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

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

Joined: 28 Oct 2004
Posts: 45674
Location: Essex

Posted: Thu Feb 18, 21 10:41 am Post subject:

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: 15993

Posted: Thu Feb 18, 21 4:40 pm Post subject:

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: 6612
Location: New England (In the US of A)

Posted: Thu Feb 18, 21 5:04 pm Post subject:

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: 45674
Location: Essex

Posted: Thu Feb 18, 21 6:28 pm Post subject:
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: 6612
Location: New England (In the US of A)

Posted: Thu Feb 18, 21 8:53 pm Post subject:
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: 15993

Posted: Fri Feb 19, 21 8:24 am Post subject:
Do you just have one Slim, and if so, which room does it vent into?

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Feb 19, 21 11:20 am Post subject:

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

Posted: Fri Feb 19, 21 5:32 pm Post subject:

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!

dpack

Joined: 02 Jul 2005
Posts: 46244
Location: yes

Posted: Fri Feb 19, 21 5:57 pm Post subject:
underfloor heating is tricky even in new build to do it where you need to dig out, insulate, secure pipe and pour is a lot of expensive work

tahir

Joined: 28 Oct 2004
Posts: 45674
Location: Essex

Posted: Fri Feb 19, 21 6:07 pm Post subject:

dpack wrote:

underfloor heating is tricky even in new build

It's not, as long as you know what you're doing. Also roobarb is going with rads.

It definitely needs careful evaluation, it's going to cost a lump so it needs to be specified correctly.

dpack

Joined: 02 Jul 2005
Posts: 46244
Location: yes

Posted: Fri Feb 19, 21 6:59 pm Post subject:
the outside energy collection side seems fairly easy, tis the how to use the heat that seems tricky rads using preheated water seems plausible

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Fri Feb 19, 21 7:23 pm Post subject:
Tahir,How much electricity do these ground and air source heat pumps need to run on if one does`nt have ones own solar panels? I was once told by a rep trying to get me interested in an air source heat pump a figure twice what my electricity bill was.

tahir

Joined: 28 Oct 2004
Posts: 45674
Location: Essex

Posted: Fri Feb 19, 21 8:41 pm Post subject:
I’ve got a gas boiler (calor) my brother has ASHP both our houses are passivhaus standard. His is a bit bigger than mine we spend about the same on heating The big issue with them is that you really need a decent level of insulation to avoid huge peak demand

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Feb 19, 21 9:54 pm Post subject:

What are the coldest temperatures like? I would suspect that they're not so cold that an air source heat pump won't be able to handle 95% of the heating needs. That could be where the wood stove comes in, with it's reduced role.
I would at least get a competitive quote, as I expect the cost of ground source would be more upfront than I would be interested in paying for what I imagine being not too much better performance than air source.

I know you're looking at air to water, but our air to air was less than $3k installed.

Mistress Rose

Joined: 21 Jul 2011
Posts: 15993

Posted: Sat Feb 20, 21 8:07 am Post subject:

I'm not going to criticise your decision Roobarb; that is up to you, but I have a feeling, perhaps ill founded, that particulates are the 'in thing' at the moment as we haven't been able to trace them in the human body until recently. We have also been living with fire for thousands of years, apparently with few ill effects. I would also point out that there are fewer particulates given off if a fire is going constantly than if the chimney gets cold and is used less frequently.

Slim, I am sure our winter temperatures are nothing like as low as yours, but ours is a damp cold. At present the night temperature here is about 5 deg C, so not cold at all by your standards, but it is damp if not raining, and with some wind chill.

We tend to heat our house in the same way. We have the fire going all the time, low during the day when we are not there, and no central heating, but all the doors are open, so any hot air goes round the house. At night, unless it is very cold, we shut the bedroom door to keep the room cooler. The central heating thermostat is in the study with various computer bits running, so it tends to be more of a secondary heating in some ways as it is set fairly low and in a room heated to some extent.

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