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Ground Source Heat Pumps...are they worth it?
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roobarb



Joined: 15 Apr 2008
Posts: 139
Location: Carmarthenshire
PostPosted: Wed Feb 17, 21 3:44 pm    Post subject: Ground Source Heat Pumps...are they worth it? Reply with quote
    

We are considering replacing our current heating system (log burner with back boiler, with us sourcing the wood ourselves, so costs are minimal, but time input high) with a ground source heat pump. The reasons being that as we get older we are wanting a more automated system, less hands on than our current wood burning system, and there is also growing concern about the health of burning wood in the home.

Have any Downsizers gone down the GSHP route, and how have you found it? They are damn expensive to install (even with the RHI...no green home grants in Wales), but we're promised that the cost of running it will not be any more, and more likely less than being on oil or having to buy in wood, but how true is that? Are they as efficient as the installers and manufacturers claim, or are we going to be faced with a huge electricity bill to keep the house even vaguely warm? We've read horror stories about ASHPs, but very little is written about GSHPs perhaps because they aren't as common.

We have also been considering a pellet boiler, which has the appeal of being automated, but we then become reliant on buying in fuel, with an unknown future costs attached.

Our house is 3 beds, stone built cottage but with external insulation, in West Wales, all of which we know make a difference to any other persons experience/costs of running a GSHP.

All thoughts on the topic gratfully recieved.

tahir



Joined: 28 Oct 2004
Posts: 44788
Location: Essex
PostPosted: Wed Feb 17, 21 4:34 pm    Post subject: Reply with quote
    

Most pelleted fuel is imported, or from imported timber so a no from me on that.

GSHP and ASHP are both good if specified correctly. Ideally they want to be running an underfloor heating system with a flow temperature of around 27c.

What would you be looking at in terms of heating?

Obviously the best money you can spend is on reducing demand; insulation and getting rid of any draft sources (airbricks etc), double glazing and so on.

We've used ASHP on two sites and they can be noisy if they're overworked, we're currently looking at GSHP for a block of 9 flats.

Let me know a bit more and I'll help as best I can.

roobarb



Joined: 15 Apr 2008
Posts: 139
Location: Carmarthenshire
PostPosted: Wed Feb 17, 21 5:16 pm    Post subject: Reply with quote
    

Agree with you on the pellets, and sources being variable, especially as part of the reason for going down this route is to be as sustainable as possible.

We know that underfloor heating is best for heat pumps, but given the right size radiators, these can work as well, so this is what we'll be looking at, with a number of radiators needing to be replaced so they are over-sized.

Hot water heating will also need to be considered, but we have solar thermal for the summer months, so the heat pump will only be required for this from October - April.

We have been told our house requires c. 20,000kWH, and the first quote we've had is for a 12kwh system.

We've pretty much ticked all boxes we can on getting the house up to good spec...double glazing throughout, external wall insulation (we're solid wall), although we could do with topping up loft insulation.

tahir



Joined: 28 Oct 2004
Posts: 44788
Location: Essex
PostPosted: Wed Feb 17, 21 5:41 pm    Post subject: Reply with quote
    

Do you have airbricks? Or extract fans?

Mistress Rose



Joined: 21 Jul 2011
Posts: 12843

PostPosted: Thu Feb 18, 21 9:24 am    Post subject: Reply with quote
    

One thing to be aware of if you are sealing your house is air management. If you seal it, you have the problem of condensation and potential mould. This often seems to be forgotten.

Sorry, no information on GSHP, but agree with Tahir about pellets. The best way to use wood is by using logs as there is less processing and you should be able, as you have been, to get it local. Is there any way you can improve your effectiveness in wood cutting and preparation. Because we do something like 100cu m a year, as well as cutting for charcoal production, we have invested in equipment, which does use fossil fuel, but is still probably better in that direction than most heating systems.

Slim uses an ASHP, and uses wood as a 'top up'. Keeping the wherewithal to have a top up with wood is something I would suggest.

dpack



Joined: 02 Jul 2005
Posts: 39851
Location: yes
PostPosted: Thu Feb 18, 21 10:16 am    Post subject: Reply with quote
    

do you have major floor works planned anyway?
if not gshp is a lot of mess for a small very long term return

are you likely to live there for at least the next 30 years?
see long term

how big an area do you have for energy harvest?
what is it made of?
do you have a stream?

retro fit is never as good as designed into new build, but it can be done

the house was built around working fireplaces and chimneys, using them is part of keeping it dry and cosy and ventilated
even with "modern"energy sources dry and ventilated needs taking into account

to get the best from gshp i would go for new build and a working life of 50 yrs(new pumps etc as required but the basic pipes etc need to be long lasting and zero maintenance)

personally i would not touch retrofit gshp with a very long bit of pipe

dpack



Joined: 02 Jul 2005
Posts: 39851
Location: yes
PostPosted: Thu Feb 18, 21 10:19 am    Post subject: Reply with quote
    

delete "even with" and insert "especially with"

tahir



Joined: 28 Oct 2004
Posts: 44788
Location: Essex
PostPosted: Thu Feb 18, 21 10:41 am    Post subject: Reply with quote
    

Mistress Rose wrote:
One thing to be aware of if you are sealing your house is air management. If you seal it, you have the problem of condensation and potential mould. This often seems to be forgotten.


Absolutely, we're building to Passivhaus standard nowadays, extremely airtight so air management is crucial. However replacing uncontrolled fans/airbricks with dmevs is very useful:

https://www.greenwood.co.uk/continuous-extract/-dmev

I'd recommend these to anyone

Mistress Rose



Joined: 21 Jul 2011
Posts: 12843

PostPosted: Thu Feb 18, 21 4:40 pm    Post subject: Reply with quote
    

I thought you would have been aware of that Tahir, but I get the impression that particularly retro-fit doesn't take it into account, and to my mind it is more important than sealing the house.

While I agree about uncontrolled draughts, I was brought up with air bricks, and although the house was cold as no central heating, the major problem I had with them was the big spiders that came from the cavity wall. I don't mind spiders, although I am not fond of them, but a large one emerging from an air brick is rather upsetting in half light.

Slim



Joined: 05 Mar 2006
Posts: 5993
Location: New England (In the US of A)
PostPosted: Thu Feb 18, 21 5:04 pm    Post subject: Reply with quote
    

Mistress Rose wrote:

Slim uses an ASHP, and uses wood as a 'top up'. Keeping the wherewithal to have a top up with wood is something I would suggest.


Other way around actually. We burn about 4 cords a year, and replacing that with just heat pump would mean needing to increase our solar panels! (Net metered power, so we're drawing down our credits from summer energy production - though that's true with our firewood too!)

Our air to air heat pump is great for the days when there is some chill but the stove would make us too hot, or when the sun will be warming things soon anyway. Also nice for it to kick on in the morning when you don't want to jump up and restart the fire first thing (especially with babes in the house, we don't tend to let it get as cold as we likely will in the future).

Our heat pump does fine too hear by itself, like when we leave town for a bit, but I also make sure our propane heater is on in the coldest weather, so it will kick in if the heat pump isn't keeping up (10 F and below the heat pump is still functional but not as impactful - that's where ground source would be able to keep chugging along because the temperature differential doesn't get as drastic as our winter air)

Air to air heat pump was pretty darn fast and cheap to have installed.

tahir



Joined: 28 Oct 2004
Posts: 44788
Location: Essex
PostPosted: Thu Feb 18, 21 6:28 pm    Post subject: Reply with quote
    

I think there are air to air heat pumps around in the UK but it's mostly air to water like these

Slim



Joined: 05 Mar 2006
Posts: 5993
Location: New England (In the US of A)
PostPosted: Thu Feb 18, 21 8:53 pm    Post subject: Reply with quote
    

I got a fujitsu, looks like they're around your way as well: https://www.fujitsu-general.com/uk/products/split/index.html

Mistress Rose



Joined: 21 Jul 2011
Posts: 12843

PostPosted: Fri Feb 19, 21 8:24 am    Post subject: Reply with quote
    

Do you just have one Slim, and if so, which room does it vent into?

Slim



Joined: 05 Mar 2006
Posts: 5993
Location: New England (In the US of A)
PostPosted: Fri Feb 19, 21 11:20 am    Post subject: Reply with quote
    

We have a simple setup. When we moved in the baseboard radiators were not functional, so I removed them, knowing we weren't likely to get a new boiler and re-plumb them. The only heat was the propane fueled Rinnai (wall vented) in the living room (southwest corner). We put our wood cookstove in the dining room (southeast corner) toward the center of the house. The heat pump head went into the dining room as well, on the eastern wall near the corner with the southern wall. Because the heat pump always moves some air to measure temperature, it helps add to the circulation of heated air around the house.
Most frequently:
Woodstove produces most of the heat in the dining room, which circles around (and up) the staircase in the center of the house, into the living room, into the back hallway and the bedroom and bathroom that come off of that, and then into the kitchen which opens out into the dining room again (with a big enough doorway that it probably has it's own circulation of air exchange with the dining room as well, always plenty warm.)
The upstairs was unfinished when we moved in, and we decided not to put any heating in up there. We've finished about half of it so far, and these bedrooms are plenty warm when the doors are open, and chillier when you keep the doors closed, so you set your temperature that way, essentially.
Because the heat pump is in the same room as the stove, we keep it's thermostat up higher than we would set it if we weren't using the stove, to make sure it starts working before the stove has fully cooled down when we wake up (and the rest of the house is feeling cold). On very cold nights the propane heater comes on as well - though my long term plan is to replace that with something not fossil fueled, like an electric resistance heater. I E., wood heat with all electric supplement, but higher efficiency heat pump as the primary supplement, with less efficient resistance heater for only the coldest times when the heat pump struggles.
Full plan is to eventually switch vehicles to electric and put another set of solar panels on the roof to cover vehicles and any new electric demand from a resistance heater.

roobarb



Joined: 15 Apr 2008
Posts: 139
Location: Carmarthenshire
PostPosted: Fri Feb 19, 21 5:32 pm    Post subject: Reply with quote
    

Thanks for replies.
Quote:
Do you have airbricks? Or extract fans?


No air bricks or extractor fans..we invested in a woodburner with an external air source, so we didn't have to install any air bricks, and we open windows after showers and in the kitchen if we're producing steam! We use a dehumidifier quite a lot if we feel humidity is becoming a problem.

We have a largish field next to the house, which we have ear-marked for the pipework for the GSHP. It's very rough pasture so we're not bothered if it gets turned over.

No plans to re-do the floors, so it will have to be radiators.
We're planning on being here for some time, at least for the next 15-20 years, so the investment will be for us, and not for some future owner of the house.

We would keep at least our smaller woodburner, which heats the living room, but as I said in the initial post one of the reasons for going down this route is to start limiting the use of wood burning in the home. This will perhaps open up a can of worms on this forum, but there has been quite a lot of recent research showing the health hazards of particulates from using a woodburner in the home (not just the particulates going up the chimney and into the atmosphere, which is another issue that is perhaps more of a concern in urban areas).

Quote:
personally i would not touch retrofit gshp with a very long bit of pipe
Have you had experience of this, or is it just a gut feeling!

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