# Air source Heat Pumps any good?



## deema (5 Aug 2022)

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?


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## Fitzroy (5 Aug 2022)

This thread was about the samilar (same/similar) subject just recently. You have however reached the same conclusion that I got to, from a basic economic analysis ie cost vs return, it's a tough sell.

The things that are more difficult to estimate:
- It is likely to add value to your house as it becomes a more desirable requirement, or if the government begins to mandate a transition then houses without are likely to be discounted by the cost of install by new buyers.
- The future differential between gas and electricity prices could grow significantly. I'd not be surprised to see taxes grow on gas/hydrocarbons, so as the electricity supply moves away from gas/hydrocarbon as it's energy source this differential will increase.

Fitz.


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## mikej460 (5 Aug 2022)

The biggest hurdle is that are very expensive, you will need larger, much more expensive, low temperature, high efficiency radiators and/or underfloor heating. Also it still need electricity to power the compressor so unless your new house is super-insulated this will result in very high electricity costs to maintain the house at 22 degrees and also preheat your HW. All this put us off ASHP and we bought a Wood Pellet Biomass boiler instead which, after 7 years use, is now costing 30% more for pellets than the same time last year. In cashflow terms the cost of the pellets is covered by our RHI grant but this ends in December. That said we use 8 pallets of pellets per year at £395 (current price) so £3160 pa to heat a largish 3 bedroom cottage; they are bound go up more in 2023.


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## AJB Temple (5 Aug 2022)

This was also on radio 4 yesterday. An added aspect is that as it currently costs more to run an ASHP than gas, the energy efficiency rating required for selling a house is actually worse for an ASHP set up. 

Personally, unless I had a wind turbine and solar already to provide electricity, I would not dream of installing an ASHP. I would look at a GSHP if I were building a new passive house and could spec the heat ducting system from scratch. 

ASHPs are, I might suggest, promoted by politicians who don't have a clue how they work. Comparisons with fridges, which are often heard, including on the programme yesterday, are absolutely stupid. A fridge is a small, very efficiently sealed, highly insulated double skinned box. Unless your house is similar, and 99% are not, then the comparison is just misleading nonsense.


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## Nic Rhodes (5 Aug 2022)

I use an ASHP to heat an outdoor swimming pool but would be very reluctant to recommend them to a domestic user atm.


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## Lorenzl (5 Aug 2022)

It is funny the electric boiler I am going to install is stated as 100% efficient BUT it is only gets a "*ErP Rating *D(Heating) A(Hot Water)" as :


> So, while an electric boiler can heat water with little to no heat loss, giving the unit a 99-100% efficiency, the fuel factor sees the ErP rating appear low as the generation back at the power station produces high volumes of carbon.


from the Boiler guide website

This can be a bit deceiving when searching for an electric boiler.


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## D_W (5 Aug 2022)

I have an ashp mini split on a supplemental room (not tied in to the main gas/house ac unit). This is a small house, too, so it's just circumstance, not gluttony. 

Mine is a 14 EER/ 21 SEER 15kbtu mitsubishi that's been in place for about 7 years. I have given up on the idea of routine maintenance - it's a wallet emptier. with the exception of cleaning the screen and if the unit ever gets weak and needs a charge, I will do that. 

The reason? The installation is dead simple and I will just replace the thing if it craps out in 15 years.

Which brings me to my next point - FIL and two BILs, all same side of the family, have full house GSHP replacing oil in two cases and propane in another - the three can all be expensive here and leave you finding A/C elsewhere. 

They have had good experience except all three have had the same warranty repair to a defective board - each has a gaggle of boards and is complex. when the boards fail, the service techs have trouble getting the right board ordered and installed and configured back to the systems because they're efficient, but also want to be everything to everyone (enormous number of zones, wanting connectivity with devices, etc). Cost of their systems was incurred in an area that's not heavily union and probably on the low side. 3 well vertical, I believe, maybe 4 for one of them, and the total cost was about $16k on average. 

The installing company insists on servicing them once a year, and they charge $300 for it. I have no idea what they do, and neither does my FIL - and he is cheap (eventually convinced his prior plumber to show him how to clean an oil furnace himself annually - he is cheap, but diligent). 

If you're somewhere cold and you want year-around efficiency, GSHP will do it. But I understand there is an effective life on the wells before something fails in them and they need to be redone. Maybe 20 years?


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## D_W (5 Aug 2022)

Lorenzl said:


> It is funny the electric boiler I am going to install is stated as 100% efficient BUT it is only gets a "*ErP Rating *D(Heating) A(Hot Water)" as :
> 
> from the Boiler guide website
> 
> This can be a bit deceiving when searching for an electric boiler.



if this is resistive heat, that figure is damning as even an ASHP will beat it by about 3 times in most conditions, two in very cold. 

I'm in the states, and my ASHP mini will run down to -13F and I've never noticed a big change in the electric bill. I heats about 225 SF that's off the house for around $25-$30 a month in electricity. It shines in the summer as the cooling rating is done at 97F, which it rarely gets to here, and it will generate closer to 20k btu on 1 kw on most days. 

ASHPs are run in up cost to a ridiculous level, though. The local mitsu dealer wanted $6k to install the unit that I have. The contractor I used to finish out my back room gave me his plumbing supply place's contact info to order through him and the unit cost $2100. $200 for electrical run to it and a whip disconnect and the contractor's HVAC guy installed the thing for $750 (4 hours of work for an older plumber and his helper, and they could've done what they did in 1 - they were slow and then spent 2 hours playing with the unit I think more out of curiosity). I could have and should have installed it.


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## rogxwhit (5 Aug 2022)

No experience or answers but a couple of links that may (or may not!) assist your research -

1.





Search


This forum is used by green building professionals, architects, builders, developers and green building owners to discuss all subjects related to green building.




www.greenbuildingforum.co.uk





2.


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## Trainee neophyte (5 Aug 2022)

As someone who heats their home at no cost from excess wood which is is a harvest byproduct, I feel for you all. Given the insane prices being quoted for fuel/electricity this winter, and the legislated requirement to change to a "greener" system, I wondered what the overall cost of buying a piece of land (or several small pieces) to coppice willow might come out at, written off over say 15 years. 









The Willow Bank - Grow Your Own Firewood - The Copse System


Willow, grown as a Copse, is the Fastest Growing Tree in the UK.... : Plant 10 Copses (1/4 Acre) and harvest 2 Tonnes of dried firewood each year




www.thewillowbank.com





"*Growing a Willow Copse* is an ideal way of producing logs for your home or workshop.
100 “Super Willows” planted 1m apart in a *10m x 10m square Copse* will produce *1 Tonne of seasoned firewood* every five years.

Plant* 5 willow Copses*, harvest one each year and produce* a Tonne *of seasoned firewood to heat your home or workshop every winter.

Plant *10 willow Copses* (1/4 Acre) and harvest* 2 Tonnes *of seasoned firewood each winter and so on…."


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## Lorenzl (5 Aug 2022)

I like the "a Smug Willow Copse Owner" photo. I thought burning wood was "bad" but I suppose as you are growing what you burn it must be virtually carbon neutral as they say?

What do you burn for the first 5 years?


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## D_W (5 Aug 2022)

That seems like a lot of work. I calculate a minimum for the consumption (heated with wood in the US as a kid) we had, 2 acres of clear land with good sun exposure would be required. 

It would give someone some exercise, though. 

Particulate pollution is drawing some notice here in the states because of the subsidy for biomass heating in public buildings. They pollute far more than burning natural gas, and at this point, even vs. oil. Solving that will just add to their disadvantage.


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## Sideways (5 Aug 2022)

Heat pumps as a retrofit to an existing house don't make sense to me, but I do wonder about simple aircon fed from our solar, as a supplement to the gas boiler.
A quality 6kW mitsubishi split with two indoor units cost about £2k plus installation.
These can be run as a cooler or a glorified fan heater with (by the look of things) a 300% COP most of the year in the UK. A lot of asia uses split aircon units for heating through winters colder than ours....
For just a modest outlay I suspect I'd get quite a lot of free heating from one of these and a useful reduction in the gas bill over the year. Once you have solar PV it's all about using up what it generates.


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## D_W (5 Aug 2022)

Sideways said:


> Heat pumps as a retrofit to an existing house don't make sense to me, but I do wonder about simple aircon fed from our solar, as a supplement to the gas boiler.
> A quality 6kW mitsubishi split with two indoor units cost about £2k plus installation.
> These can be run as a cooler or a glorified fan heater with (by the look of things) a 300% COP most of the year in the UK. A lot of asia uses split aircon units for heating through winters colder than ours....
> For just a modest outlay I suspect I'd get quite a lot of free heating from one of these and a useful reduction in the gas bill over the year. Once you have solar PV it's all about using up what it generates.



I'm guessing that your 6kw rating would be in line with what my unit is (with coil running, mine will go to 2kw, but it is uncommon for it to draw like that. without coil, it seems to be more around 1kw - its consumption without coil going all out.. 

Effective heat output is the same as 3 -4 times that of the portable plug in heaters that run around 1500 watts, same output but 2kw (for the split) when it's cold enough for the coil preheater. 

The draw for the machines in asia is probably that they're not that demanding in current draw, and they can be installed pretty much through any small hole and set up without having exhaust or much relief from a building. 

Not sure on gas costs, but could be used effectively to heat a point and area around it to normal comfort and wind the gas back everywhere else.


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## Jacob (5 Aug 2022)

Woodworkers need woodburners. I don't do a lot nowadays but even that can produce sawdust, chippings, offcuts to keep the fire burning for some time. I also collect anything going including pallets and old bits of furniture and people bring it in knowing we'll have it.
The burner is a Dowling Sumo which is supposed to do 12kw and gets hot in a few minutes. The squat shape suits sawdust as well as everything else. Also coal, though never tried it.
The only prob could be storage but I've got lots of room luckily.
Also does old cardboard, paper etc which get the room hot very quickly.
Very efficient, hot, zero carbon, free fuel
PS and a smaller Dowling Firebug in the workshop


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## Inspector (5 Aug 2022)

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


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## Dee J (5 Aug 2022)

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. There capital cost, even taking into account financial inducements have been brutal and the installations over complicated. Even when working at their best they're pretty expensive to run and I shudder to think what future maintenance /repair costs might be when the controls stats valves pumps etc start to play up. For myself, 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.


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## clogs (5 Aug 2022)

over the years of looking at these systems, the only way they make sense is if ur house was built as a super insulated property ...this includes triple galazing with solar gain glass and the list is endless....retro fitting is not an efficient option esp with the avg Brit housing stock.....
with a sup/ins house u dont need any of those expensive heat pumps etc anyway.....u could just use a couple of oil radiators.....cheap as chips...
I worry about the maintainence and break downs......
esp if u need a so called heating engineer....
but who's got the money for all this...?. 

u have to make do with what u have....
if I was back in the UK...(that will never happen) I'd just heat the rooms I need to use....
AND wear a jumper.....
my Dutch friend in warm SW France has such a heating system but when he put in the new floors (barn conversion) he piped it up underfloor.....all the years I've known him he's had to pay extra for wood to burn (top up heating) plus elec for the emersion heater.....so what's the point....?
Elec solar roof panels were not available at the time of his conversion....
His conclusion when it eventually breaks he'll bin it and fit a wood burning boiler....
simples.....
If u wanna save money I think the best option is elec roof panels or move somewhere warmer...lol.

we just had the worst winter in 35 years, so had to burn 2.5 - 3 ton of olive wood.....
norm winter is 1-1,5.....BUT we live in the sticks and thats what every body does for heating n hot water....
Next year we'll have solar panels (off grid) and that will help us a lot.....


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## baldkev (5 Aug 2022)

I believe a u.s based company is working at ways to make heat pumps viable.... bill gates is apparently backing them, but i dont know the specifics


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## Sideways (5 Aug 2022)

A really high quality solar install is costing me £24k ish for 9kW peak, 16kWh of batteries + smart controls and charging. It's a lot of money but in the last 4 months alone it's produced 3.6MWh which was our entire annual elec consumption last year. It will do even more when the batteries arrive from China.
This project is a leap of faith as to whether it ever really pays back, but do this when you retire, maybe earlier, and it should last your lifetime.
I wonder how much heat pump systems cost in comparison and how much energy they provide. And 7 yr warranty at best (?) vs 25 year for solar panels.

The great thing about PV is that the energy is very high grade so if you want your water boiling, you can have it that way.
The downside is that 8kWh daily average in December-January will meet a lot of our needs but won't heat the house. In winter we'll still depend on gas. For 6-8 months of the year, we should be near self sufficient.

And as another benchmark, 5kW of 15 yr warranted panels, 5kWh of battery and a car charger cost a friend about £11,500 last week.


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## Spectric (5 Aug 2022)

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.


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## Terry - Somerset (5 Aug 2022)

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"


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## Phil Pascoe (5 Aug 2022)

Inspector said:


> 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.


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## Nic Rhodes (5 Aug 2022)

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.


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## D_W (5 Aug 2022)

Dee J said:


> 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.


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## D_W (5 Aug 2022)

Nic Rhodes said:


> 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.


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## mikej460 (5 Aug 2022)

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.....


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## Dee J (5 Aug 2022)

D_W said:


> 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.


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## D_W (5 Aug 2022)

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.


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## D_W (5 Aug 2022)

Dee J said:


> 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.


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## Chris70 (6 Aug 2022)

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


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## Jacob (6 Aug 2022)

Chris70 said:


> .........
> 
> 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.


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## deema (6 Aug 2022)

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.


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## Jacob (6 Aug 2022)

deema said:


> .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.


deema said:


> ..... 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.


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## rogxwhit (6 Aug 2022)

Dee J said:


> 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.



deema said:


> 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.



Jacob said:


> 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_ ...



Jacob said:


> 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 ...
...


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## deema (6 Aug 2022)

@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.


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## deema (6 Aug 2022)

@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.


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## NormanB (6 Aug 2022)

deema said:


> 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.
> ...


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.


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## Lorenzl (6 Aug 2022)

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.


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## Jacob (6 Aug 2022)

deema said:


> @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.


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## Lard (6 Aug 2022)

Sideways said:


> Heat pumps as a retrofit to an existing house don't make sense to me, but I do wonder about simple aircon fed from our solar, as a supplement to the gas boiler.
> A quality 6kW mitsubishi split with two indoor units cost about £2k plus installation.
> These can be run as a cooler or a glorified fan heater with (by the look of things) a 300% COP most of the year in the UK. A lot of asia uses split aircon units for heating through winters colder than ours....
> For just a modest outlay I suspect I'd get quite a lot of free heating from one of these and a useful reduction in the gas bill over the year. Once you have solar PV it's all about using up what it generates.



The issue there, is that the sun doesn’t shine in the evening ie when heating is more likely to be required and so you’re then either dependant upon the grid or, if you can afford it (more below) a battery backup system.

We had a 4.2kw solar system fitted about 3yrs ago and it works as well as we expected…..payback between 8-10yrs.…..so much so that a few weeks back I contacted the same fitting company and enquired about adding battery backup. Their own estimator/designer gave me some very basic cost info as well as technical specs and sent me away to do my own simple monetary calculations. A few days later I confirmed (to his agreement) that it was NOT a financially viable project for us…..he then pointed out that he has several enquiries per month where he has to, unfortunately for the company, burst bubbles by illustrating how much the sums simply do not stack up at current costs. He genuinely doesn’t want customers wasting money.

We have a 3 bed bungalow (now with attic conversion) and in the warmer months it only uses ~3-4kw per day (the solar panels obviously helping by doing their thing as they regularly produce 20+ kw/day). However, from roughly mid October to January, when we’d need even more electricity for evening heating, there are numerous days where we don’t even produce 5 kW!

Based on a rough 5kw battery cost of £4k the simple calculations (for us) are as follows:-

If our house needed 5kW in an average evening (highly unlikely but let’s run with it) then, in theory, we would be charging and discharging the 5kw battery once (ie one cycle) per day. At £0.20 per kw, this would mean a saving of £1/day = ~£350\yr……meaning that over ten years we would save ~£3500……given that over this period we may have to change the inverter the overall cost (battery and inverter) would be roughly the same as the savings…..And so, for us anyway, it isn’t worth the financial risk?

I’m also concerned (having read up on the battery’s chemistry etc) that in the winter months, when the battery isn’t being charged fully, would this lead to battery degradation over time resulting in a reduced battery life?

When you sit down and actually think about it (in our case anyway ) we’d only be saving £1 per day which, on first impressions, seems crazily low given current electricity prices but everything adds up when you multiply it by 30 or 365 days.


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## Phil Pascoe (6 Aug 2022)

Chris70 said:


> 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’re not millionaires, but we are able to do our ‘green bit’.
> 
> Chris


It's nice when other people pay for your green credentials, isn't it? (Not meaning to be personal in any way - I don't blame you.)


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## nickds1 (6 Aug 2022)

We've had a 3-phase GSHP here for 17 years and it's never missed a beat. It's been serviced once in that time with only minor tweaks needed.

Post in thread 'Suggestions for future heating system' Suggestions for future heating system


We installed it at the same time as doing our self-build, so had the machinery onsite, thus keeping the cost down a bit. At the time, it cost about 5K to install with an RoI of about 3 years.

Firstly, the hot water that a heat pump delivers is just about right for 99% of uses - the sterilisation cycle every week or two costs a couple of quid at current rates.

We have a measured average cop of 3.5 and I have fairly sophisticated power monitoring on all aspects of the site, based round an Emporia system (see elsewhere on this site). If needed, we easily get 300lts of 40-45C water every hour day or night, summer or winter. Since the kids moved out, our hot water usage has plummeted anyway.

For ANY heat pump to be effective, you need good insulation and a house designed for it. Retrofitting is always a compromise and is highly unlikely to be anywhere as efficient as a system sized and designed alongside the property its intended for.

Heat pumps are not a panacea, but they are a step in the right direction, especially when used in the right building and with "green" electricity.

I fully concur that the government simply don't understand the complex issues involved.


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## Jacob (6 Aug 2022)

Who needs heat pumps?


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## Misterdog (6 Aug 2022)

My wife likes it at 22 C you say.



> New law in Spain.
> Air conditioning cannot be lowered below 27 degrees in summer and heating cannot exceed 19C this winter, while shop fronts must go dark by 10 p.m., according to the decree passed Monday.
> 
> Similar measures have already been put in place for public administration buildings, while they remain voluntary for houses.











Spain orders temperature limits for businesses in sweeping energy saving decree


Authorities say move will help Spain reach goal of reducing gas consumption by 7 percent.




www.politico.eu





I think similar legislation should be adopted in this country, if we are serious about reducing global warming.

I agree that air source heat pumps make no sense commercially or even ecologically at this time. We have had to re-open coal fired power stations to provide electricity to 'not' heat our homes.









UK close to deal with EDF to keep coal-fired power station open


French firm in talks to extend life of Nottinghamshire plant to shore up Britain’s winter energy supplies




www.theguardian.com





I live in a detached house built in 1865 the only option is plenty of thermal layers..


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## Misterdog (6 Aug 2022)

Lorenzl said:


> It is funny the electric boiler I am going to install is stated as 100% efficient BUT it is only gets a "*ErP Rating *D(Heating) A(Hot Water)"



Solar panels are only 20% efficient when new dropping to 18% after a couple of hours of use.

Though as I recall steam engines were only 9% efficient..


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## Skydivermel (6 Aug 2022)

deema said:


> 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.
> ...


I've been in the industry for 27 years. There are many factors to consider prior to making an informed decision. Don't listen to you mate down the pub who has watched a YouTube video on ASHP. Firstly you need to do heat loss calculations for every room in the house. All 4 walls and the window(s) sizes. Are walls solid, cavity, cavity with insulation, internal, external etc. Once calculated this will give you the total heat loss of the property thru walls. Windows, are they single glazed, double glazed etc. If double glazed what's the air gap? It used to be 16mm now it's 20mm. Are the frames wood or Ali. This will give heat loss thru the windows. Once calculated this will give you the heat loss for every room.

Next look at every radiator in the house. What type are they (K1 single, K2 double, K3 triple (panels)) Then look at the relative heat output from each radiator at 80deg C, 60deg C & 40deg C. Next look at you loft insulation and floor types. Is the ground floor solid concrete, suspended, etc, first floor is usually suspended floor boards or chip board. How much loft insulation do you have. Once you have calculated all the above this will give you the total heat loss for the whole property.

Most ill informed people think that they'll have to change every radiator in the house for some super sized monstrosity. Not so. Example, if the heat loss for a room is say 700 watts and you have a 600 X 600 K2 radiator in there and the heat output for that radiator at 40deg C is 800 watts then why change it? Do this exercise first before even thinking about an ASHP.

Next, hot water cylinder. Legionella grows at temperatures below 55deg C. A typical 200litre cylinder will change it water volume around once every day in a typical household. The temperature of a cylinder only needs to be set at between 38 & 43deg C max otherwise you have to blend in cold water to get it to this temperature. Any hotter and it will burn you. For safety sake we set cylinders to achieve 61deg C once a week to eliminate legionella risk.

Next look at your heating circuit pipe sizes. If it's this new 8mm micro bore plastic forget it. You'll have to change all your pipework. Most properties have 22 & 15mm copper pipe. If that's the case then your good to go although I would add that power flushing the heating circuit is always recommended to remove any crud in the system therefore increasing efficiency. There are other options to help with efficiency, flow rates, heat distribution, headers or buffer zones, weather compensation etc but don't want to get too technical here.

Without trying to offend, your average plumber wont know or cant do the correct heat loss calculations nor will they be able to size and design a system to run at max efficiency at 40deg C. Most of them can fix a shower or a WC or install a new boiler, (all they do is look at the current boiler kW rating and install a new one of the same rating) 

To sum up. It's a highly technical exercise to see if a domestic ASHP is suitable for a property. Government make all these outrageous claims that we'll be a nation of heat pumps by 2030 but in reality we need to look firstly at the correct training, sizing and installation methods before embarking on this journey.

Systems are getting better and we can get water temperature of 70+ Deg C on some systems now but those systems are not suitable for all properties. Hope this helps some of you.


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## deema (6 Aug 2022)

@Skydivermel thank you, that’s really interesting.


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## deema (6 Aug 2022)

The potential (we havent yet signed our lives away just going through the process) new property was built I think around 1900, it’s recently been fully renovated and extended. Triple glazed, loads of roof insulation and some parts (extension) has underfloor heating. It has a LPG tank and boiler as living in Cheshire mains anything is very rare other than in the towns. All rooms have a due south facing aspect so lots of solar gain. However the EPC is E, I’m told a lot of why it’s so low is due to the LPG??


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## Just4Fun (6 Aug 2022)

nickds1 said:


> For ANY heat pump to be effective, you need good insulation and a house designed for it.


I don't think you can generalise like that. I seriously doubt that our house, built in the 1890s, was designed for a heat pump but our GSHP works better than any alternative available to us.


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## ScottandSargeant (6 Aug 2022)

I live in an old timber frame house with extensions. I spent a lot of time improving the insulation, fitting high performance sashes and other household improvements when I took the plunge of my first ASHP 10 years ago, getting rid of an lpg boiler. My first ashp only heated the water to 50 degrees. It mysteriously failed and had to be replaced after 3 years with a generous help from the Swedish manufacturer CTC. The replacement can heat the water to 60 degrees (I only set to 55 tho as efficiency declines as temp increases). Servicing cost is minimal. It is controllable from my phone as many things are nowadays. It doesn’t blast out heat like a traditional radiator, but if you insulate your house you don’t actually need that. I run the old radiators @ 35 degrees and the underfloor heating area at 30. 

Overall It is brilliant, I was lucky enough to get an RHI grant which helped with the cost too. Would I go back to an LPG or oil boiler….er no. It has saved me thousands in energy bills over the years. 
Would I consider anything else? Maybe a wood pellet system, but they can be more fraught with problems of pellets getting moisture damage and clogging feed mechanisms. 
Over all it’s a sensible way forwards but you need your house not to leak heat (but who wouldn’t want that?)


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## Lorenzl (6 Aug 2022)

@deema Yes probably the same as I posted about our boiler. It will be the cost of producing the LPG and probably the cost of transporting as well.


> So, while an electric boiler can heat water with little to no heat loss, giving the unit a 99-100% efficiency, the fuel factor sees the ErP rating appear low as the generation back at the power station produces high volumes of carbon.


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## Lorenzl (6 Aug 2022)

ScottandSargeant said:


> I spent a lot of time improving the insulation, fitting high performance sashes


How much did that all cost?


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## Sideways (6 Aug 2022)

Skydivermel said:


> Firstly you need to do heat loss calculations for every room in the house


This suggests I'm on the right track. Thanks.
I decided to write an excel sheet to do exactly these numbers in detail so that I could look at what changes would have the biggest bang for my buck and exactly how much heat I need in each room. Work's in progress but it's already interesting.

Our place is a small 1979 detached with a disproportionally large roof (hence the long term desire to exploit it with solar). We don't have any damp problems since I rectified the original builder's habit of bridging the DPC with plaster (shoddy workmanship) but I've heard too many horror stories and I've avoided cavity wall insulation ever since we bought the place. 

The down side is that you have fat chance of receiving any government RHI or grant if you won't install cavity insulation. I believe that these schemes just allow approved contractors to hoover up tax payers money and frankly that you can get a better job done outside them if you take time to educate yourself. Still, I want to learn what my decision not to install cavity insulation is costing me. 

In my searches for U values for a range of housing elements and construction materials I found a real interesting report by the BRE that measured actual U values of walls across a good number and range of UK legacy houses. It's always nice to find data where the authors are prepared to document their methods to justify it.



https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/409428/In-situ_u-values_final_report.pdf


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## ScottandSargeant (6 Aug 2022)

Lorenzl said:


> How much did that all cost?


It was part of an extension rebuilding with lots of new windows so it was a little hard to quantify in flat terms.
I doubled the square footage of the house and reduced the heating bill… and the house feels warmer.


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## Br5d (7 Aug 2022)

if you have a passive NZEB house then maybe they make sense, if not then the upgrade to that level would be your 1st priority.


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## Jacob (7 Aug 2022)

Jacob said:


> Woodworkers need woodburners. I don't do a lot nowadays but even that can produce sawdust, chippings, offcuts to keep the fire burning for some time. I also collect anything going including pallets and old bits of furniture and people bring it in knowing we'll have it.
> The burner is a Dowling Sumo which is supposed to do 12kw and gets hot in a few minutes. The squat shape suits sawdust as well as everything else. Also coal, though never tried it.
> The only prob could be storage but I've got lots of room luckily.
> Also does old cardboard, paper etc which get the room hot very quickly.
> ...


Forgot to add - bigger wood stoves are better - a small fire burning hot in a large stove with a larger surface area is more efficient than the opposite.
Also much faster in terms of heat generation - you can get a room warm very quickly with small stuff packed loosely with the vents open to burn it fast.
This is roughly what is behind a rocket stove at one end of the scale, or a gasification boiler at the other, i.e. fast hot burning for greater efficiency.


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## PDW125 (7 Aug 2022)

Chris70 said:


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



If it is an unvented cylinder - ie one with no header tank and at mains pressure - it is not required. Get it turned off


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## PDW125 (7 Aug 2022)

Skydivermel said:


> Next, hot water cylinder. Legionella grows at temperatures below 55deg C. A typical 200litre cylinder will change it water volume around once every day in a typical household. The temperature of a cylinder only needs to be set at between 38 & 43deg C max otherwise you have to blend in cold water to get it to this temperature. Any hotter and it will burn you. For safety sake we set cylinders to achieve 61deg C once a week to eliminate legionella risk.



agreed with everything you said until you got to that point ..!! If it is a sealed unvented cylinder then the legionella risk is nil. Legionella requires air entry to the system along with moisture. It will not grow in a closed chlorinated water source and there are no reported cases anywhere of it in a domestic environment in the last 20 years. Legionella cycles just cost money, they do not actually do anything.


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## jonw1664 (7 Aug 2022)

Jacob said:


> Depends on the details but generally not a problem.
> 
> 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.
> ...


Re - “listing is generally about outside appearance” I wish that was the case. My listed buildings officer will not allow any insulation to be fitted to the inside of the walls as it “hides and damages the historic fabric” this historic fabric has been hidden to the world for 250 years but she will not be moved. This means I cannot insulate the house to a point where UFH / GSHP/ASHP are viable so despite my desire to be green I have reluctantly purchased a new oil boiler. The listed buildings police just don’t get that the buildings need to be practical if they are to be lived in and therefore maintained. I am all in favour of preserving our heritage, that’s why I took on the challenge of owning a listed building but a slavish adherence to “everything that’s old must be left untouched” will lead to empty buildings that fall down, some sensible pragmatism is required. Rant over!


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## Phil Pascoe (7 Aug 2022)

Around here they list buildings and watch them fall down for a half a century. One nearby is listed because of the superb original coving .......... which is made up of rubber and other materials from packing crates after WW2.


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## Skydivermel (7 Aug 2022)

PDW125 said:


> agreed with everything you said until you got to that point ..!! If it is a sealed unvented cylinder then the legionella risk is nil. Legionella requires air entry to the system along with moisture. It will not grow in a closed chlorinated water source and there are no reported cases anywhere of it in a domestic environment in the last 20 years. Legionella cycles just cost money, they do not actually do anything.


As you say if it's a sealed system. But all systems will eventually get oxygen into them so once a week for 2 hours at cheap rate electricity is worth it in my book. However one hell of a lot of UK properties still have open vented systems. Our housing stock is some of the oldest in Europe and we do very little to insulate them. If Govt gave grants for the correct insulation then we could all run ASHP. BUT if insulating to a very high degree then we have the issue of moisture retention which leads to the necessity of the correct ventilation system for the property.

It's a never ending circle of expense for the homeowner. 

The current house building boom we're going thru worries the life out of me. We're building the slums of the future. Think back to when we were kids (me was 1956 - 1970) we had some of the coldest and draughty houses with ice on the inside of the windows. However we were also more healthy then as a nation than we are now.


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## mikej460 (7 Aug 2022)

Skydivermel said:


> Think back to when we were kids (me was 1956 - 1970) we had some of the coldest and draughty houses with ice on the inside of the windows. However we were also more healthy then as a nation than we are now.


Bit of a stretch this, although as a young boy I do remember 1963 ice leaves on the inside of my bedroom window (brand new house with no central heating); I think our current state of health is more down to not living in slums, better diet, reduced smoking, better public health education and better medication.


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## Lorenzl (8 Aug 2022)

I think that was the way in the late 60's/70's @mikej460 The first house my parents brought had one electric fire in the lounge only and I remember waking with frost on the inside of the bedroom windows.
My second house had one gas fire in the lounge and a small electric fire in the hall.


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## Cooper (8 Aug 2022)

Skydivermel said:


> However we were also more healthy then as a nation than we are now.


Only anecdotally, but in my cold 1950s childhood lots of the elderly didn't get much past 70. We've had a boom in folk reaching their 90s since central heating became ubiquitous. But I must agree about the state of housing stock.
I think its a cultural thing, thinking being cold is healthy. Bedroom fan lights open on winter nights, one bar electric heaters if you were lucky to get into your pyjamas, then two or 3 thick woolly blankets, an eiderdown and on really cold nights your coat over the top.
I have a theory that our rulers were brought up in freezing public school dormitories and think being cold was good for the nations character, hence pathetic energy regs. in the 50s and 60s.

Where my daughter lives, in a Munich suburb, they have district ground source heating with heat-pumps in the homes. The modern buildings have very high spec insulation and older buildings far better than here. They also have an obligation to regularly upgrade boilers in homes that are off grid. Qualified trades people know that there will be a regular supply of work, not like ours, with energy policy turned on an off at the whim of the current Prime Minister. (will green levies still be in place when the next one shuffles in?) You would think the current energy and climate emergencies would make zero carbon the most important policy but it seems cutting council tax in Tunbridge Wells is far more important.


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## dickm (8 Aug 2022)

Jacob said:


> Forgot to add - bigger wood stoves are better - a small fire burning hot in a large stove with a larger surface area is more efficient than the opposite.
> Also much faster in terms of heat generation - you can get a room warm very quickly with small stuff packed loosely with the vents open to burn it fast.
> This is roughly what is behind a rocket stove at one end of the scale, or a gasification boiler at the other, i.e. fast hot burning for greater efficiency.


Not convinced about that. When we moved into our present house (near passivhaus spec) it had a huge Vermont Castings stove in the living room. We didn't have it running all the time, and my impression was that it took a heck of a long time to warm up to efficient burning. Replaced it with a 5kW Squirrel, which heats the whole house via a forced ventilation/heat recovery system, and to us, it seems much better.


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## Jacob (8 Aug 2022)

dickm said:


> Not convinced about that. When we moved into our present house (near passivhaus spec) it had a huge Vermont Castings stove in the living room. We didn't have it running all the time, and my impression was that it took a heck of a long time to warm up to efficient burning. Replaced it with a 5kW Squirrel, which heats the whole house via a forced ventilation/heat recovery system, and to us, it seems much better.


You can kick off efficient burning very quickly by just having loose *dry* small stuff in there, not packed tight, which should burn off like a rocket if the vents are open and flue is OK. Might have to keep adding small stuff to keep the temperature up, and then start putting in bigger stuff gradually.
I had a Squirrel too but it was a high maintenance job needing fire bricks and baffles at regular intervals.
The Dowling stoves are sheet steel welded and totally maintenance free so far (20 years or more) except for broken glass accidents (twice).
The main thing is to avoid slow burning - a little and often rather than packed in tight.
For maintaining background heat you need thermal mass:
Gassification boilers give you fast hot burning with heat saved in a thermal store (big water tank).
The primitive (?) Russian version involves small hot fires in massive masonry constructions to store heat.


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## Misterdog (8 Aug 2022)

Jacob said:


> The primitive (?) Russian version involves small hot fires in massive masonry constructions to store heat.



Known in this country as the chimney breast.
A ton or two of masonry which serves no structural purpose.

Some of the Russian and other very cold climate stoves doubled up as a setee and/or bed.

We think we are hard done by if we cannot have our homes heated to 22/23 C.
My father was at Stalingrad in WW2, the temperature that winter was apparently minus 20....to minus 40.

Turn on the 'heating' and a sniper would shoot you.

Still many will complain that we are freezing to death this winter and blame our 'Fascist' government.


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## artie (8 Aug 2022)

How about we learn to be happy at 17Deg instead of 22. 

Saves heating costs, helps the planet and aids in weight loss as your body will burn fat to keep warm.

Win, win, win.


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## Droogs (8 Aug 2022)

that's still too hot, 16 C is ideal room temp for me CH set to come on at 14 and off at 18


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## Lorenzl (8 Aug 2022)

What we want is an over active thyroid in the winter and under active one in the summer. You could do it with drugs and it would be cheaper


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## deema (8 Aug 2022)

Unfortunately, as you age, you feel the cold more and need a higher temperature to remain comfortable. When your young, your body is able to generate heat to keep you warm, as you slow down and lose muscle mass that ability decreases. There are a number of conditions that also mean you need a warmer temperature to feel comfortable, at 17 degrees that just 1 degree warmer than the minimum temperature for an office environment. I know that if I had run the offices in my company’s at 17 degrees a certain sex would have lynched me, the minimum acceptable temperature was considered to be 21C!


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## mikej460 (8 Aug 2022)

deema said:


> Unfortunately, as you age, you feel the cold more and need a higher temperature to remain comfortable. When your young, your body is able to generate heat to keep you warm, as you slow down and lose muscle mass that ability decreases. There are a number of conditions that also mean you need a warmer temperature to feel comfortable, at 17 degrees that just 1 degree warmer than the minimum temperature for an office environment. I know that if I had run the offices in my company’s at 17 degrees a certain sex would have lunched me, the minimum acceptable temperature was considered to be 21C!


I think my wife must have worked there...


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## Misterdog (8 Aug 2022)

Because they all wanted to work in summer blouses ?


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## dickm (8 Aug 2022)

Jacob said:


> You can kick off efficient burning very quickly by just having loose *dry* small stuff in there, not packed tight, which should burn off like a rocket if the vents are open and flue is OK. Might have to keep adding small stuff to keep the temperature up, and then start putting in bigger stuff gradually.
> I had a Squirrel too but it was a high maintenance job needing fire bricks and baffles at regular intervals.
> The Dowling stoves are sheet steel welded and totally maintenance free so far (20 years or more) except for broken glass accidents (twice).
> The main thing is to avoid slow burning - a little and often rather than packed in tight.
> ...



Can't disagree with most of that, just that my experience of the VC one was that its thermal mass was useful IF running all the time, but even doing exactly what you say, it was a pig to get going for intermittent use. 
Don't know the Dowling stoves, but had read that welded sheet was inferior to CI. I'll bow to your superior knowledge, but stick with my second Squirrel! Had one in last house but one, which fortunately the buyers didn't want, so it moved to our last house and worked well for about 17 years; probably still going strong. After falling out with the Vermonster, got another Squirrel which has been in for about 14 years.
Working with some Swedes many years ago, and they had one of those huge masonry surrounds to a small fire. 
Could look up the exact date we were there, because our very dour Swedish "minder" was sitting in his car on a bleak airfield when he suddenly shot out of the car, waving his arms and shouting gleefully "She's gone, she's gone". Thatcher had just resigned.


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## Chris70 (9 Aug 2022)

PDW125 said:


> If it is an unvented cylinder - ie one with no header tank and at mains pressure - it is not required. Get it turned off


How can I tell simply if it’s an invented cylinder? ‘Power Naturally’ designed and installed it. I’ve every reason to believe they’re competent.


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## Chris70 (9 Aug 2022)

Chris70 said:


> How can I tell simply if it’s an invented cylinder? ‘Power Naturally’ designed and installed it. I’ve every reason to believe they’re competent.


Err, unvented, not invented.


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## Phil Pascoe (9 Aug 2022)

Turn the taps on. If the hot and the cold come out at the same rate, it's probably unvented.
Turn the rising main off - if you've still got hot water it's vented.


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## Jacob (9 Aug 2022)

dickm said:


> Can't disagree with most of that, just that my experience of the VC one was that its thermal mass was useful IF running all the time, but even doing exactly what you say, it was a pig to get going for intermittent use.


Maybe a flue problem? It takes longer to get a woodburner going from cold if it's piped into an old masonry chimney rather than an insulated modern flue pipe. Sometimes pays to get a draught going by burning loose paper, cardboard, small kindling first.


dickm said:


> Don't know the Dowling stoves, but had read that welded sheet was inferior to CI.


Seems indestructible. Have only burnt wood, maybe coal would be too hot


dickm said:


> ..... he suddenly shot out of the car, waving his arms and shouting gleefully "She's gone, she's gone". Thatcher had just resigned.


I remember the feeling!


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## Phil Pascoe (9 Aug 2022)

Jacob said:


> Seems indestructible. Have only burnt wood, maybe coal would be too hot


It isn't. I burn anything that will go in mine. 


Dowling Stoves - Little Devil


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## Skydivermel (9 Aug 2022)

Phil Pascoe said:


> Turn the taps on. If the hot and the cold come out at the same rate, it's probably unvented.
> Turn the rising main off - if you've still got hot water it's vented.


What he said


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## Misterdog (9 Aug 2022)

Skydivermel said:


> I've been in the industry for 27 years. There are many factors to consider prior to making an informed decision. Don't listen to you mate down the pub who has watched a YouTube video on ASHP.



I installed a state of the art Ideal Logic condensing boiler some 7 years ago (a superb piece of engineering by the way).

The sales patter at the time told me that condensing boilers were 90/95% efficient as compared to my old Worcester Bosch 'standard' boiler at 70/80%.

What the sales/marketing patter did not inform me of was that in 'non condensing mode' the boiler was only operating at around 70/80% efficiency. Think car (ICE) on choke until the engine warms up.

One of the 'benefits' of this smart boiler is that it has a display showing a raft of information (I assume to be correct).


I have just accessed the data which informs me that during it's lifetime my condensing boiler has been in condensing mode for 55% of it's burn time........

So for nearly half the time it has been running, it has been at near the efficiency of my *old* boiler. efficiency wise.

'Wise sages' will tell me that I need weather compensation control,
larger radiators or to run the system 24/7 to get the return temperature down and increase the efficiency.

A good salesman can convince you of anything,It's their job 

I fitted WCC 2 months after I installed the boiler... so it is included in the stats provided above. 

So how much has my boiler change saved the planet ?
very little I suspect.

How much has boiler change saved me over the last 7 years .

Sod all basically - though it is a superb piece of engineering with useful diagnostic software, *I assume to be accurate.*

I have a friend who invested in an ASHP some 7 years ago it broke down, no one could fix it he so he fitted a condensing combi boiler. 


Beware the sales/ marketing/green claims is my advice.


Turn down your heating thermostat to a sensible level 17/19C
and wear an extra thermal layer or even a wooly hat if you really wish to 'save' the planet.

A 1 degree reduction on your heating stat =10% reduction in your heating bill. - ish.

All real life scenarios not from a mate down the pub 

Anyone wishing to give me £ 10/20 K I can 'promise' that you will be saving the planet and your wallet over the long term.
DM me for details.................


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## Misterdog (9 Aug 2022)

Skydivermel said:


> If Govt gave grants for the correct insulation then we could all run ASHP. BUT if insulating to a very high degree then we have the issue of moisture retention which leads to the necessity of the correct ventilation system for the property.



If only the government would give me £ 100 K I could do that.

Outrage.


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## Chris70 (10 Aug 2022)

Phil Pascoe said:


> Turn the taps on. If the hot and the cold come out at the same rate, it's probably unvented.
> Turn the rising main off - if you've still got hot water it's vented.


#Phil Pascoe Thanks!


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## deema (11 Aug 2022)

Thanks everyone, heat pumps are definitely now on the maybe one day pile.
What I was surprised by, because I hadn’t looked into it before is that oil has a much higher BTU/ litre than LPG, approximately 1.5 times. Price wise oil is usually close to lpg. No brainier which is the more economical to run. I’m on oil in my present house.


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## MikeJhn (4 Dec 2022)

We had oil central heating installed over thirty years ago and it's still on the same CI boiler, my Testo 327-1 gas analyser tells me I am running at 86% efficiency, think I will keep it.

Solid flint walls so no chance of insulting them.


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## Pedronicus (4 Dec 2022)

MikeJhn said:


> my Testo 327-1 gas analyser tells me I am running at 86% efficiency, think I will keep it.


With respect the analyser is showing the efficiency of combustion not the efficiency of heat transfer from the boiler to the heating system or from the heating system to the property both of which will be considerably lower.


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## MikeJhn (4 Dec 2022)

Perhaps so, but how else do you measure the efficiency of a Cast Iron boiler, I think the efficiency of combustion is close enough, temperature setting on the boiler and water temperature seem to correlate, as do flow and return temperatures that also indicate an efficient system.


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## Pedronicus (4 Dec 2022)

MikeJhn said:


> Perhaps so, but how else do you measure the efficiency of a Cast Iron boiler, I think the efficiency of combustion is close enough, temperature setting on the boiler and water temperature seem to correlate, as do flow and return temperatures that also indicate an efficient system.


From the data badge you read the input power and the output power. Those figures will give the efficiency that the manufacturers designed the boiler to work at. You will find that it is nowhere near the combustion efficiency of 86% which, as I have said, is not the same as the output efficiency of the boiler.


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## Spectric (4 Dec 2022)

I think it earns a massive efficiency rating just because it has delivered for thirty years, that makes it resource efficient unlike so many modern combi boilers that can become beyond economical repair after eight years. 

The solution to our energy crisis is to build houses with decent insulation and high thermal efficiency, yet we continue to just build these sub standard sheds because the shareholders want good returns. Again our problems come down to greed and not delivering for our future needs.


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## XTiffy (5 Dec 2022)

Spectric, If what you say is true (sub-standard sheds), then that is a failure of Building Control. I have built four houses in the last 18 years and the insulation requirements have increased massively. Such that cavity width has increased above the often standard 100mm or four inch in the past, to enable greater thickness of insulation. Air tightness regs. have likewise increased. Condensation will be the next big bad wolf! Where the problem lies is developers using cheap barely trained tradesmen for building. I pity the poor buyers who face long snagging lists due to incompetent tradesmen.


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## rogxwhit (5 Dec 2022)

XTiffy said:


> developers using cheap barely trained tradesmen for building


Indeed, and there are two aspects in fact - one is training and the other is motivation. I mean personal motivation to understand the task and do it well. 

Insulation is undoubtedly key but can be installed badly so that it won't perform to its potential. It's great merit is that once installed it is passive and should last the life of the building without further input. In contrast, all high-tech heat sources - boilers, heat pumps, pellet stoves, etc, have a quite modest life expectancy.


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## MikeJhn (5 Dec 2022)

Pedronicus said:


> From the data badge you read the input power and the output power. Those figures will give the efficiency that the manufacturers designed the boiler to work at. You will find that it is nowhere near the combustion efficiency of 86% which, as I have said, is not the same as the output efficiency of the boiler.


Then how do you measure the output efficiency of a modern CH boiler on it's annual service, or is the manufacturers data just quoted as a matter of course?


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## Pedronicus (5 Dec 2022)

XTiffy said:


> that is a failure of Building Control.


Sadly most LBC departments are now outsourced to private companies who tend to be subject to "commercial pressures"!


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## D_W (6 Dec 2022)

deema said:


> Thanks everyone, heat pumps are definitely now on the maybe one day pile.
> What I was surprised by, because I hadn’t looked into it before is that oil has a much higher BTU/ litre than LPG, approximately 1.5 times. Price wise oil is usually close to lpg. No brainier which is the more economical to run. I’m on oil in my present house.



LPG and propane here are generally a little more expensive per btu than oil, too, but they do have some side benefits:
- almost nothing to clean in a furnace
- if you want a gaslog fireplace, you can run that, too, which turns out to be relatively efficient if you're living alone and can heat a small area to it and turn down the rest of the house.

GSHP is replacing oil and propane an ASHP here pretty quickly. ASHP is the cheap option in a lot of new construction. Your boilers may be different than the typical oil boilers here, but the oil here is diesel #2 and furnaces generally need an annual service/cleaning and are really gummed up by then. Not hard to do on your own if you have access to the proper brushes and convince the service guy to let you watch a round. But filthy. 

I've had a gas furnace in the house for going on 17 years. It was here for 23 years before I got here and is still probably very close to its efficiency rating (80%) and it has been checked four times, but never needed any service. Because the A/C that it's mated to uses an older refrigerant that would now cost $1500 to charge, it's going to have to go this spring. I'm not easily convinced that it wouldn't continue to run longer than a new furnace will last, but the A/C is running hard enough to cost an extra $150 a month in electricity with dwindling coolant. 

GSHP costs about the same as gas for heat here, the units are complicated (electronically) and service is expensive of one of the boards has problems (FIL and BIL have units that each have four separate PCBs in them and the service guys have trouble diagnosing them and getting the right parts. it sounds like they try to be all things to all people all the time with complex functionality.). In the summer, though, they are super efficient and most of the places where they're popular are folks off the gas grid. Oil and propane probably cost double on average vs. ASHP and piped natural gas.


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