Ground Source Heat Pumps

[burton]

As the first cold days arrive, we’re experiencing the reality of trying to keep our new house warm. It’s both difficult and expensive. We’ve pretty much written off any solution other than buying extra jumpers for this winter, and our children will have the happy experience of waking up with frost on the inside of their windows. One year of this will be enough, so I’m looking round at heating options and ground source heat pumps look appealing.

Has anyone on here got one or had experience of installing them? I realise the initial investment is high, but the current subsidy looks appealing and could offer full payback on install costs over the seven years and a significant contribution toward running costs. Price is an issue for us, but we are expecting a small windfall which would just about cover the initial outlay.

Relevant facts

House is Victorian with thick stone walls. Rooms are big, with high (3.5m) ceilings, there’s 3 bedrooms, a dining room, living room, office, kitchen and utility
Loft has been well insulated
We’re installing secondary glazing throughout
It’s grade 2 listed, so our freedom to add insulation is restricted
Garden has about 400m2 of lawn, so hopefully we wouldn’t need to put in boreholes for the heating loops
No mains gas is available
Our current heating is a couple of log burners in downstairs rooms. Everywhere else is cheap (to buy, not run) electric heaters. Yet to carry out a full test, but I reckon that having them switched on enough of the time to keep the house warm would cost about £60/day. Buying jumpers seems like a better use of money.
I realise underfloor heating would be the ideal solution, but realistically it’s more likely we would end up using the heat pumps to drive radiators

Any comments?

[FUZZY]

Simple stuff like thick curtains, draft excluders and substantial underlay can make a big difference. If you can manage it, move the radiators from the usual, maximum inefficiency position beneath the windows to internal walls where a substantial portion of the heat generated won’t be immediately leeched outside.

[jaz]

What about oil fired central heating with conventional radiators?

[burton]

That’s probably the other realistic option. Lower initial cost, and it would mean we didn’t need to dig up the whole garden. At this stage I’d prefer a heat pump for 2 reasons

1. It’s more environmentally friendly

2. Installation costs are likely to work out way cheaper in the long run thanks to the RHI subsidy.

[dave]

They rely on pushing out a low but consistent temp. So aren’t suited to poorly insulated houses and existing radiator systems that require water temps of 50 or 60 degrees.

[guy]

With a solid walled place like yours (and mine), the heat losses will be such that the radiators would need to be hot in order to provide sufficient heat. This means that the COP (roughly: heat out/electricity in) of your heat pumps will be close to 1. That means you will be paying electricity prices for each unit of heat. That means it would be a very expensive way of heating your house, even if the installation costs were zero.

[burton]

Thanks, I hadn’t realised that a higher output temperature dropped the efficiency of the pump. At a COP of 1, presumably running costs would be similar to our existing electric heaters.

If we accepted that the purpose of the heaters was to stop the house being cold, rather than actually making it warm, presumably we could push up the COP? I feel like one advantage of the thick stone walls is that if we can keep some heat in them, they act like storage heaters, albeit ones which put a decent chunk of their heat out into the garden.

[jyn]

Sorry to not answe your question, but…

Grade II listing shouldn’t restrict you to badly. You should be able to make changes so long as they don’t damage the features behind the listing.

We didn’t want to touch some of our inside walls – to preserve damp proofing, and outside insulation is limited by conservation area status. So we threw stud partition walls up inside the real walls and insulated those. An added bonus of this is that doing a rewrite is much simpler by running stuff in the fake walls.

If you think that’s viable, take a proposal to your local listed buildings officer. Invest some effort in getting them on side.

GSHP – it’s a hell of a big dig for a shallow system.

In winter we heat a lot of our house with a 10 kw log burner and convection currents of air – but I have 60 mature leylandii trees to dispose of…

Someone – LG I think – do a high temperature air source heat pump that works with normal sized radiators. My 5 year plan is to fit a high temperature ASHP, thermal store and external log burning boiler to our garage and to get rid of the oil boiler.

[burton]

We didn’t want to touch our walls inside to preserve damp proofing, and outside is limited by conservation area. So we threw stud partition walls up inside the real walls and insulated those. Added bonus is doing a rewrite is much simpler running stuff in the fake walls.

This is a good idea, and the route we’ve gone down in both our old house and the annex in the new one. Could be an option in the main part of the house, biggest problem would be that the window reveals are already deep and this would make them even deeper. Nearly all the external walls have windows in them.

If you think that’s viable, take a proposal to your local listed buildings officer. Invest some effort in getting them on side.

Our local listed building team seem very reasonable. I’ve already got a conversation going with them, can’t complain about any of their decisions up until now.

GSHP – it’s a hell of a big dig for a shallow system.

Think it would mean digging up pretty much the whole garden. While it’s not appealing, the kids love diggers and we could put turf back down to get it usable again quickly.

In winter we heat a lot of our house with a 10 kw log burner and convection currents of air – but I have 60 mature leylandii trees to dispose of…

Someone – LG I think – do a high temperature air source heat pump that works with normal sized radiators. My 5 year plan is to fit a high temperature ASHP, thermal store and external log burning boiler to our garage and get rid of the oil boiler.

This is the kind of imaginative solution I would like for our house. Adding oil fired central heating is the obvious solution, but seems a bit retrograde

[jyn]

biggest problem would be that the window reveals are already deep and this would make them even deeper.

That’s exactly our situation. It makes it awkward to open/close them but the extra-deep window sills are a great place to put Stuff. We used plywood for the sills in the end – gives a nice look.

This is the kind of imaginative solution I would like for our house. Adding oil fired central heating is the obvious solution, but seems a bit retrograde

We fitted oil in 2015 – ran out of money after unexpectedly having to replace all the first floor joists and had to move in. It’s a good boiler but it’s big, noisy, the exhaust stinks and it’s decidedly not the way of the future.

A high temperature ASHP should be able to take its place, albeit running about 2.5x as long per day as the boiler. We still have glazing and insulation improvements to do however. My ill defined plan is to plumb an outside log burner in to a second coil (what is typically solar thermal input) on the thermal store. I’d start with a cheap, simple unit and see how it goes. Or perhaps something like this inside the garage – http://www.ludlowstoves.co.uk/product/klover-utility-boiler

One thing I wouldn’t consider if you are over 50 is a wood chip burner. Their hoppers need filling every few days with heavy bags of biomass. If you get one aged 50 and are tied to it for 20 years by the RHI, you’ll be lifting bags weekly aged 70 – and more frequently in the coldest, most horrid weather. I sometimes wonder how many retirees are going to get bitten by this.

[Neil W]

One thing I wouldn’t consider if you are over 50 is a wood chip burner. Their hoppers need filling every few days with heavy bags of biomass. If you get one aged 50 and are tied to it for 20 years by the RHI, you’ll be lifting bags weekly aged 70 – and more frequently in the coldest, most horrid weather. I sometimes wonder how many retirees are going to get bitten by this.

I’ve got one of these (well, compressed sawdust pellets) in a poorly insulated large house in the Alps – but I’m 43 and fit (I had to carry 600x15kg bags of pellets into the house to store when they got delivered last month!). It’s meant to be temporary however.

However, if you have the space, you can get large silos to automatically feed the boiler. My neighbour has one and the silo takes up barely more space than oil tanks. Rather than sacks, a large truck turns up and spurts pellets into the silo via a hose once or twice a year.

[housemouse]

Have you considered air source heat pumps.

Mitsubishi are claiming to have a new range of co2 refrigerant based ones offering CoPs of up to 4 whilst producing DHW.

They sound too good to be true and they might be. I’ve not checked to deeply yet.

https://www.ecodan.de/en/heat-pumps/co2-hot-water-heat-pumps/

[burton]

Have considered them, and happy to continue to. Marks against them are being visually obtrusive and lower efficiencies in winter due to colder ambient temperature.

[housemouse]

If their seasonal CoP is to be believed they seem really impressive. Can you install underfloor heating. If you have underfloor you can normally have a lower flow and return temp and thus a higher COP.

What is the DHW provided by?

I think there might be noise issues as well from the condenser.

[keith]

I have ASHP – get some proper advice. You need an up to date energy cert, and then ideally a thermal model of the house (our installer did all this) to size the rads and the ASHP. Ours is paying for itself in no time thanks to RHI and saving vs oil.

[nab]

If the listing of the building allows I would certainly look at some good insulation on the insides of the external walls.

As you say it will make the window reveals even larger and there might be room features (eg coving) that would make it hard to achieve but I think it would make a big difference. Something like 100mm Kingspan or to be more environmentally friendly sheep wool.

[Kez]

In the short term if you have a tent you could put it up in the children’s room over the coldest weeks. Gives them some cosy space. Or bunk beds with curtains.

I’ve no idea about efficency, but all the people I’ve met who live in houses like that have an aga or similar and mostly live in the kitchen in the winter rather than trying to heat the entire house.

As mentioned above curtains are important, over doors as well as windows.

[oldfogie]

My only experience of ground source is through neighbours who installed one in their stone, un-insulated farm worker’s cottage. They had to dig two huge trenches in the paddock, they regretted placing the pump in the utility room because the throbbing keeps them awake, they had to dig up all the floors and lay insulation then the pipework then screed. They had to dry-line all exterior walls and they fitted shutters inside all the windows. The house is warm but because they blocked all ventilation it always smells stale and feels humid inside; if they still had cold walls they would be suffering a lot of condensation. I can see how it would work in a properly insulated building but as a retro-fit it doesn’t suit the house very well.

Does listing allow you to insulate all the exterior walls and upstairs ceilings? This is relatively cheap and brings enormous benefits; we insulated our son’s cold bedroom with 3 exterior walls and now the heat from the fan on his computer is enough to keep him warm when he’s hammering it playing GTA. The room is much quieter and very cosy and a really pleasant place to be.

[Phil]

I live in a similar house. I think it is worth considering whether attempting to heat large, stone Victorian houses is sensible at all . Personally I think aiming to heat the whole place is either unrealistic cost-wise, or requires destroying the period interior (which I like) and possibly exterior for GSHP. It is however fairly easy to stay comfortable by more jumpers, blankets on sofas, thick duvets etc. together with heating in key rooms and closing doors. My heat+light bill is <£60/month and it is not miserable.

[burton]

There’s something in this, and we bought the house knowing it would be hard to heat. At present, we have a room we can retreat to and get warm with a log burner, and at a basic level that’s all we need. Bedrooms are chilly, but actually that’s fine as long as you have a decent duvet.

Have spoken to a local renewable energy consultancy/installer to see what they think. If they promise me a warm house and low bills, I’ll be very dubious. If they can come up with a solution that keeps the house warm enough that I don’t need a down jacket, and the figures stack up, then I’ll be interested.

Thanks for all the responses above, flagged up a few things I hadn’t considered before.

[pakpak]

Heat pumps work best with / can only provide a low output temperature (50degrees max?). There’s no reason why you can’t use them with radiators, you just need bigger radiators to compensate for the lower temperature they’re running at. If you have the wallspace and the listing allows, then this may be the way forward. Same goes for condenser boilers, there’s a step improvement in efficiency by running them below a certain temperature. We’ve recently replaced our rads in a solid Victorian house like yours and did just that – We used the online calculator on theradiatorcompany.co.uk with ‘worst case’ options set as our minimum size requirements. It’s also more efficient to run any heating system if the return water has lost all it’s heat – heat transfer is more efficient in the ‘boiler’ when the difference in temp is higher. Bigger rads = more chance for the water to lose it’s heat. Underfloor heating is normally used because it’s simply a massive radiator. The problem you may have with UF heating is if you have suspended timber ground floors – you then have to work out how to insulate underneath to stop the heat being sucked out the void by the wind. If you have suspended floors and are thinking of replacing them with concrete ones to facilitate UF heating…don’t – you’ll give yourself ‘rising’ damp problems.

I think it’s foolish to consider anything other than heat pumps for a ‘new’ install like this if you can afford the capital expenditure, have the physical ability to install at sensible cost, and anticipate being in the house for a long time – you’re only storing up problems for yourself when fossil fuels become restricted or expensive. Heat pumps also run on electricity which is increasingly becoming sourced from renewables.

If you do go for UF heating it’s best used to provide for ‘baseload’ because it takes so long to heat up and cool down. You still need a means of providing ‘boost’ heating (stoves / fires / electric heaters).

Word of warning – I know of someone who froze their garden and killed everything growing in it by badly speccing their heatpump setup and sucking all the heat out of it. Extra pipe and digging is relatively cheap.

[Sammyf]

Have you thought about getting a burner with a back boiler? After all you’re already burning wood to keep the place warm, might as well make the most out of it…

We have a large 24kw (or something!) burner with a back boiler that heaters up a thermal store. The thermal store provides hot water at a temperature suitable for radiators (the bedrooms) and is mixed down to a cooler temp for underfloor heating.

The thermal store also gets heated by excess PV so over the summer when we don’t have the burner in we can still get hot water.

We thought about ground source heating but we’re on a clay soil and it wasn’t suitable (as I understand it you need soil porous enough for decent water flow as that’s what replenished heat to your pipes).

I re-iterate what everyone else about insulation, seal up as much as you are able, it makes loads of difference!

We spent 18 months in a freezing static with portable electric heaters, I feel your pain.

[guy]

Are you sure about the £60 / day for the electric heaters? Running 5 2000 watt electric heater 24 hours per day at 14p per kWh comes to £33.60 per day. (Be careful running 5 x 2000watts appliance – it could overload the ring main)

bottled lpg is worth considering with a gas boiler and radiator system.

I live in a 3 bedroom listed building and have been using bottles lpg for the last 5 or so years and it is reasonable on running costs.

Someone mentioned in the posts above, to insulate the inside of the outside walls – be careful doing this, it can lead to overheating in the summer and you will lose the benefit of the large thermal mass that thick walls gives for both summer and winter.

3.5m ceiling heights might make ceiling fans a viable option to push the heat down