Installing a puit canadien and double flux system

You might have read my blogs or heard me refer to installing a puit canadien and double flux as part of our extreme eco-renovation (other names include, mad crazy English people's renovation, what on earth are they doing now renovation...)

So What is a puit canadien or canadian well, sometimes referred to as a puit provencale?

Well it's a type of renewable energy which provides both heating cooling in conjunction with a Double Flux (mechanical heat recovery and ventilation system in the UK). The system we are going to be using is by Helios. The thermal study was conducted by Fiabitat. What we are installing is a ground to brine heat exchanger which increases the efficiency of the Double Flux.

So what is a Double Flux?

Well it is a ventilation system heat recovery with enthalpy - eh? Well it takes in fresh air and in Winter preheats it before dispensing it around the house. The stale humid air is taken out but the smart part is that the heat generated in the house is not lost straight out of the house, it goes through a heat exchanger and passes the heat energy to the new cold air coming in then the stale stuffy air is released outside. The result is you have clean fresh air into the house without losing up to 90% of the heat (through opening windows or simple ventilation systems which extract hot air out to the cold outside).

Why? The humdifying function helps to keep the rooms at a healthy and comfortable climate without the need for additional energy i.e. air conditioning, humidifier units etc.

As you can see below, the fresh air is piped into each living room/bedroom in the house and spoiled air from bathrooms, toilet and kitchen is taken each room and passed through the double flux to retain the heat calories before expelling the exhaust air.

The Puit canadien is an underground geothermal loop system which further supplements this and should save even more energy and money as it pre-heats the air before it comes in without any additional energy being required.

This system uses the fact that the temperature below ground is relatively constant throughout the year. Our pipes are laid at 2.5m deep and 1.2m below the ground level.

Firstly a huge hole the size of a swimming pool is dug and prepped:

Then the tube is laid in

They are covered with sand and geotextile (the blue mesh to warn you not to dig into the tubes by accident in the future)

then the earth was laid over and compacted

ready for the second layer.

and now this is what it looks like:

The pipes come through a long trough into what will be the new chaufferie:

This will eventually join up to the indoor kit:

and the Double Flux:

All this kit will sit in the new chaufferie, as well as the wood gasification boiler and AKVATerm tank for the solar thermal hot water. Its going to be interesting to see that lot going in as well as the many pipes which run all through the building taking the clean and stale air out again.

As I said it's an extreme eco-renovation. The plan is to spend the money on investing in the heating/cooling technology up front and then hopefully have little or almost no heating costs in the future.

What's the point of having all this in an old stone house? It wont work as old houses are leaky right? Well we are insulating the entire inside of our house in 8cm of chaux chanvre - lime and hemp wall insulation, building internal walls out of chanvribloc (hemp blocks) and we are fitting good quality windows and lots of roof insulation. This insulation is referred to as a thermic correction rather than making it completely air tight. The old building can still breathe (avoiding humidity problems) but it is well enough insulated not to lose precious energy.

This is just the start - the terrassement has been completed and now we move indoors. The new internal wall foundations were poured a couple of weeks ago and hopefully this is where we now start to see the house taking a new shape and a new life. Bring it on!

For anyone interested in this sort of thing...have a look at Fiabitat website - a mine of useful information, also I subscribe to 2 French magazines - been wonderful for improving my french and building knowledge - Natura & La Maison Ecologique

Hi Suzanne I am full of admiration for your courage in embarking on this massive project and really hope it all turns out as well as you hoped and doesn't run too far over budget. It certainly sounds cheap to run.

Bon courage.

@ Mike - we are lucky that we don't have any solid internal structural walls in the house - this was the WOW when we saw the garage open one day whilst walking past. It was like...WOW we can do whatever we we are creating all the new walls and the gaine techniques for passing the ducting. The main constraints we have are the barrel vaulted tiled ceiling which we want to keep exposed in part for the living room so ducting has to go above the dropped false ceiling over the kitchen area/utility rooms and the new structural stair casing from ground to top floor which we can't pass through. The ducting diagrams are fairly complex 75mm piping - I'm just hoping it all fits between the false ceilings and the new RSJs - according to archi plans it should be fine...but whatever goes to plan eh! It will be quite a few years before we get the upper floor ceilings we should get to see some of the effectiveness on the lower floors first. Fingers crossed!

ah Vic - I just took them out of the report - but yes very funny they are to the cent. I will be going back to Mr Thermo if they are a cent out...ha ha.

@ Mike - they claim up to 90% efficiency on the KWL EC 500 Pro.

We intend to insulate the pipework and are running all pipes in purpose built 'gaine technique's' which will also be insulated with chaux chanvre.

re: hole - yes many people were shocked when we filled the whole back in again...that came after the initial shock of us wiping the whole garden was a jungle before. We may have a pool in the future but that will be long after the PVs are on the roof...(pop up paddling pool is looking like a pretty good option though)

@ Michael Blackmore - just to clarify - we're not putting in a GSHP - it's a canadien well. From my proposed figures the cost for running the whole ventilation system is only expected to be 112 euro a year for both the Double Flux and the Puit Canadien. There is no large GSHP unit which I recall from the quotes I had received was quite a hefty price was for this reason we decided to go for the Wood Gasification boiler (to give us the heating for the UFH system) and the Puit Canadien which would give us some comfort cooling (not air conditioning) in Summer and free heating mid season.

I suspect we probably won't need to use the wood gasification boiler as much as we think we will but it depends on the year...this year was mild and we had central heating in the gite from Nov to April. I could have done with a woodburner in there too on the coldest days as sometimes it was a bit too nippy for my liking. Now however I would be grateful for air con...though we are very hopeful that the PC will give us just enough of a drop to make sleeping comfortable on nights when there is no breeze.

We shall see!

ok folks I will try to answer some of the questions as best I can - but please be kind as I'm not an engineer (the engineer in the family sadly passed away last year).

Firstly, just to clarify we don't have village gas so that is not an option for us. Currently the house has 3 open fireplaces and electric radiators which are not up to current standards by a long way (as is the wiring). The house had a fire and is a eco-label G for the purposes of the energy rating. After our renovation it will be an A.

We will be installing a wood gasification boiler - using 50cm buches - not pellets - the cost of pellet boilers is too high for the convenience benefit in our opinion and looks like its 4 x the cost of a wood gasification boiler.

Solarbayer Wood Gasification Boilers

For the Canadien Well:

length of piping is 200m - this will be filled with eau mono éthylène-glycol. That is to heat/cool approx 400m3 air. Fonctionnement hiver - puissance totale échangée: 1,25 kW
Régime eau: 8/6,6°C, débit 750 l/h, DP = 10,5 kPa
T air entrée / sortie: -7°C (HR 90%) / 1,4°C, débit 400 m3/h
Fonctionnement été - puissance totale échangée: 2,3 kW
Régime eau: 12/14,5°C, débit 750 l/h, DP = 9,9 kPa
T air entrée / sortie: 32°C (HR 40%) / 18,3°C, débit 400 m3/h

If you did the digging out yourself you'd save a fair chunk of the installation cost - I'm not very good at driving diggers so I left that to the experts but many self builders do it themselves.

To quote from the thermal study we've had done which includes all the energy efficiency we are putting in here are the proposed future running costs:

Heating 491,49€ per year

Hot water (using solar thermal system) 33,94€ per year

Ventiliaton/circulation of air from double flux/pc 112,65€ per year

Total costs of running the house: 1190€ of which heating, cooling and hot water is predicted to be 511€/an. Obviously it will be a few years before we can validate this. The cost for running the new house should be 3,4 €/m².an.

Our last house also stone in same village was 130m2 with wall and roof insulation, double glazing, air to air PAC/clime, woodburner, electric radiators (only used when really cold in bedrooms in Dec to Feb) and based on 2 adults and 1 child our electricity was around 1800 euro per year and our wood around 400 per year which is approx 17€/m².an

I roughly forecast therefore that the heating, hot water and general energy usage would be in our new house 2 times that of our previous house (we now have 3 girls...that's at least 5 showers a day) so I am reckoning our bill would have increased to around 4000 euro a year if we'd had the same set up. A scary number.

The installation costs for all the energy/heating/insulation/windows on the old house were around 300 euro per m2. The installation costs for the energy/heating/insulation/windows on the new house are around 400 euro per m2. So yes being more eco friendly is more expensive on the initial installation however the ongoing running costs are lower and it is the ongoing costs which we are focusing on with the house intended as a lifetime home. I am intending to take advantage of the credit impots for the work and it's all being done by qualified French registered installers. I am also looking into the eco-pret taux zero (30,000 euro) for a bundle of work to fund the renovation. We could do the renovation cheaper by not investing in this type of technology and most most people would not have gone down our route. We are spending a lot on the project initally (at the expense of finishing the house cosmetically) with the intention that the savings will come from lower running costs in the future and somehow we'll always find the means of finishing off the bedroom floor in the way or another.

I am fully aware there is not a justifiable return on investment for a project like this...its a passion and ROI is not the reason we are doing it. We want a comfortable home, albeit accepting it is big (yes we know it's big and if you want lower bills we could just have a smaller house...) it's a lifestyle choice, its a health choice, its a doing something different and its an ecologically friendly choice. For my husband it's the ability whilst earning at present to invest now and not have to earn as much to live comfortably later...the ecological aspect is an extra positive but it's really the ability to generate low cost hot water, cooling and heating which appeals to him. In the long term he'd like to generate energy too but that's just a step too far for our budget at the moment.

I always said I wanted the house to be a low consumation - batiment basse's how it fares when judged on the current reglementations the newly renovated house will have a performance of:

CepmaxRT2005 37,9 kWh/m²SHON/an - (réglementaireCepmaxRT2005ObjectifzoneH3:80kwh/m²/an)
LABELMINERGIE 25,3 kWh/m²SRE/an (Totalénergieprimaireprojet,baseMINERGIEObjectif:38kWh/m²/an
LABELBBC 25,7 kWh/m²SHON/an (Energieprimaire,baseEFFINERGIEObjectifzoneH3:64kWh/m²/an)
REGLEMENTATIONRT2012 69,8 kWh/m²SHONRT/an Energieprimaire,baseRT2012ObjectifzoneH3:75kWh/m²/an

As you can see from the above we will qualify for all of these for what they are worth...the one that interested me was how far off being passive we would for info to be passive we would have needed to be less than 15kwh/m2/an. We come in at 27.1. I think we would have needed external wall insulation to be passive - a shame on a lovely stone house to cover it up (bad enough covering the inside).

LABELMAISONPASSIVE 27,1 kWh/m²SHAB/an Totalbesoinschauffage,baseMaisonPassive–Objectif:15kWh/m²/an

Anyway I hope this is interesting to you and will keep posting photos and updates as we go through the project.

To Mike Butler: Sorry no detail as I rejected the idea. I do know that you have to have a big enough flow into the well ( a dowser could check that) and that water/water heat exchangers are more efficient than air/air so probably 6kw heat for 1kw electricity.

Very interesting comment by Mike Butler and much better informed than mine! Pretty shocking implications as well. I hope he may eventually end up finding someone to market his design at a modest cost which would make this type of system realistic. One has to remember than nearly all "eco" systems rely heavily on subsidies to make any sort of economic sense so that they are really not any sort of answer to the problem they claim to address. The only exception is probably insulation which has no running cost and fairly cheap to install. However ---

Although I suspect the effect of the 80mm internal insulation will be quite modest if the house is, in the end, really well insulated then the benefits of using such an expensive system to provide the heat are greatly reduced. I think the ratio of running costs in France are more or less Wood = 1, Town gas =2, Tank gas or full rate electricity =4. I suspect the installation cost for a wood burning furnace would be about 25% or less than the ground source heat pump (which will mainly be using full rate electricity as the air distribution system has no storage capacity). Assuming a 3:1 efficiency ration for the heat pump then running costs will be very much the same as using wood and very little more than town gas (if available).

I have used multi foil insulation quite extensively in our house and, so far, done very little about heating as we only spend the summer (May-October) in France at the moment. I will almost certainly end up with a very conventional gas boiler/hot water radiator solution with maybe UF or Thermaskirt fitted on the plinths in the kitchen which gives a good balance of installation against running costs over 10-15 years. Disappointing intellectually but "business is business".

If you have a well, no need to dig a big hole, just pump the water out, through a water/water heat exchanger to your radiators/underfloor heating and inject it back elsewhere so that it heats up again to about 13deg. I was quoted €20k, so not viable as more than 10 year payback. I admire you for your contribution to saving the planet, I do so love technology!

Certainly an impresive scheme. I looked inot "eco" solutions for our own stone house in France and concluded that I wouldn't live long enough to reap the benefit (not sure that my children would either).

EG modern gas boiler cost about €1500. Pellet wood burning boiler and heat sink tank (1500L) cost about €12000. Running cost is about 1/2 that of town gas - you get a lot of gas for €10K.

Greta idea though and intellectually and technically very seductive.