Allotment Gardening Advice Help Chat
Smallhold Farming and Rural Living => Property, Buildings, Equipment and Alternative Energy => Topic started by: Spana on February 09, 2011, 14:42
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Over the last few months we've been talking to several companies and getting quotes for a 4kWp photovoltaic system for the house. We would also like to get rid of our oil fired boiler.
The company we favour the most has been to do a site survey for the panels and recommends changing our old oil fired boiler for an air source heat pump.
On paper the panels make sense financially but i cant get my head round the air source heat pump. OH is really keen on both.
We don't know anyone who has either the photovoltaic panels or an air source heat pump but the company say they have installed both systems to customers who would be willing to let us have a look.
I know some of you guys are interested in this sort of thing and wondered what you thought.
I'd be really interested in anything you have to say good or bad about both systems.
Thanks
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I'm dead keen on installing a very minor 12volt solar panel system in our home. We tend to get depressingly frequent power outages here, and it would be interesting to see what we could run and for how long on a small scale system.
As for the air source heat pump, I'm interested but know very little about them. I'd say go and have a look at the ones installed, and see how the owners home/ lifestyle compares to yours. I'd love to hear how the people get on with it, and whether they find they need to have any other type of supplementary heating, and if so, what-and for how long?
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I don't think PV panels make much sense ecologically in the UK but with the feed in tarrifs they may well make economic sense.
Air source heat pumps.. probably better than oil (or LPG) but as you've got land, what about a ground source? Much more consistent especially in really cold weather (OK, I know you're in the warm bit)
Watch out for noise with an air source pump. You may need to house the outside bit to keep the noise down.
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Thanks Gwiz and John.
Gwiz, i'm not good with this 'lectric stuff. Do you intend to store electricity in batteries?
John, my John-OH- wont consider a ground source heat pump altho I think it would be a better system for radiators. We're going to have a look at some air source heat pumps working and apparently the government will be making some sort of statement about them in April and we've been advised to wait and see what thats about before making any decision. I'm also worried about noise and efficiency. We had one when our girls were children to heat a swimming pool and i was never impressed but that was 30 years ago and I'm thinking they must be much improved now.
I quite fancy the PV panels, we have a good unshaded south facing site to put them. Is it lack of day light that makes you say they dont make ecologically sense in the uk or something else?
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Well ground source pumps are about 4:1 whereas air source are 3:1 but ground source costs more to install - so you pays yer money and yer takes yer choice.
With our northern latitude, amount of cloud cover etc PV doesn't make a lot of sense in terms of power generated to cost incurred. However, the lack of joined up thinking from the government means you can get crazy amounts of money from the feed in tariff. So if you've the money to invest, better than anything else from a financial viewpoint.
Wind power can make eco sense, depending on your location.
With heatpumps the higher the temperature you want to have inside, the lower the efficiency. They're great for underfloor heating where you are after water temps. around 20 but if you're running with radiators which usually run at 50 or 60 not so good. What you can do is use over-sized radiators or those electric fans (very low consumption) that pull the heat out from the radiator and use those, turning down the water temp.
Also, run for longer at lower temps to keep the house warm rather than the burn / stop system fossil fuel fired boilers use.
How come your John is so anti ground source?
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How come your John is so anti ground source?
Well, I've just asked him that and he says hes been sitting thinking about it and now thinks it might be better. :wacko:
if you've the money to invest, better than anything else from a financial viewpoint.
It seems crazy to me and i keeping looking for the catch. Thats one of the reasons i asked here ::)
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There's always a chance the gov. reneges on the deal in a few years I suppose.
If you've got the room, trees. Willow for chipping into a boiler etc. Efficient, truly green but I don't think you get a grant
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On our small scale effort, the generated electric would be stored in batteries ready for use when the power fails (often)We wouldn't need to use too many batteries as we are only talking about a need for up to a few hours at a time. One side of our roof faces due south, so would accommodate some small panels quite well.
As an aside, at work we got permission to erect a rather large wind turbine, however, after looking more into the figures, it wouldn't have been cost effective to go ahead with it. We are looking at pv panels though, which produce electric even when it is cloudy (not as much, but enough to be worth while from a PR, feed in tariff point of view) It would certainly help to drop our violently expensive electric bills.
I must find out today if we are going ahead with the plan, it seems to have gone a bit quiet on the news front.......
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I've always been interested in alternative power as it was known but have to say that self-generating is not the best use of government funding. Combined heat and power in the cities would save far more CO2 and increased efficiency heating like ground source heat pumps on grant would make sense. Plus yet more insulation.
The trouble is most of us don't want to spend to save money in the future. Put £100 in a bank and maybe you get £2 interest in a year. Put £100 into insulation and it might be £10 or even £50 off the fuel bills but people don't see a line on the gas bill saying "Extra Insulation Saving"
I've seen in Norway and Austria just how efficient insulation can be - minus 20 outside, plus 20 inside and just a teeny tiny radiator in the room. Thanks to treble glazing, 2 feet thick walls filled with insulation etc
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wandering off topic slightly, but our old housing stock (I'm thinking victorian terrace here) cannot easily be insulated to those high standards, and that's a huge problem for the future :(
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One tip - if you've a high ceiling you can use a fan to drive the heat back down. It's amazing how much difference in temperature there is at the top.
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"One tip - if you've a high ceiling you can use a fan to drive the heat back down."
I have always been puzzled about this. Surely by 'driving the heat back down' you simply speed up the convection currents so that the heat rises a little bit faster. You cannot gain anything overall.
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Ah, but rather than having all the hot air at the top, the fan will circulate the hot air giving a more even temperature over-all.
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I've seen an old carpet inner tube (from carpet shop) with a fan (DIY store around £10) fitted to the bottom in an old flat with 10' ceiling. It was like having a fan heater in the room. I'm sure a neater job, painted etc wouldn't look bad either. The one I saw was a bit of a duct tape nightmare but it proved the concept.
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Gillie, the fans rotate slowly, never fast. The idea is to move the air, not spin it. Every time I start up my wood burner, I switch on my ceiling fan which is set to low, and the heat can easily move to most rooms. Now only if it went around corners into the bedrooms, I'd be SO happy ::)
Last fall we finally finished doing a heavy insulation of our attic. We packed 12" thick batts across the whole attic, over wood framing and everything except for the outer edges where we allowed air to enter the upper areas to prevent mold and moisture. We've noticed a big increase in warmth and that the furnace turns on less often. Normally we'd be into our 3rd tank of oil by now, but have only just gotten our 2nd tank, so yes, mega saving even doing the attic.
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Here are a couple of interesting videos if you're handy: Both are heating related.
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We have photovoltaic cells, we started using them in August, so just as the brighter summer days were coming to an end. We have been rather surprised at how little electricity has been generated on overcast days, of which you will have many more in the UK! Bright sunny days are fine and we make lots of electricity. We work on a different system here in that we pump all our electricity back into the grid, not just what we do not use, we gat about 3 times what we pay for it I think and we get paid once a year for what we have produced. It should pay for itself, we get a tax rebate which is almost half the cost.
We are keeping tabs on how much we use and make to see how it works out. Our electricity bills are high, probably because we heat our water with it as this is the normal way in France - we hope to go solar for that at some time too - good job we have a large roof!
I am not sure that if we were in the Uk that we would go photovoltaic, unless there are lots of government incentives.
We will also go down ground pump at some time, air source pumps are more popular here than the Uk as they do Air Con too - which may be a bonus even in the UK.
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My mum and sister both have heat pumps where pipes are buried in connected lengths underground. Both installed this system because they worried about rising winter heating costs. The real kicker, that most folk forget, is that heat pump systems are useless without electricity, which is skyrocketing everywhere. What they saved in furnace oil is now replaced by electrical costs, moreso because both of them had in-floor heating installed and it takes a lot of juice to constantly push the fluid around large areas. There's no way to disconnect the in-floor heating system as all floors were tiled or had hardwood flooring or concrete (in basement)
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We have been rather surprised at how little electricity has been generated on overcast days,
Reading the energy forums that's one of the down sides most mentioned. But most say the good days do compensate for the bad.
Something that does seem to make a difference is keeping them clean. This year a lot of people with them on their roof had them covered in snow for days on end. Ours will be mounted on the ground at the top of a bank so will be easier to keep clean, I hope. :unsure:
Another problem here seems to be getting your payments out of the company you sell to.
Junie, do you know what size system you have, do you keep daily records.
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What they saved in furnace oil is now replaced by electrical costs, moreso because both of them had in-floor heating installed and it takes a lot of juice to constantly push the fluid around large areas.
According to the government, heat pumps make sense if you're on oil or LPG heating (in the UK - the equation may be different in Canada)
They're a big investment though so a lot depends on you having the initial capital to invest.
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I've not heard of any heat pumps in Canada run on oil or LPG; the point was to get away from true fossil fuels.
As for costs, my mum paid over $10,000 for hers, my sister, in a bigger house, paid closer to $15,000. And that was about 10 or more years ago for both. You definitely need deep pockets for this.
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Hi, We don't keep daily records, but the equipment does keep some records, which I have just got the OH to show me how to get to. ???
On a cloudy dull day we will make about 1 kW hour
We had a bright sunny day last week ( from about 10am to 6pm)in which we made 8.4 kWhours
I have the monthly readings too here
August 222 kW hours
September 268 kW hours
October 200 kW hours
November 90 kW hours
December 100 kW hours
January 122 kW hours
Our system has 12 panels ( 1m x 1.5m multicrystaline).
We face due South.
We live about 50 km north of Toulouse.
We do have a quite a shallow roof, which does not make it optimal for winter use, but should really benefit in the summer, if you are putting it on the ground, it may be worth seeing about being able to adjust them them for winter and summer time. ?My OH also mentioned reflectors which could extend the optimal time for your cells.
You will also need quite a bit of room for all the 'boxes' we will have to make a special cupboard for ours as they are in the hall. I will post a photo later to show you what we have.
As far as our figures go
We very roughly paid 22000€
Will get €9600 back in tax rebate
The rest was a very low interest loan which is supported by government.
We receive 56 cents per kWh for every one produced
We pay 6 and 9 cents depending on time of day, so we get a normal bill and a yearly payment for what is put into the grid.
OH has worked out that we need to make 231 kWh hours per month to break even for the installation and cost of the system. That is not taking into account reducing the electricity bill at all.
We have talked about air source, but see them as quite inefficient compared to the ground source, although much cheaper to install. the thinking is that, when you want the house warm, the source air is very cold, when you want to cooler inside, the source air is hot, so there is always a large change in temperature required, which could be as much as 30 degrees going by last winter in the UK. This is surely going to cost quite a lot in power to get that heat. With Ground source the ground maintains a roughly constant temperature of between 10-16 dregrees, so the change needed in temperature is far less and therefore less energy will be required.
I hope this has been of some help. Any more questions just ask and I will try to help!
June
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there are a number of PV installations, ground and air pumps installed in the village through the local low carbon group. There is no gas in the village, so the alternative fuel to on grid electricity is (gulp) oil or wood burning stoves.
the received wisdom seems to be that PVs are great on an unshaded south facing roof and generate more than enough for the household and to sell to pay off the investment in a few (3 - 5 are generally mentioned) years. However - there are a lot of sales organisations that will still sell you them for SW or SE facing roofs where they are a lot less effective, and you might be better just going for a cheaper water heating panel and forget the electricity generation.
The village wisdom on ground source pumps is only do it if you were going to remodel the garden anyway! Air source on the other hand, I know 3 installations where the owners have been very pleasantly surprised at the amount of heat generated and the lack of fuss. No complaints about noise. In two of the cases they have PV generation so they are pretty self contained.
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I've not heard of any heat pumps in Canada run on oil or LPG; the point was to get away from true fossil fuels.
The point John was making is that in the UK it makes sense to change from oil/LPG to an electrically powered heat pump. This is due to the cost of oil/LPG, delivery and the space to store oil/LPG.
Also in terms of carbon, in the UK gas is roughly three times cleaner than mains electricity (this is due to the mix of fuels used to produce UK mains electricty - still a lot of coal power stations as well as gas, some biomass, some nuclear and a small proportion of Hydro (less than 10% last time I looked, mostly in Scotland)) which means that any electrically powered heating system needs to be at least 3 times as efficient - otherwise you may as well use gas.
Most air source heat pumps have a seasonal efficiency that is worse than this even though they state COP's (co-efficient of performance - the amount of heat/cooling you get from something for evey 1 kW of input electricity)of 3-8. There are a number of issues that affect the COP of heat pumps -
1. heating medium - standard rads in your home are sized at a flow/return temp of 80/60 degrees C and most operate at 82/71. A heat pump will only give you around about 45 degrees C flow temp. You can increase this temperature but the higher you go the lower the COP. At 45 C the COP of the heat pump maybe 3 or 4 at 55C it will be less than 2. At 35 degrees it may well be 4or 5 - happy days. BUT my rads are sized at 80 - so i'm not getting the required heat ouput! Underfloor heating generally operates at 45/25 f/r temperature (or less) and so is perfect.
2. What is providing your domestic hot water? If your storing DHW (in a cylinder for example)you need to do this above 55 C due to Legionella. So a heat pump could do this but it would but the COP is low (less than 2 remember) it may also take a while to heat the water. A lot of these systems have an immersion top up for the DHW cylinder - so I'm back to using grid electricity to heat my water (which is 3 times dirtier than Gas).
3. Is the manufacturer stating seasonal efficiency? In the winter the heat pump will need to use energy to defrost the external coil - the COP obviously drops in this case.
So if I'm using grid electricity to heat my water, i'm not saving carbon and it's more expensive than gas (roughly 10-12 p/kWh compared to 3.5-4p/kwh).
So - if your on gas your probably better off both financially and in terms of carbon by sticking to gas or going for something truly green (if there is such a thing......).
If your on oil/LPG then heat pumps are for you! All the above applies to GSHP as well although they generally have a better COP than ASHP. It also applies to the UK market other countries have different tariffs and energy mixes.
If we clean up our grid generated electricity then heat pumps start to make sense from and environmental point of view (which is why they use them in scandinavia a lot where their grid electricity is all from hydro/biomass).
Going on far too long now!
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the received wisdom seems to be that PVs are great on an unshaded south facing roof and generate more than enough for the household and to sell to pay off the investment in a few (3 - 5 are generally mentioned) years. However - there are a lot of sales organisations that will still sell you them for SW or SE facing roofs where they are a lot less effective, and you might be better just going for a cheaper water heating panel and forget the electricity generation.
3-5 years is optimistic - before the introduction of the Feed in Tariff (FIT), PV used to take 70 years to payback. Now, with the FIT I would say 11-12 years is about right - prices are coming down all the time though and so this will get shorter.
As to orientation -
The perfect orientation is due south with a 35 (ish) degree tilt (again, this applies to the uk - as latitude changes so does the optimum orientation). You get the maximum direct exposure and therefore maxium output (although if the panel gets too warm then efficiency drops off.......lol).
You should be able to generate approximately 800kWh of electiricty a year per installed kW in the south of the UK. This is the yearly average - most of this figure is achieved in the summer months.
So this will save you the most money (decreases payback period) and the most carbon.
You will still see some generation if you install the panels se/sw - probably 90% of this. If you install panels east/west you will achieve maybe 60% (probably slightly less) and if north maybe 20%. This smaller amount of generation still offsets grid electricity and so still saves carbon. It will of course take longer to payback - but if your interested in saving carbon and dont have a south facing roof then you can still do something.
You need to remember that the output will drop as the panels get dirtier and that the silicon degrades over time and so output will drop over the life of the panel anyway - there is no exact numbers to this that I am aware of but it could be as much as 5% every 5-10 years - just best guesses as nobody has had a panel installed over 20 years and bothered to check this yet!
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Junie, Madcat and Bluedave. Brilliant info. :happy:
Thank you all for taking the time and trouble to post it. I've printed it all off for OH to read. :happy:
I had very mixed feelings at first but getting quite excited about it all now. 8)
We're going to see some air/ground source heat pumps working and will make a decision on which to go for after, but have decided to invest in the PV panels to get us started. We were hoping to have them in place for this summer but a lot depends on how quickly the planners move as we need planning permission even tho its only a domestic system.
Junie, if you can get a photo of the meter boxes I'd be interested to see it. :) thanks
The company say there will be very little mess in the house, can i believe them :unsure:
How was it for you :D
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Spana, Here are the photos
the first is the cells on the roof, we also had to have a white casing down the front of the house to go to the boxes ( you will not have that problem though! )
the second in the meter boxes etc, It is only those on the wall in front of you, not those on the left hand wall, which are our original meter and one of our rcb's.. One thing I did forget to mention was that it does make a buzzing noise when it is working, it was annoying at first, but we do not really notice it now!
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Thanks Junie, its a lot more stuff than i thought it would be :blink: but it does look quite neat :)
Your house looks beautifully french :)
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Hi forgot to say, there was no real mess in the house as everything was done on the outside in conduit, only one wire through the wall - which took sometime!!
Our house is certainly a classic looking farmhouse for this area! :)
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TYour house looks beautifully french :)
I agree there :D
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We were hoping to have them in place for this summer but a lot depends on how quickly the planners move as we need planning permission even tho its only a domestic system.
Do you live in a conservation area? If not then you shouldn't require planning permission or it should be a formality. There was some legislation last year or the year before to make it easier to install domestic size systems - I can try and dig it out for you if you like.
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Do you live in a conservation area? If not then you shouldn't require planning permission or it should be a formality. There was some legislation last year or the year before to make it easier to install domestic size systems - I can try and dig it out for you if you like.
yes please, if you can find it easily. Thanks :)
We didn't think we would need it at first but after reading all the info from the planners it seems that we do. Its because they are being mounted on the ground not on the roof. She did say there shouldn't be a problem but its all extra expense.
The site is unshaded, direct south at the top of a bank and can't be seen by anyone. Planning seems unnecessary to me, but there you go :D
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oh sorry, missed that bit. You will need planning on the ground - change of use - still should be a formality unless you've got something odd in your deeds or it's agricultural land.
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There are some advantages to mounting the panels on the ground . They should be easier to keep clean, no scaffolding costs and it appears the fire brigade are reluctant to attend a house fire where the house has PV panels on the roof :blink: ::)
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Our local planners (in a conservation area) are great :) ... they really try to help. Actually, that is true of most things (no, I'm not related to one and I dont have a planning application in progress), but particularly with green agenda stuff. Planners are humans after all - they just have daft rules that they are instructed to follow!
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1) PV cells have about 10% efficiency, so use that electricity for heating is ummm "not optimal" :nowink:
2) solar water panels for heating will be more efficient
3) heatpump(air feeded exterior unit) working well when outside temperature above 0, but depends on coolant
4) proper insulation and glazing is most efficient to cut out bills
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4) proper insulation and glazing is most efficient to cut out bills
It's always far more cost-efficient in terms of carbon reduction and, therefore, green to save energy rather than generate it although the feed in tariffs have distorted the economics so it might not make the same financial sense
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I'm dead keen on installing a very minor 12volt solar panel system in our home. We tend to get depressingly frequent power outages here, and it would be interesting to see what we could run and for how long on a small scale system.
As for the air source heat pump, I'm interested but know very little about them. I'd say go and have a look at the ones installed, and see how the owners home/ lifestyle compares to yours. I'd love to hear how the people get on with it, and whether they find they need to have any other type of supplementary heating, and if so, what-and for how long?
Think about a real and cheap alternative :- a generator. 2.6 kw generator selling in Aldi or Lidll can't remember which £170. Theres your lights computer telly and a microwave sorted in one go. Probably your central heating (pump etc)
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4) proper insulation and glazing is most efficient to cut out bills
It's always far more cost-efficient in terms of carbon reduction and, therefore, green to save energy rather than generate it although the feed in tariffs have distorted the economics so it might not make the same financial sense
I am afraid for a lot of people carbon reduction is all about conspicuous consumption IE look what I am doing for the environment when in reality they have taken no account of the cost to the environment (in terms of carbon creation) of creating for instance wind farms and solar panels. Is it sensibly for instance to reduce carbon by a ton a year and create a 100 tons doing it? With a device which will last only 20 years? We are at the moment paying out 40p a KWh for renewable energy and charging 10p a KWh or less to the consumer. That alones says a lot about just how environmentally inefficient some if not most renewable energy sources are. Never mind the future for electricity prices??
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JohnB - that is very well put! The real reason I would look at PV or a turbine is to use it as a retirement investment based on the FIT. Our REAL carbon savings come from mundane, boring loft insulation etc.
Eventually our investment of time, effort and a little money in trees will provide us with free fuel but that's not a route open to people without a lot of land.
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JohnB - that is very well put! The real reason I would look at PV or a turbine is to use it as a retirement investment based on the FIT. Our REAL carbon savings come from mundane, boring loft insulation etc.
Eventually our investment of time, effort and a little money in trees will provide us with free fuel but that's not a route open to people without a lot of land.
Remember what I said about the new roof turbines? the article was in the Sunday Times. Also I have my doubts that they will continue to pay 40p for something they can only sell for 10p Morover there is nothing to stop them changing the amount they pay in the futore unless there is a specific contract. I read they have reduced the amount they are paying to some renewable energy comapanies although the articles was not very specific. You could consider coming off grid if you could store the electric. A farmer In Lincolnshire had a new farmhouse built and all estimates for bringing electric to him were higher than having a large wind turbine and batteries (£30,000). He did live on the flat part and obviously he could not sell the electric.
Fire wood look at coppicing to get the wood quicker and to save splitting it.
I have the required amount of Insulation which I think is 10" or 12" is that right? Either way I took up a bargain offer a year ago of 170mm insulation at a £1 a roll. It is either a double or treble roll depending on the width of your joists. My neighbour said i shouldn't lay it as the benefits are minimal and it can course condensation. What do you think/know? espcialy on the increased insulation value or lack of it. If it is of minimal benfit or and courses condensation I would rather give it away, what do you reckon?
PS my neighbour is a builder.
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I'm well aware that rooftop turbines are not a good idea domestically, we've got some windswept fields facing to the prevailing wind so was thinking of a 15Kw installation. First stage is to erect a tower and measure the wind for a year.
There's a lot to consider beyond feasibility; - planning permission, lifespan and reliability of equipment and 'will the government stick to the deal'
Some years back I did the calculations on insulation using the U values and all that. There is a law of diminishing returns. the recommended depth of loft insulation has grown from 4" to 6" to 12" as the price of energy has risen. Assuming it is, as threatened, going to jump again, it seems reasonable to assume greater depth will become recommended shortly after.
As for the condensation, not heard this. Assuming the roof isn't leaking and the ventilation into the loft is as required, I don't see it being a problem. I'd look around on some building forums or seek advice from energy saving trust if it's a concern. We do have some good builders on this forum if they care to comment, it would be appreciated.
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When first electric lights appeared, "candle kings" did lot of things to kill invention. ???
When internal combustion engines appeared, it was epoche of steam machines..... ???
It's time to go solar now. When manufacturing will pass "critical mass" panels will be cheap as chips. Do you remember prices on the first cellphones? :D
Another thing is that equipment is little bit overcharged - blablabla, hi-tec, blablabla, qualified engineers and installators.... But that guys doubling the price, just by connecting wires between factory made boxes following manual :blush:
One more point is to use energy saving bulbs and LED bulbs
P.S. i have one crazy project in my mind how to build solar PV farm almost free, but it will take a bit time
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Condensation will occur if there is not adequate ventilation in a building fabric designed to be ventilated (i.e. cold roof construction or cavity walls). This is why you should be careful of blocking up air vents/bricks in old Victorian buildings for example as they were designed in to stop condensation occuring within the building construction.
Under current building regulations the level of insulation is so great that they are now looking at reducing things like thermal bridging and air permeability as these have a much larger impact on heat losses then adding more insulation (i.e. John's point about diminishing returns).
Buildings are now becoming so well insulated and air tight that the next problem is adequate ventilation, condensation problems and summer overheating. I think in new build dwellings we have gone as far as we can with building fabric. The next challenge is fuel mix/type and decarbonising the grid (nuclear anyone.......).
Our new build stock is so well regulated that it uses very little energy. The government should look at the existing stock and use some of the 'renewable band wagon' money for improving the insulation levels in older stock.
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The government should look at the existing stock and use some of the 'renewable band wagon' money for improving the insulation levels in older stock.
something I've been saying for a long while.
If fuel keeps rising in price as quickly as it has recently, all the old houses will be unsaleable.
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Years ago there was a study that reckoned improving insulation would create more jobs per pound spent than new power stations to provide energy. Seems to me we could knock back the unemployment levels a bit by investing in insulation as a nation.
I had a chat with our builder (they're doing some work on the house) about extra loft insulation and he said condensation can be a problem if there is inadequate ventilation in the loft space.
Since they're re-rendering the gable end of the house we also talked about external insulation. He said the local councils had been doing a lot of it but problems were showing up as the underlying insulation was moving and causing the render applied over it to crack. Basically he would do it if we wanted but not guarantee it.
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A big problem to look out for with external/internal insulation applied to exisitng walls is interstitial condensation. This is caused when 2 layers of insulation are introduced into a property with another layer of material between them and no ventilation (i.e. a brick/block cavity wall that is insulated in the cavity which then has a layer of insulation introduced externally or internally leaving) . Water vapour will condense between the layers rendering the insulation worthless and/or causing internal damage/damp.
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Our walls are stone & rubble. They built two dry stone walls and filled in between them with rubble and sub-soil. Not exactly energy efficient or waterproof. DPC? Don't make me laugh!
When I get chance, I'll do a cost benefit calculation on internal insulation of that wall. I suspect it won't make economic sense.