Is it mad to put in under floor heating as well as rads?

[berlininvest]

Background
My brother in law is building a 2500 sq ft dormer house on a standalone site on his own land.

The problem
His head is melted trying to decide what heating system to go for.

The house
He is building his house to a high spec of wall, floor and roof insulation, with DG (e-glass and argon) windows which are more on the south/west aspect than on the north/east aspect. However, it would not be a passive house.
He has provision for 2 solid fuel stoves in the house, to burn turf, but these would not be the main source of heat for the house.

Preferred system for current conditions
As things stand, he favours an oil-fired condensing boiler with rads, on a timer, with thermostatic rad valves. He believes that he will need minimal amounts of heating to keep the house at a comfortable level because of the relatively low heat loss. I would imagine 1000 litres of oil would go a long way for him in the year. He wants the flexibility of the 'quick blast' of heat if need be that an oil boiler can give.

Doubts about 'green' systems
He is also dubious about geothermal or air-to-water at this stage. For geothermal, while there are examples of it working well, there are also many examples of it NOT working well. Also, if the geothermal collector pipes go wrong, it seems like a big job digging around to fix it.

Another major negative is the cost of electricity to drive the geothermal or air-to-water.

Planning for future oil prices
However, he is aware that the only way is up for oil, long term, and over the life of the house, oil could be very much dearer, becoming an even bigger part of the household budget.

At some point he might then want to change to some kind of 'green' technology e.g. one of the forms of geothermal / air-to-water to drive the heating system. Perhaps at that stage the technology will be bog standard, cheaper, and possibly grant aided or subsidised. However, he has been told that these would not be suitable for driving rads.

So, if he were to change from oil to geothermal / air-to-water, he would have to retrofit under-floor heating i.e. tear the house apart. Not really an option.

Make provision for UFH
He was wondering if it would be a mad idea to go ahead with the traditional OFCH system, with oil boiler and rads, but to also install the under floor heating network? At least then it is there if he decided to switch at some point in the future.

He is aware that this might be overkill, but wanted to check with the people on here as to what they think.

Questions
1. Would it be a lot more expense to install UFH that may not ever be used?

2. Is it technically feasible i.e. would the rads system get in the way of the UFH ?

3. Could he even have UFH mixed with a few rads on the same system?

4. Is there a danger the UFH system would corrode or degrade if it is not commissioned and in use?

5. Has anyone else done this or thought about this?

6. Would he be better to just use the oil boiler with UFH from day 1, and forget the rads, and then switch 'boiler' if he wants to down the line?

7. If he is to do that, how can he get the quick blast of heat he might want at certain times? Surely this is an issue for anyone with UFH?

8. He is also concerned that the UFH, driven by the oil boiler, would be less efficient than traditional rads run by oil boiler - would that be true?

9. He has heard horror-stories of UFH taking a couple of days to warm up, and then being too hot or too cold for the conditions at any given time. Could this be satisfactorily overcome with proper use of thermostats (inside and out) and timers?

Final points to note
Other points to note is that he is going with solar panels to help with hot water, he is surrounded by any amount of the finest bogland in Ireland, and he might also be tempted to put in a wind turbine at some future date (could be used to run another family home beside this one which also has a business attached). Maybe if he had 'free' electricity it might make the geothermal / air to water system more attractive.

Please give your advice
Thanks for reading this far. I know there is not a simple answer, in some ways there are too many choices.
It would be really appreciated if someone with knowledge and experience could look at this scenario and even say which options are definitely bad or which ones are more sensible.

 

[baldyman27]

I'm not a plumber though I am in the construction trade. I'm currently planning my own house at the moment and have been considering much the same. What I am going to do is to install UFH as my primary and make the provision for rads also, i.e., run all the pipes to the potential rad locations but leave them beneath the floor slab. I would also recommend leaving extra ducts out of the house base for future use, one of which could be geothermal.These are also very handy for future outdoor lighting, security gates, the list goes on.Its much less expensive to put them in at the building stage than at a later date, even though that might not be appreciated until you actually decide to utilise them.

 

[DavyJones]

Questions
1. Would it be a lot more expense to install UFH that may not ever be used?

2. Is it technically feasible i.e. would the rads system get in the way of the UFH ?

3. Could he even have UFH mixed with a few rads on the same system?

4. Is there a danger the UFH system would corrode or degrade if it is not commissioned and in use?

5. Has anyone else done this or thought about this?

6. Would he be better to just use the oil boiler with UFH from day 1, and forget the rads, and then switch 'boiler' if he wants to down the line?

7. If he is to do that, how can he get the quick blast of heat he might want at certain times? Surely this is an issue for anyone with UFH?

8. He is also concerned that the UFH, driven by the oil boiler, would be less efficient than traditional rads run by oil boiler - would that be true?

9. He has heard horror-stories of UFH taking a couple of days to warm up, and then being too hot or too cold for the conditions at any given time. Could this be satisfactorily overcome with proper use of thermostats (inside and out) and timers?

1 yes
2 no
3 yes
4 no
5 probably
6 personal choice, I would not install UFH
7 MAybe fit fan convector heaters EG Solo
8 In my experiance that is true.
9 More thermostats = more control.

 

[kemosabe]

I would agree with DavyJones in respect of installing solo convector radiators. They can be used with oil now & are very compatible with heat pumps in the future. I would not install oil with underfloor.

 

[berlininvest]

2 no

Thanks a million for the replies.

DavyJones, do you mean 'no, it is not it technically feasible' or 'no, they won't interfere'? Sorry for phrasing the question badly ;-)


Also, can someone explain what is a 'solo convector radiator' please? Do these run off the ofch or off the mains?

 

[DavyJones]

They won't interfere.
Solo are hooked up to wet system with an electric fan built in. they will work regardless of heat source I.E Gas/oil/geo etc

 

[berlininvest]

Thanks for that DavyJones.

I think part of the problem is that he can't see the wood for the trees at this stage.

It would be really helpful if those with experience of this stuff would take a step back and give a recommendation for him, based on his situation.

In other words, what would YOU do in this scenario, and why?

or even, what would you definitely NOT do, and why not?

 

[Buddyboy]

Well, we've installed rads and underfloor heating, running from an oil fired condenser boiler. The reasoning behind it is as follows

Underfloor - the sitting room and kitchen were too big for rads, and very open-plan so no walls to put the rads on.

Rads - in the bedrooms as we only need heat for about an hour before going to bed, and 1/2 an hour in the morning. Rads gave us this instant heat.

Oil fired - we are not on the gas line, so it was the easiest, and cheapest. A good condensor boiler was about 900 euro, but wood pellet stoves etc. didn't even come close (plus storage etc.).

The result, absolutely no problems. The underfloor works a treat, I've installed programmable thermostats in place of the static ones, so I can control the heat (within reason - it does take two hours to raise the temprature by 3 degrees - but the programmable thermostats allow me to not let it go below that anyway). Settings are 16 degrees at night (it rarely drops to that anyway), 20 degrees from 5pm (it works out when to turn on based on existing temps so as to be 20 degrees on time).

The rads work a treat. Bedrooms are hot when we need them and not when we don't. I can hit boost and heat them up when I want.

The underfloor manifold uses the 80degree water from the boiler and mixes it with the returning 30 degree water from the underfloor to ensure that it is 45 degrees to the underfloor. There is a TRV on the manifold that controls the mix.

Is it efficient? I think so, at least I am not burning any more oil than I used to. It is impossible to isolate the savings/costs, as we made hugh changes to the house, and there is probably more insulation, but more glass as well (and more open plan). Suffice it to say I am filling the 750 liter tank about every three months, which was about the same as the old house. 2000 sq ft. by the way.

I think most people get confused between the choice of heat delivery (underfloor or rads) and heat creation (heat pumps/geothermal etc). They automatically link underfloor with geothermal, and that is not the case. You can have underfloor with oil boilers, and rads with geothermal (albet bigger rads as they have to run at lower tempratures (like the solo ones mentioned).

Running a lower temprature underfloor system (typically 40~50 degrees) with a standard boiler (typically 70~90 degrees) may not be as efficient as possible, but when you factor in the installation costs it may work out cheaper in the long run.

By the way, one of the benefits that we hadn't thought of is that the new (under) floor is now a very large insulated slab, so when the sun shines in through our hugh windows, it heats it up very nicely and retains the heat for a long time (the upside of slow heat up times). So we get much more free solar heat than we ever got with out old house, with small windows and no insulation in the floor slab.

Any questions - feel free. I am not a plumber or builder, but learnt a lot more than I ever wanted to know about both. (And don't talk to me about septic tanks. !)

 

[berlininvest]

Buddyboy, thanks very much for taking the time to share your experience of this.

Really interesting to hear how you combined both UFH and rads in the one system, sounds pretty cosy!

[as a small aside, i honestly don't really think the thickness of the slab is going to make that much difference to the solar gain you get, any floor will have a far greater heat capacity than will be available from solar gain, so I don't think the slab thickness would be a limiting factor for most floors].

Maybe my BIL could do something similar to what you did.

Mind you, I know he is not really sold on the efficiency of UFH (and 750 litres every 3 months seems a little bit high for a well insulated house, unless you mean every 3 months for the winter?), and he likes the convenience of rads. I guess he won't want to run a less efficient system for 10 or 20 years on the chance that he might want to go geothermal down the line. On the other hand he won't want to be ripping up floors.

An alternative idea (based on the info you gave) is to just go with a standard ofch and rads system, and in the future if he really feels compelled to go geothermal, then put in rads that are more suitable for lower temps (e.g. the solo rads or bigger rads or whatever). At least then he is not ripping up the floors.

Or even go with standard ofch, but put in rads from day 1 that would be compatible with lower temps.

Any further thoughts anyone? What do you think DavyJones?

 

[Buddyboy]

We could not put in rads in the living room as it is 7.5m x 7.5x, with two walls completely as windows. We were digging up the floor anyway, so underfloor was an easy choice.

If I had a choice, after having experienced it, I would now definitely go underfloor. The heat is much nicer/consistent as the whole floor is 40degrees, as opposed to a rad at 70 degrees and waiting for convection to move that heat around the room.

But, whatever choice he makes, he should be happy enough as rads that are correctly sized for the room will be fine. The (normal sized) bedrooms we have work fine with rads.

And regarding the oil, yes this is over the winter. I don't expect to use any oil, or minimimal for water heating, over the summer. It's too early to say, as we only finished the revamp in August last year, but I would expect to use three tanks a year, two over the winter 6 months and one over the remaining six months. The rest of the house is cavity wall with blown insulation (it's a 40 year old house). And it's a bunglow, so heat lost is greater through the ceiling.

 

[berlininvest]

Thanks for clarifying that Buddyboy.

Interesting to hear that you prefer the comfort factor of the UFH, I guess if it is well regulated it should indeed be very cosy.

Anyone else got any views or ideas on all of this please?

 

[deadlyduck]

We installed UFH without rads in our house and use electricity as our sole energy source (air-to-water system).

Overall we're happy with the comfort factor and the annual bills (not quite in the house for 12 months yet) for a 3000sq ft house should come in at around €2500.

Our system allows you to regulate the volume of warmed water which is pumped through the UFH system and thereby maintain a pretty consistent temperature. At present, we have the heatpump/ stats set to deliver an average of 18.5 degrees and are finding it very agreeable- it was too much at 20 degrees.

Final word of advice- don't underdo the insulation. I'd really recommend going for more than the minimum.

 

[berlininvest]

Thanks for that Deadlyduck.

So that's 2500 euro for all electricity consumed?

And probably 1/3 to a half of that would be down to non-heating consumption I would assume?

So, if that guess is right, leaving about 1250 to 1600 euro for running air to water system for space heating and hot water?

By the way is it one or 2 storeys?

 

[deadlyduck]

Yes- the €2500 covers all electricity, whether heating, cooking or lighting. To be honest, I've no way of splitting the total cost between heating and other so can't give you any more info on that.

In our previous house (old, poorly insulated and approx 1100 sq ft, slightly over one third of the size of our new one) my records for oil + electricity over a 12 mnth period totalled approx €1800 (from memory). The real revelation when we moved was the massive improvement in heat retention due to the high quality insulation (we also installed chimney closures which possibly help www.chimneyclosure.com). In the old house, after switching the boiler off we'd lose heat within an hour. In the new house, heat loss is greatly reduced.

The house is a ground + first floor but also has stairs to the attic (which has usable space for an office and a junk storage room) so you could possibly call it a three storey?

 

[Decisions!]

berlininvest, thanks for all your questions - I have similar.

Buddyboy, thanks for your info, WoW! at last a solution for my needs.

We're building 2 extensions - one to either end of house (1) a dining/sunroom and (2) more bedrooms with ensuite (no we're not going up, we like the bungalow and have the space to expand). Existing part of house needs new radiators so were considering digging up the floors to retrofit UFH, but now I'm thinking it may be a good idea to combine the heating systems.

thanks again!

 

[Peter C]

Why not use a buffer store and link the stoves with the oil through the buffer to use the UFH from day one ? Except for heat pumps (geothermal / air>water) the buffer will allow him to add a wood pellet, gasifier even solar in the future. A big mistake I see with most UFH is people install everything needed, thermostats in each room, good manifolds with actuators controlled by the thermostats and then ruin the whole priciple by using a timer on the oil boiler. To work properly UFH systems need to get heat when it is called for, example on average a north facing room will call for heat more often than a south facing room if the boiler is on timer the room continues to drop temperature. If the boiler is on stand by it will be cycling to satisfy one area due to the flow and temperatures being low for UFH. Using the buffer it can hold heat like a battery so when each room needs heat it gets it without calling on the boiler and the result is a comfortable home with even temperatures to suit each room.