Underfloor heating running costs - help


The concrete 'slab' should be kept as minimal as possible..... at most a 75mm screed should be used, and if possible an 'easy screed' type should be used.

The external walls should be made of a material that will instantly redirect the heat back into the rooms, ie SIP panels or ICF walls.... even insulation backed plasterboard.

Its all about improving the responsiveness of the heating system.
And dont install UFH is you have passive ventilation.
 
Hi,

Question for sydthebeat. OP excuse me for jumping to a different question. Sydthebeat - if you were building a house yourself, highly insulated and highspec windows and for ventilation HRV - would you install geothermal heat source or would you go for good condensing oil burner? Would apprciate your expert opinion. The building material aim to use is poroton block and clad in natural stone.

Many thanks angela59
 
anglea, if you can get your house to as close to passive standards as possible then it really doesnt matter how you heat it. Thats no a flippant answer.. ill clear it up a bit.
We all know the pros and cons of oil vrs geothermal vrs wood pellet etc.

If you have an extremely well built, high spec, even passive house then it will require a minimum of heating...... geothermal may actually work out to be uneconomical (initial installation cost wise) when compare to the output required. Oil will always increase in price and whilst cheap to incorporate initially, there are better options.

If you have a 'close to' passive house i would try as best i can to design a solar collector based heating system, with a wood pellet boiler, as back up only, and perhaps a wood burning stove with back boiler, serviced by a double skinned flue. People do not appreciate the actual gains from passive solar design... a dwelling well designed with these principles, and well constructed, can be heated for 7-8 months a year free... thats not an exaggeration.

ennisjim.... passive vents allow fresh air in at 'outside' temperatures... for example last week probably 1-3 deg c... this needs to be heated up to 21-22 deg constantly....
depending on external wind conditions a passive vent may change the air in a room completely in possible 1 1/2 hours... therefore, on a cold windy day, you need to heat the room completely from 2 - 22 deg c every 1 1/2 hrs... and this assumes no other exhaustion of air through the building envelope... which of course will exist anyway.
HRV systems will heat the incoming air to approx 14-16 deg when exhausting 22 deg stale air.... this makes a huge difference to heating costs.
UFH works on a lower temperature than rads, so if it is made to work harder to heat cold incoming air it becomes less efficient, and therefore i dont recommend UFH with passive vents.
 
Hi Sydthebeat,

Thanks for reply and value all the information you supplied.

Angela59
 
Thanks for clarification sydthebeat. It would be nice to install HRV but quotes for approx €7000 decided that for me. Hopefully it will get cheaper.

At the same time, I know several people with UFH and none have HRV and they are happy with UFH - though maybe they've just blocked the ventilation holes in their walls !
 
We have HRV and UFH downstairs - there is a dedicated (gas) condensing boiler running this. We've had the heating on 24x7 at the lowest setting on the 'stat for each zone since we moved in - the boiler seems actually to be on about 20% of the time. We have insulated boards on the external walls, lower u-value glass, extensive S and W glazing and 100mm TF insulation under the screed.

I'll post the running costs when we get the bill!

SSE
 
Hi,

Could anyone recommend a good wood pellet boiler to run ufh and also if anyone has good experience of HRV unit.

Thanks in advance, angela59
 
whatever wood pellet boiler you get, be sure that it is modulating, ie give the amount of heat you require at a given time. We have a Windhager and are delighted with it. All the best whatever you decide.Optimstic
 
Hi Optimistic,

Funny just reading through your previous posts just a minute ago, we're gearing towards wpb having previously geared towards geothermal - the initial outlay on geo is very expensive and when you are trying to build a house to a high spec something has to give along the way so I'm glad of all the advice. thanks optimistic
 

If you thought Geo is expensive wait until you get a price for the windhager. They wanted the bones of 20K from me and this didn't include the plumbing!

On HRV you could talk to www.atc.ie. They sell a vortice model which apparently scores the highest efficiency rating on the british SAP system. They also sell the ducting system which was also tested. Its quite inexpensive but is a self install which might be off putting. Usual disclaimer, no connection with ATC.

Incidently, I'm told that virtually none of the HRV systems available at the moment in Ireland have an efficiency rating that can be used in the DEAP software for you BER certificate i.e. they are not tested by an independent body as yet. You will be stuck with the default efficiency. This may not matter to you of course. The SAP ratings can be used however. Sydthebeat can confirm this of course but this is what I was told by a BER accessor.
 
Hi sas,

good to hear from you again. The windhager certainly sounds expensive 20k is a lot - optimistic quoted 11k though he knew the guy - this figure may not include installation. Will have to research a bit more to see if there is anything as good as windhager but not as expensive. thanks for advice SAS. By the way SAS did you get any further quotes for windows or at leas any better than the E46,000 or thereabouts that you were last quoted. Would love to know.

many thanks angela59
 
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I spoke to the same guy optimistic dealt with. Optimistic got his a while back and plus you should keep in mind that the greener homes scheme is very likely to disappear underneath us any time now so unless you have grant approval, don't include that in the costing either. There were other little nuggets too like you had to be willing to commit to a €150 per year servicing contract for 5 years or it affected the guarantee!

Seeing as we've hijacked this thread I'll take the rest off line with you.
 

There is a facility to input the manufacturers declared efficiency.
The default is 66% with a power requirement of 2 W/l/s.....
Once the 'declared' values are in accordance with an approved calculation method then there is no problem using them.

It is worth noting that using a HRV reduces the effective air change rate from 0.5 ac/h to 0.17 ac/h... which is quite significant on a high spec low energy dwelling.
 
PAYEPLEB, love the name by the way....

You have done the most important thing right already..... the HRV systems is a must... the insulated slabs on the inner leaf is also a good idea once they are installed correctly. If they are just spot daubed then there may be 'thermal looping' problems as an open cavity is formed behind the slabs. If they are continuously 'ring' sealed then they will be fine. If they are daubed then i would consider taping up all joints, giving particular energy to taping up ceiling / wall and floor / wall junctions. A skim finish over this should create a fairly air tight construction.

Once your construction is airtight and well insulated, then whatever heating system you use will not be running inefficiently. The 'greener' client would install a wood pellet burner now, by these technologies may not be perfected yet. The solid fuel stove is a good idea, but one thing that is certain is that solid fuel and oil will rise in price..... at least you have the option of converting in the future.

UFH heating works best with either geothermal or solar collectors. UFH and oil is not an efficient system.
 
yes is the answer to your question....
Thats the very system my parents have... solid fuel stove in kitchen heating centrally, with oil back up...

They hardly ever have to turn the oil on, but its designed so that if the oil and stove were lit at the same time, the oil would heat the system until the stove was heating to a certain level, then the oil would click off and the stove would be the main heating system. So both systems could actually be 'on' together but both would not heat at the same time.

How is your insulated plasterboard fixed to the walls???
 
PAYEPLEB said:
Haven't started yet as house isn't covered and no windows in. I'd say i'll be fixing it directly onto the wall and taping any little crack or opening I can see
Click to expand...

Just remember to create a continuous bond at all junctions, especially floor and ceiling, leave no gaps. If you do this you can actually trap air which will act as an extra insulator as well.
 

given that we don't float in mid air, and walk on the ground, that's a bit moot....

I couldn't disagree more about rads. They are fundamentally flawed, promoting convection (.i.e 'draughts') by dint of phyics - heat rising, and all that.

So, from the rad, air has to rise (along wall/window ), across ceiling, and down the other side of the room. Essentially, it is heating the space from the ceiling down. Again, with me being only 1.7m high, that's no good to me.....

UFH on the other hand, heats from 'ground zero'. From the minute it radiates heat, it heats the person (by conduction, through contact), and heats the air from the floor up - iow, where you're more likely to find people/cats/dogs/life..........

And you're forgetting that other benefit: you are not confined to placing the couch/dresser etc,as all walls are 'free'. Walls with rads, on the contrary, are limiting in terms of furniture placement, but even more importantly, are limiting by dint of having the convection current of air interfered with by furniture position - so, you can't put the couch in front of the rad etc etc. without interfering with the heat quality in the room.

I mean, how many of us have seen people sitting/hogging the rads? Exactly, it's because the heat is all in the wrong place.

And then there's thermostats: 'stats on the wall for rads can be hopelessly useless, being affected by poor placement and giving inaccurate results. In a house with HRV, it's even worse - I've seen one located near the air input, so it was being 'chilled' by incoming air, so room was constantly too cold. TRV's, although better than nothing, also suffer from being below the heat source. The whole room has to heat up first, from ceiling down, before they are effective - by which time, it's too late.
 
PAYEPLEB - one thing you might want to do is add in a couple of extra pipes to the loft area and get a tank with an extra coil - just in case you want to get solar at some point in the future. It'll likely be easier to do this during the build.

SSE
 
When discussing the merrits of different types of heating systems one should always compare them on the basis that they are correctly installed.
 
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