Air source Heat Pumps any good?

[Spectric]

We do need to stop building outdated shiete housing just so the property developers can get a bigger yacht and maintain there OTT lifesyles at the expense of the majority of uk home owners. Housing is an essential need and the building regs need to be updated so that houses are built to meet future needs with less energy consumption, Ie properly insulated and have much thicker walls so they can be warm in winter and not overly hot in summer but this needs to happen during the build and not as a retrofit.

 

[Terry - Somerset]

It is tempting to focus on one aspect of domestic energy use at the expense of the rest. One analysis for the UK shows space heating 61%, water heating 23%, lighting and appliance 13%, cooking 3%. For the latter two there is little alternative to electricity (+gas for cooking).

Insulation is a distraction - better insulation = lower energy costs or lower investment costs irrespective of how the energy is used.

A few folk have the good fortune to have space for GSHP or woodland. Few have a personal coal mine or oil well. This is not some sort of generic solution for society generally - the potential output in the UK would not come close to meeting potential demand.

For space heating, a split AC unit has the capacity to generate both heat and cooling at a coefficient of performance of 3.0-4.0. Commonplace in Europe, performance, close to ground and air source heat pumps. Capital costs less + no need for radiators, underfloor pipework etc.

Water heating can be solar, gas or electric. There may be a balance between size of storage tanks and reliability of usable output. The real question is where the electricity is generated to boost hot water supply and run a split AC.

PVs only generate power during daylight hours - batteries or mains connection needed at other times. There is a complex financial and practical balance between the size and costs of PV installation, size of battery back up, excess power generated sold to grid (likely in summer).

There is no "one size fits all"

 

[Phil Pascoe]

Can't say about your jurisdictions but many of the Canadian cities have banned wood burning fireplaces, wood stoves etc because of the smoke particle pollution and even fire pits in the backyard are only allowed if permits are taken and nobody complains. Then there are the insurance companies that will either outright refuse to insure or have extortionist rates for any kind of wood heat in the workshop. They don't make it easy to heat inexpensively.

Pete

Serve you right for living in Canada.

 

[Nic Rhodes]

we have had a suggestion to put PV on the pool which I have resisted. I pointed out to them all we need to do is heat water to 25 degrees so why not just heat water with sun? There seems a desire to throw tech at problems when it is not the solution.

 

[D_W]

As a (now ex) electrician I have been involved in projects involving Air source (Air to water) heat pumps to provide space and water heating.

I may have given some information that's mistaken if I understand correctly that air to water is common there. Here in the states, it's air to air or ground to air. There may be retrofit ground to water heat pumps, but I've never seen them.

It's far more common here to have ducting installed and radiators or baseboards mothballed because the update kills two birds with one stone - getting away from oil and getting whole house air conditioning in place.

 

[D_W]

we have had a suggestion to put PV on the pool which I have resisted. I pointed out to them all we need to do is heat water to 25 degrees so why not just heat water with sun? There seems a desire to throw tech at problems when it is not the solution.

are there not solar covers there? They used to be the norm here, but i haven't seen them in a long time - maybe that was a 90s thing. You could pretty much get a pool warm enough that if someone peed on you in it, you couldn't tell the temperature difference. Just with solar heating through the cover. maybe people thought rolling out the cover was inconvenient. High temp also created the need for more water treatment to prevent pool water from turning green.

PV sounds more convenient but not very efficient given a pool is a giant transfer of energy if the water in it is warmer than what's around it.

 

[mikej460]

We live in the sticks with no gas and moved here in 2007, inheriting an 18 year old oil boiler which was subsequently condemned by the local heating engineer. After much research we bought a condensing log boiler, solar thermal panels and thermal store. It worked but I learned some painful lessons:
1. You need a lot of very dry logs for the system to operate efficiently. Most people buy a maximum of one bulk bag of logs a month for their wood burners whereas we needed one a week.
2. At the time log men ran out of dry logs in January around here (this has improved lately as two businesses have setup offering kiln dried logs). Damp logs produce far less heat and far too much pollution.
3. These boilers need stoking several times a day in mid-winter which is a real stress if you are away at work
4. Stacking and loading logs is hard work
5. Solar Thermal works incredibly well but can easily over heat in summer so you need some form of heat dump.

I gave up after 3 years of constant stress and sold the system, replacing it with the current wood pellet system, and order was restored. We did buy a Solar Megaflow HW tank and when we have our roof replaced we will have a smaller solar thermal system installed for HW.

However, with the benefit of hindsight with more time to manage it, coupled with the knowledge, land and time to make and use a solar kiln to kiln dry logs and store them, I have this weird yearning to revert to a log boiler - but it might be a sign of impending madness and acceptable grounds for divorce.....

 

[Dee J]

I may have given some information that's mistaken if I understand correctly that air to water is common there. Here in the states, it's air to air or ground to air. There may be retrofit ground to water heat pumps, but I've never seen them.

It's far more common here to have ducting installed and radiators or baseboards mothballed because the update kills two birds with one stone - getting away from oil and getting whole house air conditioning in place.

In my area - rural South-West UK any sort of heat pump technology is a new and rare thing. The UK has no tradition of (or until recently, need of) domestic air conditioning (cooling). The new convention, as I've seen it, is air to water with an integrated system of heating and hot water - involving multi-zone wet under-floor heating combined with a thermal store and buffer tank. Multiple stats, multiple pumps, computer control, automatic timed legionella boost on hot water, use of electrical heating to defrost the external unit in cold weather. Cost typically £20k. High running costs and high maintenance costs only made viable by government subsidies. Doesn't seem a viable option for most houses. Hence my own preferences.

 

[D_W]

If you guys are bored, you can look up the "GARN WHS" on YT here. It was a hot water circulating system that was housed in a separate building and instead of burning a slow fire all the time, it burned an intense fire for a fraction of a day every other day and heated a big store of water. When the water temperature drops below a certain level, you put more wood in and it pretty much burns smoke free and very hot.

Great idea, but I'm sure it would be $30k now and it needs to be in a separate building.

One of the things that motivated my dad to stop burning wood was the amount of work with wood compared to just paying for oil.. Just moving around 9 cords of wood a year even if someone else delivers it is a big pain. Carry it into the house and bugs wake up, so you end up only carrying in when it's ready to go in the stove, which meant for us having a small secondary stack to go into the stove. So we ended up moving the wood one more time from the pile to a 1/4 cord rack under an overhang.

it was nice to have a hot spot if you were outside in the winter or woke up and the upstairs was cold - my parents often didn't heat the upstairs overnight, so in the winter, it *was* cold. Heat was off from 11pm -5:30am.

 

[D_W]

In my area - rural South-West UK any sort of heat pump technology is a new and rare thing. The UK has no tradition of (or until recently, need of) domestic air conditioning (cooling). The new convention, as I've seen it, is air to water with an integrated system of heating and hot water - involving multi-zone wet under-floor heating combined with a thermal store and buffer tank. Multiple stats, multiple pumps, computer control, automatic timed legionella boost on hot water, use of electrical heating to defrost the external unit in cold weather. Cost typically £20k. High running costs and high maintenance costs only made viable by government subsidies. Doesn't seem a viable option for most houses. Hence my own preferences.

Using air to heat water sounds like a terrible idea. If water heating is needed, the GSHPs here do have some kind of heat pump type water heating, but they're slows. Brother in law mentioned that it takes hours for an 80 gallon tank to recover (many hours) on the high efficiency heater type, but instead of going back to a regular electric water heater, he added another 80 gallon tank that circulates with the main tank.

My parents believed that only "stable heat" was good heat when I was a kid. Either constant woodburning or baseboard and water only - anything else is too much up and down according to them.

When I moved to the suburbs, I moved into a house that has ducting - on the very coldest days you may notice a slight variation, but there is no making temp changes and then noticing an overshot or anything like that, or waiting and waiting.

And almost no dust thanks to the gradual filtering of all of the air - even with the cheapest fiber filters in the furnace, almost no dust.

As a kid, dust was absolutely constant settling everywhere.

 

[Chris70]

Well, look, I haven’t read all the above but I get the gist of it. Most aren’t keen, considering the financial aspect. That said, we must stop killing this planet with fossil fuels!

When you buy a house they say “Location, location, location!” When you buy a Heat Pump I’d say, “Insulation, insulation, insulation!”

As others before me have said, UFH goes ‘hand in glove’ with an ASHP.

We’ve just had a Mitsubishi ’Ecodan’ 11kW ASHP installed (6 months ago) when the RHI was slightly better, ie, not a £5k one-off. We did a major refurb/extend. Roof off, suspended floors replaced with solid floor UFH, new uPVC DG windows and so on.

Every Wednesday at 03:00 our regular Setpoint of 53C is elevated (for a couple of hours?) to combat Legionella.

We’re not millionaires, but we are able to do our ‘green bit’. Even if it doesn’t make sense financially, doesn’t it makes sense ecologically? And with the fuel price hikes we’ve had, and further hikes we will likely see, we’re thinking we’ve made the right decision.

We also think GSHPs are better than ASHPs, but they’re more expensive to install plus you need a certain amount of land which we don’t have.

I reckon I’ve covered most points.

Chris

 

[Jacob]

.........

When you buy a house they say “Location, location, location!” When you buy a Heat Pump I’d say, “Insulation, insulation, insulation!”

And if you don't buy a heat pump say “Insulation, insulation, insulation!” even louder!
Can't say I'm very interested in heat pumps et al as they are expensive and fairly high tech, which means they aren't accessible to 99% of the population and are vulnerable to tech failure.
Insulation is neither of these.

 

[deema]

Insulation and solid walls particularly those made of brick and lime cement don’t mix I understand. The walls need to breath and anything that restricts it causes damp which is very unpleasant!
Again solid floors without insulation or a damp proof course are also impossible to insulate if linked to solid walls. Listed buildings are also a nightmare and with restrictions make it almost impossible to insulate. So it’s either freeze, or pay a fortune to heat them. Going forward something has to give or else all our historic buildings will become empty and unsaleable.

Rentals have to be EPC band D rising to C in the next few years. A lot of housing stock will never get there. They are looking to restrict / give less favourable terms for mortgages with poor EPC which again will make these houses less desirable.

For me personally, economics and saving the planet must go hand in glove. If ASHP or GSHP do not financially make sense at the moment I will wait until they do / the next technology comes along.

I admire Sideways investing in solar, but the price / return makes no sense to me at all. A payback it circa 15 years is not a viable ‘business’ proposition. Payback needs to be less than five years for it to make financial logic.

 

[Jacob]

.Insulation and solid walls particularly those made of brick and lime cement don’t mix I understand. The walls need to breath and anything that restricts it causes damp which is very unpleasant!

Depends on the details but generally not a problem.

..... Listed buildings are also a nightmare and with restrictions make it almost impossible to insulate. .....

We insulated our chapel conversion with stud linings plus 100mm Kingspan to all the external walls , with 50mm in window reveals and 250mm in roof spaces.
Not really a problem.
Listing is generally about outside appearance and internal details only rarely specified.
Sold floors is a prob but much less important than insulating walls and roofs - heat goes up.

 

[rogxwhit]

with a small house and two occupants with a low hot water requirement - shower and washbasin only (the dishwasher and washing machine are cold fill) I've come to the conclusion that a much cheaper and simpler air - air unit would provide sufficient space heating and just use a small electrically heated tank for hot water. Any 'spare money' would be better spent on pv panels.

This is my drift at the moment, and what I'm looking into.

Insulation and solid walls particularly those made of brick and lime cement don’t mix I understand. The walls need to breath and anything that restricts it causes damp which is very unpleasant!

You have to model the heat & moisture transmission and decide where moisture from the internal heated spaces might condense within the structure. This often means that external insulation would be the answer and internal insulation would be a no-no. But that changes the outside appearance of the structure.

heat pumps et al ... are expensive and fairly high tech, which means they aren't accessible to 99% of the population

But they (that '99%') have to have something ...

and are vulnerable to tech failure.

Correct! I suppose there's a maintenance cost too, but the overall service life might be what - 15 years - then a replacement's needed? The cost of which doesn't seem to get mentioned much ...
...

 

[deema]

@Jacob, I also at the moment live in an old chapel that is locally listed, not graded, but it’s similarly restrictive to the outside appearance. I had an expert in historical buildings review what I could do to insulate the property. Their advise was that the walls need to breath on both sides, which also meant I needed restore lime plaster on the inside. He showed me a large collection of photos from historical buildings where he had been called into resolve damp / rot and what had been done to resolve it. In every situation it was insulation / modern materials that had caused the problems. I’m not an expert, but I did have damp problems which after following his advise was resolved. The cost of running the house decreased significantly as the walls fell in moisture content. In the last few years I’ve found that keeping the central heating on to maintain a constant temperature year round has again reduced the heating costs by around 25%, counter intuitive, but it was the bit of the experts advise I had ignored for around 15 years thinking it was an expensive idea. I’m now at a heating cost relatively comparable with typical insulated (not super insulated) houses of a similar size.

 

[deema]

@rogxwhit I know we are getting a little off track. However, outside insulation traps moisture on the inside and it builds up in the walls. A lot of solid wall construction have solid uninsulated without a damp proof floors. The walls as I understand it wick up the moisture from the ground as well as absorbing the damp in the atmosphere within and outside the house. If you put a damp proof course into the walls, the water accumulates above the damp proof course…..had that tee shirt…..the tecky helped me resolve it. Insulation on the outside traps all the moisture onto the inside of the house and creates a lot of damp, that was what I was planning in doing……subsequently my house was locally listed which would prevent it being done going forward.

 

[NormanB]

I’ve been asked by the head of our household to look into air source heat pumps. We are hopefully moving shortly, and she would like to have an eco friendly heating system in the new residence. I’ve done a little bit of research, and it would appear that financially they don’t financially make any sense even including the £5K government grant available.
My initial work looked at the Kw/H generated from 1 litre of oil and 1 cu ft of gas, I’ve used 60% and 90% boiler efficiency to work out how much it will cost for 10.35Kw of heating energy (equivalent to 1 litre of kerosene which my existing property uses). I’ve looked at heat air source heat pumps and used the optimistic 300% efficiency, however, my reading suggests that this drops down to say 200% (and lower) which I haven’t used) when the air is cool in Winter. The saving with todays high energy costs means that it won’t break even for say 15 years. In fact if the house is highly insulated I will be dead before it breaks even. If I look at energy prices before Ukraine, and oil is going back down in price, the payback is again ridiculous / if ever.

It seems that an efficient air source system needs to run as c40C which is too low for hot water so you need an immersion heater to top up the hot water tanks to stop legionnaires growing (which isn’t I believe included in the 300% efficiency figures quoted). The radiators need to be much larger than for a gas / oil boiler and preferably it should be underfloor if you are to attain the same room temperature. Now my wifey likes it warm (a career running hospitals has made her acclimatised to the heat before anyone suggests running the house at a lower temperature)…..around 22C which isn‘t a big temperature differential for a 40C system, I’m actually wondering in a house that may not be very thermal efficient if it will be possible to attain this room temperature.

Has anyone else looked at how cost effective moving to air source is? Am I missing something?

Whats people experiences, the good the bad and the down right ugly in installing and running such systems?

It is a lot less about the heat pump per se than it is about the property and it’s heat loss.

Conventional heating systems compensated for heat loss by high temperature, high energy consumption, cheap energy systems controlled in a quick acting on/off manner. Boilers were generally oversized by orders of magnitude.

Heat pump systems (both ground and air) are low temperature systems where long and slow using weather compensation controls and preferably with underfloor emitters running 24/7 are the name of the game, with the heat pumps sized to heat loss at -2C, with a margin of 10% or so.

UK housing stock heat losses are generally way too high, even the most recently built. Adapting the house to low heat loss is very destructive, disruptive and expensive. The heat pump is the easy bit.

The industry has insufficient skilled system designers and installers and it is the next misselling disaster.

Customers need to educate themselves to avoid a disaster.

I can do no better than recommend the ‘Heat Geek’ website and You Tube channel. They have an approved installer, customer indemnity scheme and probably provide the best training scheme for design and install. I have no connection with them. They are highly regarded.

 

[Lorenzl]

Interesting @deema as I am heading down that path. I did find that you can get insulating lime renders. One has small pieces of cork in and the other creates small air bubbles in it. Neither is that spectacular in insulating but they both breath and do some insulating as well as looking right for the building.

 

[Jacob]

@Jacob, I also at the moment live in an old chapel that is locally listed, not graded, but it’s similarly restrictive to the outside appearance. I had an expert in historical buildings review what I could do to insulate the property. Their advise was that the walls need to breath on both sides, which also meant I needed restore lime plaster on the inside. He showed me a large collection of photos from historical buildings where he had been called into resolve damp / rot and what had been done to resolve it. In every situation it was insulation / modern materials that had caused the problems. I’m not an expert, but I did have damp problems which after following his advise was resolved. The cost of running the house decreased significantly as the walls fell in moisture content. In the last few years I’ve found that keeping the central heating on to maintain a constant temperature year round has again reduced the heating costs by around 25%, counter intuitive, but it was the bit of the experts advise I had ignored for around 15 years thinking it was an expensive idea. I’m now at a heating cost relatively comparable with typical insulated (not super insulated) houses of a similar size.

We had bad expert experience here.
The previous owners had employed damp proofing specialists to sort out problems and they had done the worst possible job. They'd fixed semi rigid DPM to walls but starting at the bottom and lapping 1 metre sheets as they went up. As a result water condensing between the outside wall and the DPM would drain down and through the lap joint to the inside of the building. They created a way of bring moisture in! A bit like laying roof tiles the wrong way round.
They'd also neglected to unblock underfloor vents and sundry other details and encouraged dry rot.
So don't take too much notice of experts - some of them wouldn't even make the grade as DG salesmen!
The main thing about insulating external walls in the inside is to make it continuous with no gaps so that internal room water vapour can't condense on the masonry. Various ways of doing this - e.g. sticky tape over joints on rigid board. Internally no piercings for cable or pipes - all surface mounted
No probs here now but I have various monitoring points to look at just in case.
Energy bills all in, is now £120 a month (just gone up) and it's a big building.

PS also had very bad advice about lime mortar. If doing it again I'd use the tried and tested ready mixed and bagged options as discussed elsewhere on the forum.