HI, Looking for a starting point on this and have read several discussions but wanted to expand a bit.
I have an old farmhouse in central France, c 200sqm across two floors.
last upgraded c1930 so needs a complete workover which means i am starting with a clean slate.
There is a very old woodburner but if a am to use the burner as a heat source for a heating or hot water system then this will need replacing with a new one.
What i am trying to get a grasp of is what is the optimum in both energy efficiency and cost efficiency at providing mainly hot water in the summer and heating and hot water in the winter.
Obviously, number one is to retain as much of the heat generated as possible and so i have got in new double glazed windows, i have silicon sealed all the gaps in the upstairs floor/downstairs ceiling. I will next be insulating the roof upstairs.
I have a modern very well insulated balon at the house - if i’m living there myself and showering several times a day then this only needs to go on every 3 days.
What i am looking at are two things
- hot water in the summer - favored options in terms of return on cost appear to be a second heat exchange balon - i have been told that this type of old balon can be sourced and installed cheaply? - and link this as the main input into the existing balon. Into the heat exchanger i can then do a simple hosepipe in the sunshine solar heating system which will pre heat water in the heat exchanger before going into the electrically heated balon for top up heating.
- hot water in the winter - I Can also use the same pipes and input system to build a compost pile heater for the winter and so get the same preheating effect for free over the winter.
The next challenge is to get a heating system in and this is where i am looking for advice.
options
- Use the current balon as the heat source for a radiator system so this will be green energy topped up by mains electric
- replace the wood burner and use this as an additional source of input into the system above
- replace the wood burner and install a dedicated system using the new one as the source of heat for the new heating system, this can either be a wet system or a dry air system
- jut use plug in electric heaters and forget about a wood burner at all
all thoughts opinions and links to people who know a lot more than I do on this are welcome
cheers
Bear
There Ă quite a few questions:
Are you replacing the ground floors?
Do you have town gas?
Are you able to add solar panels?
Are you considering insulating the walls with dry lining?
@bear69
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cheers.
HI Mat,
thanks for your reply - yes a few questions as i’m looking to start in the right way so i don’t have to undo stuff in the future and when you start to look at one issue, several others which can be linked raise their head…
but to answer yours
-
am i replacing the ground floors - no, these concrete and in good condition. I am looking in the future to lay a suspended wooden floor on top of this so there will be space for water pipes and electrics to pass underneath - not sure i will have the clearance for hot air ducts
-
do i have town gas? no
-
am i able to add solar panels? Physically yes, and i believe there would be no issues with permissions either. thing with solar panels though is I understand them to be expensive to buy and install, require maintenance and replacing and, if used for electricity generation, not that efficient and if used for hot water then not very cost efficient vs just putting a length of garden hose on the roof so, while taking “free” energy from the sun, they are actually not massively cost effective nor particularly green due to manufacturing process. Happy to hear if I am wrong about this though.
am i considering lining the walls - considering it yes but not sure of the benefits vs the effort. The walls are 600mm+thick of stone. in the summer the inside of the walls facing the south sun all day remain cool to the touch so they are obviously a good level of insulation in themselves. Dry lining will add to this but i feel if i do go that route it will be as much as a cheaper way to get a good decorative finish - as the current plaster will need to come off - than a necessary part of heat insulation. again happy to hear if someone thinks this is incorrect.
cheers
Alan
It sounds like underfloor heating will not be effective as you would need to insulate the floor also and there wouldn’t be space.
As no town gas, the bug bottled gas would be an option but expensive.
Do you have access to wood on your land?
You could consider a wood chip boiler - expensive but it may be viable in the long run.
Tricky choices.
Whichever way you heat your house… I would suggest thorough insulation throughout and double glazing to high standards … to ensure that the heat stays where you want it.
Double glazing and silicone tubed into every nook and cranny is not going to have a positive result on it’s own.
As you say the goal is heat retention and the ultimate can only be achieved by applying modern methods which is possible without spoiling the character of the house.
Floors, replace them with suitably calculated insulation beneath the concrete finish.
Double glazing throughout, absolutely.
At least 40cm thickness of insulation in roofspace and every other void possible.
Thick stone walls are a natural insulator but must be pointed inside and out, if they are less than 50 cm thick then consider adding insulation.
Insulate all pipework.
Insulate all internal floors and partition walls.
We had the opportunity of a blank canvas with our current house and gave it a complete renovation from the shell upwards and by doing all of the above and more the central heating system that is throughout the house is never used on the first floor which maintains a near constant temperature of 18 to 20 degrees.
Our principal fuel for winter/ 6 months of the year is oak for which we pay about 500 euros and it provides all the heat and hot water anyone could need.
Hot water in summer months is via off peak electric which heats the water in our super insulated water storage tank which will stay hot for 5 days without reheating.
The answer to efficiency is insulation and then more insulation and done correctly, and to the optimum, you will reap the benefits.
I renovated our home with my professional builders hat on but the information required to correctly insulate your home to achieve the best results is out there on Google, YouTube et al.
Insulate, insulate, insulate.
There are programmes with titles like A Place in the Sun which suggest that France is exactly that, yes it is in the summer but at other times much less so and if you are sitting snuggly in your super insulated home you will be cosy and warm throughout the year.
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Personally, I’m ever cautious about the notion of holding hot water in one of the modern balons for days on end without maintaining the temperature at its design level.
There is a school of thought about the risks of Legionella bacteria which is killed off by maintaining the water at the correct temperature.
Using Electric correctly from a good modern installation to current norms, it should be possible to use a very minimum of electric to just top up the balon at the creuse hours rate automatically switched by the supplier. Nothing more to do.
In my humble (and non professional opinion) this represents best safety sense since legionella is a killer and the risks grow exponentially the older you get.
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Graham, I was not suggesting that the water is stored for days on end without being held at the correct temperature but merely demonstrating the insulation value of the storage vessel. The water is maintained at the correct temperature either by the wood burner or by off peak electricity on a daily basis.
but some people do @JohnBoy so hence the reason for my cautionary note…
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Hi Matt,
thanks again for the suggestions.
I have considered underfloor heating as i do have plenty of headspace to play with downstairs, I have electrical units into the new bathroom which were cheap to buy and, as we had to dig up the floor to sort out the pipes, almost no extra cost to install. they work well in the small enclosed space under a tiled floor but not convinced that electrical ones would be a cost effective solution for the rest of the ground floor as I would then have to go through redoing a hard floor and potentially tiling over the top - which i know is traditional - but i prefer to look at a wooden floor downstairs which would not have the heat transference properties required for underfloor heating.
I do have some wood on the land and i have plenty of young oak coming up, but maybe these would be good as fuel in my kids lifetime, but probably not mine 
Woodchip boiler is an interesting option. I am though considering what can I use that I already have - so as to reduce set-up costs and also not sure where I would have the space for this.
again, thanks for the suggestions as they are all helping clarify the issues in my mind
alan
HI Stella,
thanks for the reply.
yes, I agree, Insulation is the key to heat efficiency. The goal i am looking towards is how to get carbon neutral or even negative in my energy consumption for the house so the more I retain the less I have to look to produce which fits the bill. Hence initial work on the house has all been in sealing off gaps, installing new double-glazed windows, installing modern efficient balon etc
The key now is how do I get to produce the heat required, which is why i was looking at the DIY solar options, as well as compost generated heat - this is actually quite amazing and worth a few minutes of anyone’s time to watch
and as I am looking to grow my own food then the compost pile will be developed anyway and so the energy produced will be genuinely free - and carbon free - heat.
Just looking at taking this all to the next step but realising that while the woodburner option feels free, to do this properly requires significant initial set up costs and i’m not convinced that the ongoing costs are significantly lower than using electrical heating
cheers
Alan
HI John.
thanks for the detailed response - good to hear from someone who has gone through this and done it properly
I’ll check out the details on youtube etc as you suggest. a couple of things though if you have the time to expand or send decent links
If you have the time/inclination can you let me know how your CH system fits together? from what you say, you have a wood-burner of some sort (furnace or in-room stove?) which is the main source of heat in the winter, with the electrical coil in the water tank providing hot water for the summer months. This appears to be similar to how my thinking was going and I’m just looking at the most efficient way of integrating these together, along with the other sources of heat i am considering. do you have the heat from the burner going into the hot water tank which is linked to the CH system?
thanks
Alan
HI Graham,
thanks for taking the time to comment. John actually said the same as i was going to re water storage. I turned mine off as an experiment to test both the capacity and insulation but i agree, having it on every night to just top up the temperature is probably the best idea if the tank is well insulated so you only lose the energy through the walls very slowly.
cheers
Alan
I recommend insulation of the stone walls… even if they are really thick, they will absorb whatever heat they find… so why use a system to heat more than you need to.
There will be some who agree and some who disagree… such is life.
And I’m going to be the first person to disagree. If your stone house is a permanent home your stone walls will act as a heat store. The room might take a bit longer to heat up at first, early in the winter, but as time goes on the heat retained in your walls has a very positive effect. A stone house that keeps cool in the summer by keeping the heat of the sun out will also keep the heat of a heating system in. Then we get onto the topic of the different aesthetics of having a beautiful pierre apparente walled salon or a featureless plasterboard box. 
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I agree with @anon14704272
Before we moved to the Charente and built a new wooden framed house, we looked at a property in the Allier renovated by a Dutch couple.
They used oil central heating and never turned it off during the winter months. It was on 24/7 very low in the background with the radiators touchable without the toucher getting burnt fingers.
His theory, which I subscribe to, was that the stone walls created a heat store releasing heat back into the room. People who turn off the heating during the day while they are out are subscribing to a false economy since when they return, they turn the heating up to attempt to get the place warm again.
It doesn’t work.
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