacturers of UFH are not enough in my eyes,they want to show picture that looks attractive in terms of investment.more insulation on the slab means additional height of the rooms.e. higher costs. I think the building regulations demand this 50mm amount of insulation in buildings anyhow without UFH,so you are better off going for some extra.On the continent where they have the same soil temperature as we they use about 20cm under the slab and 10cm min. under the screed.
Insulation is a once off investment,it won't be used up like oil or gas,it stays for ever with the building saving money as long as the building stands.And it is cheap.
The better way to install a timber floor on underfloor heating is to use heat deflector sheets which are placed on insulation sheets.These are strips of alumina with a dent in the center lengthwise .This dent will take the pipe and diffuses the heat over a larger surface.Check the home page of the company Qualpex,they show how it works.
Putting the pipe in screed AND covering with timber-which is a good insulator in it self!-would make the reaction time of the UFH very slow and the output very small.For the same reason the floor should not be covered with rugs or carpets.
Don't think about "floating" solid timber on an underfloor heating screed.Timber always "works",even on an ordinary cold screed solid timber should be fixed.Timber takes up moisture and expands when it is heated up , it will shrink when cooling down.The planks buckle and twist if not securely fixed. This effect won't be as bad if using artificial "timber" flooring,but also there it would be wise to fix it to the screed or on some battens.
Carpet or wood?Well,with UFH carpet is out of question,but some manufacturers of carpet flooring claim that they have also products for UFH.A natural timber floor always feels warmer on the feet than a cement or tile or PVC flooring.And it is free of hazardous chemicals that could come out when the heat is turned on.
When going for timber on UFH heating make sure the timber had been kiln dried ,that would take out some of the formaldehyde naturally occurring for example in spruce or pine.And try to source it as dry as possible.
 
Re: ufh

Some questions for Heinbloed

1.Does an UFH system not have some kind of antifreeze agent in it?
2.What would the primer achieve prior to a cement based mortar when laying tiles. What is the primer material?
3.You don't suggest any alternative to 'combing' out the chemical glue prior to tiling which causes air pockets and shrinking. Do you suggest simply not to comb it and float it out smoothly?
4.You speak of putting 100 to 150mm insulation under UFH. In practicality the vast majority of people can't do this, (yes it makes rooms higher - buildings taller - costs more - and takes great foresight which the average self builder wont have the knowledge for) but shouldn't you point out that the quality of insulation is not only related to its thickness. It is possible that for example a 65mm board with an efficient U value rating will provide better insulation that 100mm of aeroboard insulation with a poor U value rating ?
 
Underfloor Heating

thanks again heinbloed !

the system will be pressure tested but with air, this "testing" will be on while the screed is being poured so that any breaks will become noticable as air bubbles in the screed. No water will be in the system until boiler is connected. In my case i dont think the screed will really have any time to be exposed as the day it sets the walls are starting and as soon as they are finished the roof starts - I can cover with taurpaulin anyway.

The make up of the floor is a follows; hardcore, blinding, radon barrier & dpc,sub floor 4-5 inches, insulation 80mm of Kingspan high density polyurathane (i believe this is equla to 160mm polystyrene) u/f heating pipework with screed of 75mm on top - then flooring!

the heat deflector sheets seem to be unique to Qualpex, and speaking to them they only mentioned the sheets in relation to 1st floor level and screed for the ground floor! Every company and every person seems to suggest different methods for wooden floors: battens sunk in the screed to afix the wood OR floating the wood on top of corraguated cardboard OR glueing the wood to the concrete screed......so confusing! Really at this stage i need to decided whether or not to sink battens in screed. I'm starting to ask myself is u/f heating worth the hassle???
 
ufh

Hi kfpg1!
1.) No,an UFH system needs no antifreeze.If it was suspected that frost could reach the pipework than the pipework would have been badly installed-not insulated for example.May be you mixed up the Under Floor Heating which is installed in the house to give off heat
with the Geothermal Heating System which is installed under the ground outside of the house to collect energy.
2.)A primer prior to setting the floor tiles is not always necessary.But in cases where the screed is crumbly i.e.dusty it is.
3.)The alternative to combing the glue is indeed to set the tiles in a "bed"of cement based glue,also called "floating".Especially with the UFH system it is advisable,but also when using wall heating systems for example.
4.)The quality of thermal insulation depends not on its thickness but usually on its air content(there is also new vacuum sheet on the market but that is still not available to most of us).A high density PU foam has less
insulation(U-) value than a low density one from the same material,the same counts for Expanded Poly Styrene (EPS,Aeroboaerd).The high density material is used in UFH for its structural stability-you don't want to see the piano or the partition wall sink into the floor because the insulation "gives".
Now the best insulation material for UFH -well insulating but thin -is expanded glass foam.It comes in sheets about the size of aeroboard and it is Grey/black and quiet heavy,that would add to sound proof if necessary.But I have not seen it available in Ireland.
Polystyrene foam sheets come in different qualities,most manufacturers can provide you with suitable material to substitute the more expensive polyurethane sheets.
Demand the technical data sheet,it will tell you and your builder about U-values and structural properties like load bearing capacity.

To Jp Saltee !
The pressure test should not be relied on "bubbles in the screed".This method would not cover pipework going through walls or ceilings.A correct pressure test is done by applying some pressure and measuring it.Than a certain time has to pass-usually 24 hours-whilst the pressure is kept and than the number on the meter should still be the same as on day one.A builder that would cast concrete on an evtl.leaking pipe is a cowboy.What would he do if he really discovers bubbles?!Throwing out the entire screed before it sticks,damaging the pipework incl.the fixing battens and the insulation material with the aid of shovels and picks? Get a plumber in who will do a properly documented test,he will give you a "certificate of compliance ".If you get in trouble with your heating you can go back to the builder or claim money from your insurance or make the manufacturer liable.Your position would be better with some documentation.
And it is not expensive ,a job of a few minutes.
Don't sink battens into the screed to fix timber flooring on them.The entire construction would be to slow reacting,to cold to heat up the room.The heating pipes must touch the timber directly,timber is a to good insulator to loose out even more on warming up the screed.Qualpex is not the only manufacturer to use the heat deflector sheets,Unipipe has them ,others as well.The reason why they are not frequently used here is the extra cost involved for labour and material.
Each manufacturer from whom you buy the material will give you a free quotation on what you need.But you have to provide them with some facts,for example which flow temperature is the boiler providing.The flow temperature for a well insulated floor(the one covered in timber on top of the screed)must be higher than the flow temperature in the room without the timber floor.But your boiler has to provide it.If you need in one room a flow temperature of lets say 45 degrees and in the other room 35 degrees than the boiler has to burn a lot of fuel extra for these ten degrees.Further on you have to install mixing valves to supply the "colder" floor with colder flow water.This involves extra plumbing,additional risks of leakages and certainly extra costs. A 35 degrees system could be fed with geothermal heat or solar power at least for some of the time ,a 45 degrees system would need additional power to that.Since the UFH system will last for 50 years or more a builder should consider the increase of fuel costs and the consequences to the building being constructed.The strength of an UFH system lies in its ability to run on low temperature and to be maintenance free.Make the most of it.We could face a tripling of fuel prices within a few years and solar panels will become cheaper.With a well designed heating and insulation system you are well prepared for the future.But if you need 45 degrees in the floor heating loop then why going for floor heating at all,a well insulated building could be heated with radiators running on the same temperature reacting faster and being more economical to install.
 
Re: ufh

Heinbloed - for clarification purposes

1. New vacuum sheet = good insulation = not available
2. Expanded glass foam sheets = good insulation = not available
3. High Density PU foam / EPS / Aeroboard = strong but not good U value
4. Lower Density PU foam / EPS / Aeroboard = better U value not as strong
(what is PU ?)

In my situation
a.committed to installing underfloor heating on top of concrete raft downstairs and concrete hollowcore upstairs
b.planning to use as much tile as possible in house but with some timber flooring
c. with 150mm available from top of raft to bottom of doors

what approach to insulation materials & thicknesses / screed depths / floor fixing methods would you recommend?
 
ufh

Hi kfpg1!
PU stands for Polyurethane,the yellow insulation sheets.
With the specification of your ufh you better stick to the drawings of your engineer/manufacturer.All you have to ask them if there is a method to increase its efficiency or comfort.This could mean increased insulation (may be combined with a thinner screed).When installing the insulation sheets use two layers instead of one,you will have less gaps going all the way through.
 
Some other posts

Lilly
Unregistered User
Under floor electric heating?

was wondering what people thought of this option and whether they felt it was economical in the long run.

I am slowly doing up a 12 year old apartment which currently has basic electric heaters which need upgrading. Gas is not in the area, so I am stuck with electricity as the heating source. Am thinking of putting it under tiles in the bathroom and under carpet in the bedroom. The alternative is to replace the existing electric heaters.

Any thoughts would be much appreciated.....

Bob
Unregistered User
underfloor heating

I would advice you to stear clear of underfloor heating whether electric or water.
Depending on the lay out etc. of your apartment I would advise you do go for oil fired cnetral heating, all the pipe work can be run on surface i.e. run along skirting boards etc.
You have an option of indoor or outdoor boiler - a good brand name is Firebird. The outdoor one is about the size of a large dustbin no need for chimmney flue etc.
You will find that's it's the most economical in the long run and you will have gallons of hot water for domestic use. It can be set to heat domestic water only for summer use but be sure to fit a good copper cylinder for this purpose.

davelerave
Frequent poster
Re: underfloor heating

i'd advise keep it simple for renovation.go for oil-fired with outdoor boiler or maybe replace the heaters if it's all wired up properly for night storage

heinbloed
electrical underfloor..

I am afraid you have not many options unless your apartment has a chimney.Apartments build with electrical heating systems have been build using the cheapest method for the builder(initial costs) to leave the owner facing the bill on the long term.
There are only a few methods of heating an apartment that has no chimney or central heating system.
Electrical underfloor heating is one method,but again-cheap to install and expensive to run.
Something else would be bottled gas feeding a condensing boiler(room sealed system) that would heat up radiators.There are also small oil-fired condensing boilers available which have a very small tank that would hold enough oil for a month or so -ca.200l-in a tank the size of a cupboard fitting into the kitchen unit.The manufacturers claim that there is no smell of them.
(On the continent they even have boilers that run on methylated alcohol/ethanol.)
The problem with both of these combustion systems is a.)the installation costs and
b.)the limited fuel storage capacity-and therefore the purchasing price for the fuel
If you have any chance to convince the other apartment owners -maybe via the management-than you should opt for a central heating system supporting the entire building .It will certainly pay in the long term.
I am sorry I have no better news.

sherman
Registered User
Re: electrical underfloor..

I have electric underfloor heating in my rented apt. and was stunned when I got my first full ESB bill - it is an extremely expensive way to heat anything but a very small area. Avoid if you can...

askew70
Registered User
Question re DEVI underfloor electrical heating mats

I have read through this thread, and those linked to above, with interest, but I haven't seen much mention of the specific option that we are looking at at the moment. We are considering laying DEVI electrical underfloor heating mats under new floor tiles in our kitchen, and would appreciate any observations of those that are familiar with this particular (type of) product. The kitchen has concrete floors, and is north-facing. Right now there is one radiator in the kitchen which is just about adequate most of the time and more than adequate when the room is warm from cooking. We are looking at 12 sq. metres of DEVI heating mats.

We plan to replace the existing cork tiles on the floor with ceramic tiles, but wondered whether this might reduce the overall temperature of the room, hence the interest in the DEVI product. Does anyone know whether ceramic floor tiles, laid on a concrete floor in a north-facing room, are likely to have a cooling effect on the room? And if so, are the DEVI mats worth considering?

The DEVI marketing blurb is, obviously, enthusiastic about the effectiveness and economy of their product, but someone suggested to us that it is likely to be inefficient as there will be nothing to store the heat given out by the mats so the heat will "disappear" once the mats are powered off - which could make for a useful source of "instant" heat but would not be very economical in the long run.

Thanks for any advice or opinions.

heinbloed
DEVI

First of all:I have no experience with DEVI underfloor heating mats.
Think about insulation below the mats before you install them,with any underfloor heating system this is a must.
Most manufacturers recommend at least 50 mm of the better insulating material,if installing underfloor heating on the ground floor than at least 100mm is necessary provided there is no basement/cellar or already some form of insulation in place.
From your description I think a larger radiator-maybe a double or triple shell type- or a second one may be the better solution.Place radiators under the window where possible.
Electricity is the most expensive and polluting form of heating energy,see Irish Energy Center.
Ceramic tiles as such have no cooling or heating effect,they take up and release the temperature to which they are exposed to.But they feel colder to the touch compared to cork tiles.

askew70
Registered User
Re: DEVI

Thanks a lot heinbloed. Your advice has helped us to finally decide against installing the DEVI mats. I hadn't thought of the environmental impact of using electricity as a source of energy, but even if I had, we have a fitted kitchen in place which would make the installation of 100mm of floor insulation impractical. If we find heat to be an issue after the tiles are laid then, as you suggest, we will consider installing a second radiator or a bigger radiator.
 
Re: >>Underfloor Heating

Is it possible to have underfloor heating under carpet, I had hoped to carpet one or two rooms and the remaining rooms would either be timber or tiles.

Anybody used Nu-therm, Co. Donegal, or Warmfloor Heating Ireland in Omagh, i have asked these for quotes but would like to hear from people that used them for UFH or Geothermal Heat Pumps.

Heard a story about Geo Heat Pumps where somebody received their ESB bill and it was about €4000 for 2 months because some switch was in the wrong place so I would be weary about this!
 
Re: >>Underfloor Heating

No. Carpet on an under floor heating is no way to heat a room efficiently . And that is the aim of an UFH. It would insulate your floor in the wrong place . Try to heat your room with a radiator wrapped in carpet. Some carpet manufacturers claim to have the carpet for UFH - I haven't seen it working yet .

About the geothermal pumps check the other posts. Check out as well the home page of the IEA -that is the international energy agency . And you will find out that these things called geothermal pumps here in Ireland aren't the real thing. Just a sales gimmic to fool the inexperienced buyer. See http://www.iea.org/

A geothermal heat pump draws the heat stored in the planet . What they sell here are slow reacting over dimensioned expensive solar collectors .Exploited by the means of a heat pump . They make your land useless for any further development . Be it an extension or a sewer , an arboretum or a swimming pool. The space is lost , except for a lawn maybe . Take the costs of the land into your calculations as well . And you have to put them on the south side of your house because of shading . No trees and buildings in their vicinity.
 
Re: >>Underfloor Heating

Out of interest Heinbloed if the heatpumps which are been imported are european and are used in Europe how are they different.
The reason I ask is that on the majority of cases that I have seen for Geo the heatpumps are coming in from the continent directly, are you saying that they are changing the heatpumps here in some way? do you have any evidence of this?

Taking the costs of the land into consideration is a bit of a broad statement, you own the land and it is not a case in the majority of cases that you will build on 100% of your site, therefore there will be vacant land and you own it anyway, it is not a case of buying a site for the exact size of your house.

What are the difference between the heatpumps in Europe and the heatpumps here?
 
Re: >>Underfloor Heating

. Heat pumps are heat pumps. Technically spoken . But here in Ireland the technical knowledge of the would -be- costumer allows for some nice looking additives . For example the term " geothermal heat pump ".

The term " geothermal " is strictly reserved to heat from the ground . In the scientific/technical world this is heat stored in the crust/body of the planet earth .

Here in Ireland they use this term in any case for any heat collected from the ground . Which is technically wrong. But who minds ? Somewhere else competitors and consumer organisations would have coursed and brought the culprit to court...

Heat that is derived from the sun is called solar energy. Nothing else .So a flat shallow heat exchanger dug into the ground makes use of the stored solar energy . Once this is exhausted it has to switch off and wait for a few warm month to warm up the media , the soil . Not so the geothermal energy exploiting system. Be it a heat pump extracting the heat or a direct fed hot brine/water system , lets say a hot spring in that case . There are entire nations depending on geothermal heat pumps , Iceland for example .

A real geothermal system needs no sun to get warm . That is the difference . If you had a real geothermal heat pump installed in your back garden than the points I made above ( shading etc. ) would not bother the efficiency of the system . Just a borehole delivering heat for decades . That's the difference .

Always include all costs . Also the cost for court cases against your neighbors who's trees and buildings are causing shading , who's wells and foundations might influence the efficiency of a so called " geothermal heat system " .And also the costs of plan B . When you can't forbid your neighbors casting shade on your property .

A solar panel/tubes will be much more versatile. If the panel is not good in one place than bring it to another . A few meters of extra pipe laid in an afternoon. No court cases , no trees to be chopped. Peace . And if you move than take the panel/the tubes with you . No problem .Try this with one of these so called ....digger employment schemes ?
 
Re: >>Underfloor Heating

Re insulation for UFH, SEI has advised me that instead of increasing say the insulation on the ground that it would be of better value to increase the insulation in the roof, as heat rises.

re screed. Has anyone used easy screed or a similar product for over UFH. It uses only 35mm screed instead of the normal 75mm. I was advised that using 35mm will allow the temp to be controlled more. Also any idea of cost, would it be more expensive than the normal 75mm screed.

Is 6'' space between subfloor and finished floor sufficient when installing UFH and using say 60mm insulation. Will use 20mm floor boards.
 
Re: >>Underfloor Heating

thinking of underfloor heating in my kitchen (under timber or laminate). I know lots of details would be required for a more accurate guestimate but would anyone be able to give me a v. v. rough estimate of cost for area of 4.5 X 3.5 meters?
 
Users of underfloor heating: what settings?

This one goes out to anyone who is experienced in using UFH in their homes.
Basically I am trying to get the most fuel efficient usage of the system from all of the adjustments that can be made. What do people out there generally do regarding the following?

Room Thermostat Controls (digital in my case)
Leave at 18 to 20 degree range ? - use time profiles to have slightly warmer morning and evening during occupancy and cooler during night and working day ?

Supply or Flow Temperature Coming from Boiler to Manifold
I can set this to whatever I want - is 45 degrees enough?
If I go higher or lower does this just increase / decrease the rate at which rooms warm up? i.e. responsiveness. If I go too low on supply temp does the system struggle in some other way

Taps at the Manifold for each Individual Pipe Loop
What do people do with these again isn't this about responsiveness e.g. fully open = faster heat. If so aren't these and the supply temp above giving similar control?

What's the best balance for all 3?
(I appreciate homes are different in terms of insulation and personal tastes differ BUT what works for you especially re:fuel economy)
 
Re: Users of Underfloor Heating: What Settings?

During the working day (assuming you're not there) you can/should turn it right down (I think the recommendation on the UFH in my previous place was 10c, although I used to just turn it right off) rather than leave it at 18-20c. No point heating an empty house!

I don't know about others, but I found UFH to be very expensive.
 
Re: Users of Underfloor Heating: What Settings?

My own experience differs miles from Sherman's. Cooling your house by setting the flow temperature to 10 degrees - why ?

First point : What sort of UFH have you installed ?
Second point : What flow temperatures does your boiler allow for ?
Third point -and propably most important : Is the system adjusted ? At the manifolds - there are two of them (flow and return ) - you will find little "meters" showing the rate of flow in liters per minute .At these little gadgets your heating economy depends on . When having all circuits working for let's say an hour or so then the temperature of the " return water " at each of them (meassured at the return manifold ) should be the same -no matter how big or small the individual heating zone is .You can meassure the temperature at these "return manifold inlets " ( I don't know of any better expression, hope you understand ) with a thermometer. Either a simple outside/inside thermometer where you place the outside probe with the aid of some cellular tape directly to the relevant brass joint or with a more sophisticated laser thermometer as used for example in the food industry .The process is called " hydraulic adjustment " .
As long as these temperatures are equal your system is set at the best point . For economical reasons it generally should run at the lowest possible flow temperature.You won't save money by switching it off at night time , the opposite might be the case. At least not in winter. Some boilers allow for a "reduced night time temperature" which you can set your self at the timer .If your UFH is the standard concrete floor than this might not be necessary , depending on the quality of the concrete and the covering . The slower it reacts the less sense it makes to adjust the flow temperature for different times.
When going for a fully automatised system an outside sensor with memory would be " the dot on the i " - making the system fool proof .These sensors are new to the Irish market , check your boiler manufacturer if they can be retrofitted. Usually that is the case with most boilers , but it might take ages to justify the extra expenses . But with the increasing fuel prices in mind you never know- money saved today might cost twice as much tomorrow to save it .With a (home) sellers point of view go for it .As a home occupier - I don't know.
 
Re: Users of Underfloor Heating: What Settings?

I use UFH for 2.5 hrs in the winter per day.I use 850 lts a year in an 1800 sq. ft house.I have extra insulation throughout, particularly walls and roof,paid for itself in two years. Re thermostats in each room: Keep unused Bedrooms set at 16 degrees.used bedroms at 18D,Hall at 18D,Living areas in general at 21 or 22 D. Only turn on heating at, say, 16.00hrs. for the no. of hours you require to have the living areas comfortable, particularly at night.(in my case this is 2.5 hrs.), as the heat is held in the floors etc and is slowly releasing same until heating is turned on again. In this country you do not need an external heat controller.Have main control valve set at 50 degrees, does not need to be adjusted.In the rooms where there is no usage,the 16 D is ample once you keep their doors closed.Some obvious but much disregarded guidelines:Eliminate all draughts. Keep external doors closed at all times(also windows closed except where necessary to have open, say in a bedroom at night)Always pull the curtains in all rooms as soon as practicable each evening. Check attic insulation again! Is there at least 10 inches of well fitted fibre glass in place?A more drastic step can be taken to improve overall insulation (where only the cavity wall "insulation" was installed originally, is to retro install an inside layer of polyurethane backed insulation board, with the plasterboard finish facing into the rooms (8 ft x 4 ft.sheets). These can be skimmed and plastered where necessary and are really the answer to poorly insulated buildings. It makes sense to have your insulation in the room rather than allowing any heat in the house to evaporate through concrete walls where poorly fitted polystrene is supposed to stop the heat from getting any further. It simply does not work no matter how well the builder tried to do a good job, and how many times does that happen? Hope this helps you in some way.
 
Re: Users of Underfloor Heating: What Settings?

Whatever you do, underfloor heating is EXPENSIVE !! We have an oiled fired Boiler and the house is 2650 Sq Ft. We have 6 zones on the ground floor and radiators upstairs. 2 zones are very rarely used and I have them set to 10 Degrees all year round. The other zones I set to between 18 and 20 Degrees from October through to April, I then turn them down to 10 purely to save money !

I just leave them at the set temperature. If you switch off in the morning and switch back on in the evening, the floor slab will eventually cool and you'll spend more money reheating it. In theory the most efficient way is to leave at the set temperature and UFH will kick in and out as required.

One of the problems is that if you leave your door open for even a few seconds, the cold air triggers the thermostat and off you burning oil again, same for windows.

If I could do it all again I would not install UFH !! We're burning approximately 3K / 4K Liters from Oct to Apr.

An interesting product that is supposed to cut costs is Oxyvent, see http://www.oxyvent.com/ for details. It claims big savings by removing air bubbles, allowing water to return to the boiler much quicker, therefore losing less heat and requiring less reheating !
 
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