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Author Topic: New project in the Massif Central  (Read 2078 times)
Le Hobbit
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« on: August 24, 2020, 09:23:13 PM »

After a long search we have finally bought a granite house to renovate in a remote part of Correze in Central France. The property is located in the Millevaches Parc Naturel Regional at an altitude of 810 metres above sea level. Climate is semi-montane with normally warm to hot summers and cold, often snowy winters. More recently winters have been milder and wetter and summers hotter and drier.

The house is a complete renovation and comes with 4 hectares of attached land which is mainly native woodland. There is a good supply of wood for heating.

We plan to insulate the house by having a new galvanised and painted standing seam roof (bac acier) with 120mm of PIR bonded to the roof panels and stll on the underside foming a sandwich panel. Under this there will be an attic floor with 150mm of wood fibre/sheepwool or similar insulation between the rafters. This will be boarded over in the attic with OSB or similar, with pine cladding on the ceiling side. The external walls of the stone built house will be rendered on the inside with approximately 80-100mm of hemp-lime and then a lime plaster on top. The ground floor will be pine flooring over an existing concrete slab /block floor with insulation between the chevrons. In the adjoining 30 m2 stable which we will turn into a lounge/snug we will lay a hemp-lime insulating floor slab over 200mm of drainage aggregate with pine flooring over the top. Double/triple glazing throughout. All windows have well fitting wooden shutters for extra bad weather insulation and also for keeping heat out.


The house is built into the hillside so all of the ground floor rear wall (north facing) is below ground level. For this aspect we plan to build an internal wall using ISOHemp blocks 90mm thick and infilling the gap behind with loose hemp lime, tamped down. This is on the advice of the manufacturer. The ground floor is currently one large kitchen/diner which is approximately 50 m2 and the adjoining stable of 30m2. Upstairs is currently one huge space of 90m2 with the framework timber in place to create a spacious attic (storage only)

For heating we have purchased a brand new Burley Wakerley wood burner which is super efficient and will be room sealed. It produces 12kw nominally and up to 18.3kw on max output. Also we have a tusty Jotul F3 which will go in the snug and that is another 6kw. Upstairs we will have electric radiators and heated towel rails for the bathrooms.

I wanted some advice on various products.

For the ground floor there is a concrete block and beam floor over laying the small original cellar. Under the rest of the concrete floor is the bed rock. Currently it is partly tiled but we wish to remove the tiles, laying treated wooden chevrons and fix a pine wooden floor over the top. To insulate between the chevrons we were thinking of 50 to 75mm of either PIR board or similar.

Is there anything more eco we can use than PIR? We want to avoid polystyrene if possible. Could we use hemp or hemp lime over the concrete and between the floor chevrons?? As the house is built into the hillside there is currently some damp intrusion on the rear wall, however the old slate roof has no guttering and all rainwater is concentrated at the back of the house with nowhere to go. Also the external pointing has been done in cement and there are some cement rendered parts too. Once we have repointed with lime and have guttering/drainage our builder thinks the wall will dry out nicely.

For the attic floor insulation between the framework we were thinking of 150mm of sheep's wool? We would like a natural slate roof or even a larch shingle roof, but the prices are prohibitive on a 155m2 roof. We like Bac Acier and think it is smart and contemporary. With 120mm of Bonded PIR insulation it should perform well. We will also have three sun tunnels on the rear roof elevation to bring extra light in , though the attic and to the 1st and 2nd floors.

What are your thoughts on our project? Any suggestions?
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kdmnx
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« Reply #1 on: August 25, 2020, 06:50:38 AM »

Welcome! You’ve come to the right place. Every 2nd member on here seems to be renovating a house in France at the moment!

Just an edit to come back and and answer your question:

Generally PIR is the best product. Its insulation qualities are just too good in comparison to anything else. PIR is also very easy to handle and install, and it lasts for many decades. So-called "natural" products (eg hemp or sheeps-wool) are poor in comparison. You need many times the thickness for the same insulation level, they attract mould and vermin, they deteriorate unless conditions are perfect.

I'm with you, single-use plastics, and packaging in particular (which is designed to be disposed of), is disgusting. However if you do a good job on the renovation then the PIR will still be there in 50 years or more doing its job. If you are concerned about indoor air quality, then focus on ensuring adequate ventilation. 
« Last Edit: August 25, 2020, 12:58:01 PM by kdmnx » Logged

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todthedog
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« Reply #2 on: August 25, 2020, 12:21:43 PM »

Sounds a great project.
Any pics, we love pics my precious!
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Kidwelly South Wales
mr smith
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« Reply #3 on: August 25, 2020, 08:02:05 PM »

As the house is built into the hillside there is currently some damp intrusion on the rear wall, however the old slate roof has no guttering and all rainwater is concentrated at the back of the house with nowhere to go. Also the external pointing has been done in cement and there are some cement rendered parts too. Once we have repointed with lime and have guttering/drainage our builder thinks the wall will dry out nicely.


After 10 years with guttering there is still damp in our sunken wall, I would accept it will always be there and cover with a ventilated stud wall. The other option is to leave exposed stonework as we have in another section and this works OK.
The only major issue to the exposed wall was an electrical fault in a plug socket as moisture condensed in the unit.

If you live there full time the house should naturally vent, we have a bit of a humidity issue but we do leave the house locked up for long periods.

Where are you located? We are just outside Auzances.
« Last Edit: August 25, 2020, 08:07:19 PM by mr smith » Logged
AndrewE
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« Reply #4 on: August 25, 2020, 09:44:50 PM »

Welcome! You’ve come to the right place. Every 2nd member on here seems to be renovating a house in France at the moment!
As far as I am concerned, just keeping a (i.e. just one) well-built Victorian semi in good condition, with on-going upgrades/sympathetic modernisation, is all I can cope with!
I've almost completed replacing the original sash windows with identical but double-glazed plastic ones, but I do recognise that the potential problem from condensation on walls instead of windows - it probably needs a MVHR system as a consequence.  We still need to alter the rainwater drainage, replace the gutters (and have it repointed,) rebuild the kitchen etc., but it is a lovely house to live in.
We bought it for the garden (and for its location,) the house just came with it!
A
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todthedog
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« Reply #5 on: August 26, 2020, 06:23:05 AM »

We had a continuously running single room heat exchanger in the kitchen living room 50m2. Consumed diddly squat electricity but kept damp at bay.
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Kidwelly South Wales
Barrie
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« Reply #6 on: August 26, 2020, 11:55:56 AM »

Ditto with two 30m2 changing rooms at a water sports club.

Regular showers each weekend introduced humidity and condensation which was then locked in for a week and re-painting was required each year. Now with the continuously running fans having been installed two years ago the paintwork still looks as good as new.

Not that the showers have been used recently  fume
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Le Hobbit
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« Reply #7 on: September 27, 2020, 05:36:14 PM »



[/quote]

After 10 years with guttering there is still damp in our sunken wall, I would accept it will always be there and cover with a ventilated stud wall. The other option is to leave exposed stonework as we have in another section and this works OK.
The only major issue to the exposed wall was an electrical fault in a plug socket as moisture condensed in the unit.

If you live there full time the house should naturally vent, we have a bit of a humidity issue but we do leave the house locked up for long periods.

Where are you located? We are just outside Auzances.

[/quote]

Hi there, Mr Smith. We have bought our place in the Haute Correze about ten minutes south of Bugeat high on the Plateau Millevaches. We have friends near Auzances in the commune of Charron . Interesting to hear your comments. Are you speaking about your property near Auzances? We did think about a stud wall but want to avoid anything like plasterboard. We are very keen on using hemp lime as much possible. I bought the excellent book "The Hempcrete Book" by William Stanwix and Alex Sparrow and there is loads of great info in it. The French company that supply IsoHemp blocks have said we should not leave an air gap but infill the gap between the hemp block wall and original stone wall with loose fill hemp lime (tamped down) so that there is no void. I am worried about damp incursion. I have read that hemp lime should not be deployed in below ground situations, but it is only the rear wall which is below ground? Apparently hmp lime will take some element of damp? We plan to excavate behind the house to the depth of about a metre and to lay a plastic honeycomb membrane against the rear wall. This sits proud of the wall so allows air flow. We then backfill with grade gravel and drainage tubes. What do you reckon?
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mr smith
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« Reply #8 on: October 07, 2020, 12:34:30 PM »

Hi There,

Ahh you are probably about an hour from us. I know Charron not far from us.

Our house near Auzances has the the whole of one side under ground up to the first floor. I would personally either leave exposed and let it naturally vent or fit a wall with a gap. We have a lime rendered section and it just blows render off and stains etc.

Why do you not want to use plasterboard? I would be right to be worried about backfilling as any permeable product will bring stains/moisture through. We get all sorts of stains/mould show on the lime pointing on the exposed wall but I just think this adds caricature and we just avoid putting pictures, coat hooks etc on it.

A french drain along the back will help reduce but don't go overboard as rising damp will still be present. Also you could actually cause a bigger problem as the rear may not have been pointed and be very loose drystone allowing your newly made drain or surface run off pushing deep into the walls! I have a section in the barn that springs a little leak in heavy rain due to water build up from behind. You are yet do witness the heavy thunderstorms we get in the area!

You are welcome to have a look at ours if you are ever visiting your friends in Charron, having said that travel restrictions do not seem to be going anywhere so may not make it down for a while :-(

 
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