Ground Source vs Pond Source vs Air source

[MikeNeaverson]

I'm in the process of completely renovating and extending an old cottage to make a 200m2 property. It will be insulated to modern building regs standards but nothing OTT. Planning on underfloor heating downstairs and radiators upstairs. We have an acre behind the house that is a silty clay loam and will otherwise be used as a garden/paddock.

My other half would like at some stage to dig a large pond as part of this garden. I understand that water source heat pumps are more efficient than ground source. Anyone know how big a body of water I would actually require to make use of this? What would you do? Just go for ground source?

I've been advised that a 12kw heat pump would be roughly the right size.

Or shall i just bin this whole renewable idea and put an Aga in???

 

[Exfarmer]

You should take serious advice on this, to get it wrong will be expensive.

 

[Hawkes]

We put ground source in our new house 2 years ago and it has worked well. I am not sure radiators are right for ground source or water source, the operating temperature is a lot lower than your ordinary oil or gas fired boiler. We put underfloor up and down, the house is well insulated and it is most economic to set it at a set temperature and let it maintain it. The only surface heat is our towel rails and they are dual fuel so they can be electric only in the summer. You need a big capacity insulated hot water tank, as for example running a bath you will run mainly from hot tank with a dash of cold because of overall lower temp. So radiators wouldn't get hot like you would expect. The key thing is getting the insulation as good as you can and the building airtight. We have a heat recovery system that runs with it, recovering heat from the hot rooms as it ventilates the house. In the summer it can cool.
We got a lot of conflicting advice and some eye watering quotes, some of them from people who seemed to know less than me (not much) so be careful there are a lot of get rich quick merchants in that game. Ours isn't perfect, I would do some things different now but it is brilliant in the winter.Especially after 65 years in a draughty cold old houses before!

 

[steveR]

We put ground source in our new house 2 years ago and it has worked well. I am not sure radiators are right for ground source or water source, the operating temperature is a lot lower than your ordinary oil or gas fired boiler. We put underfloor up and down, the house is well insulated and it is most economic to set it at a set temperature and let it maintain it. The only surface heat is our towel rails and they are dual fuel so they can be electric only in the summer. You need a big capacity insulated hot water tank, as for example running a bath you will run mainly from hot tank with a dash of cold because of overall lower temp. So radiators wouldn't get hot like you would expect. The key thing is getting the insulation as good as you can and the building airtight. We have a heat recovery system that runs with it, recovering heat from the hot rooms as it ventilates the house. In the summer it can cool.
We got a lot of conflicting advice and some eye watering quotes, some of them from people who seemed to know less than me (not much) so be careful there are a lot of get rich quick merchants in that game. Ours isn't perfect, I would do some things different now but it is brilliant in the winter.Especially after 65 years in a draughty cold old houses before!

No arguments with any of this. Wish I had a heat recovery though....

When the OP sizes your DHW tank, make it as a big as you can possibly fit in the space! Ours is 300l and I still cuss I did not insist on 5-600l. The additional capacity is always worth having, and will make better use of other nergy sources such as PV or solar thermal in the summertime.

I know of one old cottage that was converted and they used UFH downstairs and rads up. I was unconvinced about the coil ground loop install when I saw the system, and it turned aover couple of years, to be waaay undersized and the system was using electricity to buffer the shortfall in cold weather. Rads were too small as the plumbers fitted larger standard rads, and not suitable for the low temps of a heatpump output.

To the OP, I am sure I saw an article about a job being done using a mixed ground/underwater loop, all using the same pipework. Cannot believe it would be an issue feeding from several loops into a manifold...? Dig or lay the loops in under the new pond?? When I put ours in, I asked for extra ports on the manifold, "just in case". 10 years later, it looks as if the sizing was correct

As Exfarmer says, find an expert!! NO to an Aga though!!!!!!

 

[br jones]

We put ground source in our new house 2 years ago and it has worked well. I am not sure radiators are right for ground source or water source, the operating temperature is a lot lower than your ordinary oil or gas fired boiler. We put underfloor up and down, the house is well insulated and it is most economic to set it at a set temperature and let it maintain it. The only surface heat is our towel rails and they are dual fuel so they can be electric only in the summer. You need a big capacity insulated hot water tank, as for example running a bath you will run mainly from hot tank with a dash of cold because of overall lower temp. So radiators wouldn't get hot like you would expect. The key thing is getting the insulation as good as you can and the building airtight. We have a heat recovery system that runs with it, recovering heat from the hot rooms as it ventilates the house. In the summer it can cool.
We got a lot of conflicting advice and some eye watering quotes, some of them from people who seemed to know less than me (not much) so be careful there are a lot of get rich quick merchants in that game. Ours isn't perfect, I would do some things different now but it is brilliant in the winter.Especially after 65 years in a draughty cold old houses before!

May i ask what roughly is a years electric bill? As i am on this path and undecided which way togo ,and all information is most helpfull ,tia

 

[Mur Huwcun]

We’ve got groundsource for a 4 bed house, half new built, half old stone draughty construction. Underfloor throughout ground floor, rads upstairs. rads are hardly used really. 100m Trenches in field not loops to gain maximum surface area. New build part is lovely and warm all the time with the floor never really feeling that warm, old part takes a bit more heat but bar any serious easterly wind is always ok. Insulate and seal every nook and cranny you can. Although not really recommended go around your old part with expanding foam around every floor joist that goes into the walls etc and stick some earthwool insulation everywhere, it’s much easier to open a window for a good airflow! duct any cable or pipe that goes through a wall so you can stick insulation around them And seal all skirting boards etc. We’re still plugging gaps here!!

Our DHW cylinder is only 300 ltr, never ran out of hot water at economy mode but the HP screen lets you programme in high demand times if need be plus every max 14 days water goes up to 65 degree to eliminate legionella so 7pm on a Sunday is a goid bath time!!!

Not up to date with RHI now but our system is 4 yrs old and was well worth fitting, the payments will pay for the install, plumbing, cylinder, underfloor, room stats etc. So if say the system breaks down in years to come I could just connect a boiler to the three pipes where the HP is now.

Electricity cost for us is average at around £100-120 a month for everything. We were paying £80 a month for dual fuel for the old house so don’t think it’s excessive. One thing we have that the installers were not keen on is a log burner in lounge which we use a lot at weekend etc and has been a godsend during power cuts.

 

[Hawkes]

May i ask what roughly is a years electric bill? As i am on this path and undecided which way to go ,and all information is most helpfull ,tia

Everything in house is electric. 9kw Kensa heat pump, UK made. Approx £400 a quarter summer and £500 odd in winter. The heat recovery uses a bit as it runs 24/7.
4 bed house.
The RHI pretty much covers it, not sure what the rates are now for current builds. It has almost passive house insulation values and that is where it is worth spending as much as you can in the build..

 

[Ukjay]

Personally I would seek proffessional help with calculating this, as you will potentially need a large volume of water if you are making a pond - plus I would hypothesise you will need depth to avoid the water freezing as you draw heat from the water in the winter.

The systems 'can' work with utilising Emmitters (radiators), however it needs a different mindset to the traditional radiators need to scald you mentality or the system is not working correctly viewpoint. These systems are designed for more subdued heating output requiring the system to be on longer to attain the temperature required within the home, and some state left on continuous at lower temperatures as they say it reduces energy required.

One common problem is that a lot of people do not realise, or potentially understand the methods needed to calculate the heating system correctly hence why they say / feel emmitters (radiators) cannot be used.
It is here that you need to find someone who understands and can can carefully calculate the fabric losses, and who understands the 'F1' factors, whereby they can then calculate the MFR, design the F+R ∆t, MWT, Target Air Temp you are working on for the room and the MW/AT differential ∆t for the system in order to understand the emmitter / pump sizes etc.

They will possibly use Glycol based mix in their system as it would probably be closed loop, so the SHC of the fluid is different to that of pure water, so it normally requires higher flow rates from the circulator as a result in the same system.

Emmitters (radiators) listed to buy are normally rated at ∆t 50 (The common 70/50 Design) and some still show some at ∆t 60°C, which is not always taken into consideration or understood by some when replacing heating systems, hence why people sometimes say their home is cold and does not get to temperature etc after a new system or radiator is installed, because the emmitters (radiators) installed are not correctly rated if these considerations are not factored into the replacements.

In the case of the WSHP, they will more than likely be operating at the lower MW/AT ∆t, so the emmitters therefore will need to be sized larger to provide the required heat output, as I believe you may still require the 20°C ∆t for the F+R.
I hope this helps.

 

[br jones]

Everything in house is electric. 9kw Kensa heat pump, UK made. Approx £400 a quarter summer and £500 odd in winter. The heat recovery uses a bit as it runs 24/7.
4 bed house.
The RHI pretty much covers it, not sure what the rates are now for current builds. It has almost passive house insulation values and that is where it is worth spending as much as you can in the build..

Rhi is very little now ,so its a knife edge decision on which way to ho

 

[snarling bee]

Just put in an oil fired AGA and be done with it.

 

[Doing it for the kids]

Just put in an oil fired AGA and be done with it.

Aga are awful to deal with.

get an everhot, cheaper to buy, cheaper to run, bigger to cook on, half an hr to install, controller-able to 1 degree - all round wife pleaser

 

[MikeNeaverson]

Thanks for your comments all. I have asked two companies to quote, though interestingly I think they are both speccing different size systems having both been given the same building plans.

 

[EBF]

Following with interest. I received a spec for a gshp in a new build from a specialist renewables company and asked for quotes to install it from 5 contractors. They all said it was under sized!

@nev12345 would you be willing to update us on spec and quoted cost in due course? TIA

 

[MikeNeaverson]

I will do... though I've now asked three companies to quote and I haven't had anything back from any of them in a week.

 

[MikeNeaverson]

Two companies have returned quotes, they have both estimated heat loss of the property based on the technical drawings as the same.

One has specced a 12kw and the other the 13kw unit, but I think the difference is only because of units within their range.

Very little difference in prices, about £13k + VAT for supply only of the single phase unit, hot water tank, pipe work and accessory hardware for ground arrays. So bearing in mind that I’ll otherwise be buying a new oil boiler, oil tank and hot water cylinder, the additional cost is roughly £10k

 

[br jones]

Everything in house is electric. 9kw Kensa heat pump, UK made. Approx £400 a quarter summer and £500 odd in winter. The heat recovery uses a bit as it runs 24/7.
4 bed house.
The RHI pretty much covers it, not sure what the rates are now for current builds. It has almost passive house insulation values and that is where it is worth spending as much as you can in the build..

So thats around 6to 800 a year extra in elecy.

 

[Ffermer Bach]

We put ground source in our new house 2 years ago and it has worked well. I am not sure radiators are right for ground source or water source, the operating temperature is a lot lower than your ordinary oil or gas fired boiler. We put underfloor up and down, the house is well insulated and it is most economic to set it at a set temperature and let it maintain it. The only surface heat is our towel rails and they are dual fuel so they can be electric only in the summer. You need a big capacity insulated hot water tank, as for example running a bath you will run mainly from hot tank with a dash of cold because of overall lower temp. So radiators wouldn't get hot like you would expect. The key thing is getting the insulation as good as you can and the building airtight. We have a heat recovery system that runs with it, recovering heat from the hot rooms as it ventilates the house. In the summer it can cool.
We got a lot of conflicting advice and some eye watering quotes, some of them from people who seemed to know less than me (not much) so be careful there are a lot of get rich quick merchants in that game. Ours isn't perfect, I would do some things different now but it is brilliant in the winter.Especially after 65 years in a draughty cold old houses before!

I was listening to the today programme a couple of years ago and they had a chest consultant on, saying modern houses were too air tight, and needed windows open to allow a flow through of air and ventilation to stop respiratory problems, so we have one branch of government advice saying air tight houses while another says ventilation needed. I know you could say heat recovery system allows for ventilation while not losing expensive heat, but I am always dubious about anything that requires mechanisation (I know we have lots of it and can't do without it) and prefer systems that are designed to operate without intervention.

 

[24/7 farming]

12kw ecoforest heat pump running in our new build for coming up on 4 years. Average annual usage is in around 4000kw for all heating and hot water (on our electricity tarrifs it works out at just over €500 a year)for a 250sqm 2 storey wit all floors concrete and underfloor. 600m of outdoor loops in 100m runs bac to manifold.
Everything running of stats for rooms and hot water. Never have to think about it.
Do hav mvhr also.

 

[Highland Mule]

I was listening to the today programme a couple of years ago and they had a chest consultant on, saying modern houses were too air tight, and needed windows open to allow a flow through of air and ventilation to stop respiratory problems, so we have one branch of government advice saying air tight houses while another says ventilation needed. I know you could say heat recovery system allows for ventilation while not losing expensive heat, but I am always dubious about anything that requires mechanisation (I know we have lots of it and can't do without it) and prefer systems that are designed to operate without intervention.

Air tight with heat recovery on ventilation works for me. You can always open the door for a bit if the heat recovery fan stops working, but not so easy to plug all the little gaps when the heater stops/ planet runs out of oil.

 

[Exfarmer]

We live in a very highly insulated house and the result is we need the windows wide open most of the year, in fact we are seriously looking at installing air con. I would give anything to go back to a draughty old farmhouse , but my wife won't move