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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorCerisy
    • CommentTimeOct 8th 2014
     
    So we tried to buy a little house round the corner, but stopped when the "dutch" auction began to get silly. But, it stirred us into thinking what else is for sale that would be suitable for our son and his family to take on - with our help of course!! (and, yes, we still have the new house to finish, but this to give us something to do afterwards!!)

    So there's this old house up for sale on the other side of the village - asking price 15,000 euros. It is a stone and mud built two storey building that was used as a dwelling before the war with a barn alongside. The first floors have been removed and the farmer has kept hay in there. The "house" side is around 6m wide x 11m long, with the barn side a bit longer. The old walls are a bit rough, but apart from one corner, in pretty good shape. The roof is okay.

    I was thinking that we could follow the same theme as our new house - basically build a timber house within the old stone walls. We could put together frames clad in OSB (the OSB would help keep the vermin out!!), floor structure on top, then same again for the first floor walls, etc. Insulate the frames, then more insulation internally and another insulated internal wall to carry the services and plasterboard. Overall around 325mm insulation + the very thick stone walls. So no more cladding, but a structure that doesn't impinge on the existing walls and a chance of making it air-tight.

    Anyone else gone down that sort of route or can see any serious problems???
    • CommentAuthorringi
    • CommentTimeOct 8th 2014
     
    You loose LOTS of space.

    Where in the makeup will you fit the windows, and how will they be fixed?
    • CommentAuthorCerisy
    • CommentTimeOct 8th 2014
     
    Ringi - looking to fix the windows / doors to the timber frame and have an insulated "tunnel" to the stone walls. It will be quite a deep reveal on the outside, but they need to be in the insulated space.

    Yes, we'll loose about 80cms off the width of 5.8m (the length is less of an problem), but there are a number of issues to be resolved ... the stone walls aren't that good on the internal face and will take loads of work to get them to any sort of acceptable condition to be exposed, our expertise is timber framing (that's what our house and garage are built of!) and we want to provide a high level of insulation. I appreciate these thick stone walls are excellent at regulating temp differences, but in our current house (around 300 years old) when it gets cold it does take quite a bit of heating to keep it warm. Plus a timber structure internally will make fitting in the first floor much easier and we should be able to make it airtight. At least that the current thinking - just got to get some local advice on how we can fit the septic tank in before we work out an offer - maybe!!
  1.  
    I can see the attractions of putting a timber frame inside the stone/mud walls - but the place has been unheated for 100+ years (?). Do you (or anyone else reading this) anticipate any problems when the inside surface is enclosed and the airflow stopped to one side of the walls.
    • CommentAuthorringi
    • CommentTimeOct 8th 2014
     
    Why stop the airflow to one side of the wall? If I was doing this I would just put small vents in the stone wall.

    Just thinking of the top of my head, maybe even fit single glazing in the stone wall, and double glazing in the inner timber frame, so the insulation detailing does not need to cope with rain.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 9th 2014
     
    Forgotten where you live, but is condensation, or severe weather a problem where you are a problem?
    Just thinking aloud, and don't know anyone who has done it, but could you spray the inside of the walls with a couple of inches of PU foam and then build your timber frame inside.
    Also have you done U-Value calculations on different wall make ups to see where the optimal value is when you take ACH into account.
    • CommentAuthorringi
    • CommentTimeOct 9th 2014
     
    What is ACH?
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 9th 2014
     
    Air Changes per Hour
    • CommentAuthorEd Davies
    • CommentTimeOct 9th 2014 edited
     
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 9th 2014
     
    Thanks Ed
    Similar climate to me then.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2014
     
    Normandy - wet windy UK climate but more sun.

    New house within old walls is top ideal solution. Old walls are happy forever, given a good roof over, when effectively freestanding. Key is that they 'see' outdoor climate equally on both faces. So
    Posted By: ringismall vents in the stone wall
    isn't enough - very big vents top and bottom are needed to do the trick.

    http://www.buildingscience.com/documents/reports/rr-0907-ventilated-wall-claddings-review-performance-modeling
    advises such ventilation; Fraunhofer (google for it) goes even further, advising the big ventilation mentioned above.
    • CommentAuthorCerisy
    • CommentTimeOct 9th 2014
     
    Thanks for the reassurance - saw it again this morning and it's growing on me, especially the amazing views to the south and north (although that does mean it's pretty windy!!).

    Interesting to think on how to fit vents to ventilate the inside face of the old stone walls, especially as I was pointing out the issues of holes in the walls and vermin ingress when we saw a mouse run into the wall - couldn't have asked for a better example!!

    Fortunately my son and his missus want to have an upside down house to enjoy the views, so I can use the bedroom, etc, walls to support the floor joists - simples!!

    Spot on Ed - Cerisy la Salle - can't hide behind that name anymore!! Definitely seasonal like the UK, but a few degrees warmer and loads more space!! This old building comes with over half an acre.
  2.  
    For 15000 go for it!

    Building looks solid, straight lines. Even the corner thats blown out looks like a problem with water from the roof falling on the earth wall rather than structural.

    Im surprised it doesn't have larger overhangs considering the climate.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2014
     
    Climate doesn't seem to generate vernacular overhangs - Dartmoor/cob has close eaves and verges. Overhangs IMO were done mainly for visual effect, even way back.
    • CommentAuthornigelm
    • CommentTimeOct 9th 2014
     
    We have a similar project in development at the moment, although the barn is further south in the Dordogne.

    The construction is similar with thick stone walls, we are planning to use mineral wool as internal insulation with a new false wall using light steel studs. This is partly a cost decision, these are the materials available local at an affordable cost. The steel stud will be braced against to the stone and faced with Fermacell. I have a WUFI analysis of this construction and the results are very favorable with no real buildup of moisture in the stone walls.

    The roof will be externally insulated with rigid foam so that we can keep the timber structure exposed. We have adopted a French conservation method with the roof covering, the tiles are removed and the roof covered with galvanized steel sheet, the tiles then re-attached with spray foam. the tiles then act as a decorative layer only.

    Based upon the WUFI data we are having to replace the ends of the roof king post roof trusses with steel hangars as there is a risk of rot there.

    The floor with have either perimeter insulation or more conventional foam insulation under a concrete slab, it depends on how deep we can dig without undermining the walls.

    We are also going to create a thermal break where the internal stone walls meet the outer walls, this is not fully resolved yet as a detail.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2014
     
    Posted By: nigelmThe roof will be externally insulated with rigid foam so that we can keep the timber structure exposed. We have adopted a French conservation method with the roof covering, the tiles are removed and the roof covered with galvanized steel sheet, the tiles then re-attached with spray foam. the tiles then act as a decorative layer only.
    If you're putting insulation under the steel, that's a certain disaster, unless lots of outside-air ventilation between insulation top and steel underside.
    Can't believe that's a 'conservation method' - sounds like horrific ignorant local-builder bodge.
    • CommentAuthornigelm
    • CommentTimeOct 9th 2014
     
    Apologies Tom, my poor explanation.

    The normal process is to remove the tiles, add the steel sheet than replace the tiles, this makes the roof weather tight but allows the undulations that develop over the years to be left intact. A lot of roofs have a low pitch, add in some roof sag and canal tiles, the roof leaks.
    We have just added some insulation under the steel sheet. You can get fiber cement sheet with insulation pre-bonded for the same job, but this is rigid and needs the roof leveling out before its fitted. (a dead level roof looks odd on a old building).
    • CommentAuthorringi
    • CommentTimeOct 9th 2014
     
    Does the spacing on the steel sheet “channels” match the canal tiles?

    Personally I would like a 50mm gap well ventilated under the steel sheet, and permeable membrane over the insulation. As you will get a leak one day, or condensation….

    I also question steel sheet due to rust, as you may get pockets of water sitting under some of the tiles.
    • CommentAuthorEd Davies
    • CommentTimeOct 9th 2014 edited
     
    Posted By: nigelmWe have just added some insulation under the steel sheet.
    What stops condensation under the steel sheet? Is the insulation bonded to the steel to make it airtight?
    • CommentAuthorCerisy
    • CommentTimeOct 9th 2014
     
    Up t'north the roofs are at 45 degrees, presumably to shift the snow off when it, occasionally, arrives from the East. There is a distinct dip in the roof over the part we will renovate first - probably where the old chimney and dividing wall were taken out. We will have to get advice on that once we can access the roof space. Strangely the owner got some reparation floor joists and floor boards after the war, but used them to make a floor to the roof space around 5m off the current floor level! I suspect he was never going to make it habitable again and wanted the head room to store his hay bales.

    One side of this attic floor has a huge sag on it as it is supported off a too small timber beam - trouble is how do we get up 5m to either strip it out or prop it up and fit a new beam. Perhaps either get a friendly farmer with his telescopic lifter or wait until we build the first floor and have a working surface a bit closer!!

    Good search Bot de paille, shame the photos don't show the small, water filled, quarry to the east!! Different!
  3.  
    I would think carefully about a timber cavity inside if there is a chance of a vermin problem. There is nothing worse than not being able to sleep at night with small furrys making a racket running around the cavity between the walls. OSB will do nothing to stop them they will be through that in a night. I would do everything to avoid a cavity.
  4.  
    Ive seen someone do a similar renovation in a stone barn using Siporex blocs, seemed to work out well,
    though I haven't seen it since it was built to know if it developed any problems later.
    • CommentAuthornigelm
    • CommentTimeOct 9th 2014
     
    The steel is galvanized and plasti-coated to color match the tiles (roughly), guaranteed for 30 years.

    We have fitted battens and membrane under the steel because of the condensation, there is a fleece backed option that will wick the moisture away.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2014
     
    Maybe different climate down south but all northern experience (and WUFI) says insulation under half hearted ventilation under steel is a disaster - look at any decaying caravan. Fleece merely postpones the condensation dripping on cows under an uninsulated agric roof.
    • CommentAuthornigelm
    • CommentTimeOct 9th 2014
     
    The climate is very different, I have only run the wall construction through WUFI using local UK data and Dordogne data and the results are very different.

    In terms of the roof the condensation I was assuming the roofing membrane underneath would stop any moisture penetrating the roof structure or am I missing something.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2014
     
    No it won't - pinholes and hairlines will let water vapour in, then prevent it drying out again. Exactly like a soggy caravan! As the vapour condenses to liquid on the steel underside, it leaves a 'vacuum' of vapour which sucks yet more in thro the cracks. It's a one-way pump, with liquid water content accumulating year by year.
  5.  
    You don't like caravans do you Tom? That must be the 10th time you have been denegraded them in 6 months? Me too:wink:
    •  
      CommentAuthorfostertom
    • CommentTimeOct 10th 2014 edited
     
    No I love caravans - we have 5 oldish ones around the place, for workshop participants' sleeping accommodation, of which one is mobile and is regularly seen in Cornwall etc.

    Knowing these so well, and enlightened by my WUFI studies, I know exactly why they're custom designed to start rotting from day 1 - and it's not leakage, as everyone assumes (well it may be that as well) and dehumidifiers are a waste of time. Only keeping them under cover will save them from exposure to clear night skies, which turn their impermeable roofs into super cooled condensing plates.

    I've seen insulation-removed caravan roofs literally dripping all over with condensation. Just like nigelm's roof, those litres of water have nowhere to go - can't dry inward because of the vinyl wallpaper. So almost immediately, caravans' insulation. roof esp but walls too, is permanently saturated, and so is the timber framing embedded in it. Then its a short race between the rot organisms, and the timber's preservative treatment.

    Nothing to do with leakage - the custom-designed interstitial condensation with inability to dry inwards, does the job on its own.

    Keeping it under cover is the key - a simple rainscreen to roof and walls, with copious thro-ventilation between that and the existing impervious roof, will protect the latter from the super cooling clear night sky. Better still, if insulation is added on top of the existing roof. Or in a new 'van, leave the insulation bare (under a breather membrane) to the ventilated void under the rainscreen.

    That's what I hope to do to our caravans - maybe even the mobile one.

    Having thus discovered the secret of eternal life for any old caravan, have someone pay you to take theirs away, strip all its cheap tat out, nicely wallpaper and furnish it from the auction rooms - and you have a spare bedroom. studio etc for free - instead of the Ă‚ÂŁk's people spend on a habitable 'garden shed'.
    • CommentAuthornigelm
    • CommentTimeOct 10th 2014
     
    Tom, is there a way of utilizing the steel whilst mitigating the condensation roof, a bigger ventilation gap perhaps?

    On the caravan theme there is a small aeroclub at the bottom of our garden. Some of the pilots have parked caravans there for overnight stays and they have erected timber facades and roofs around the caravans. its actually a surprisingly effective camouflage and its not to you are up close you realize they are not in fact timber cabins.
    • CommentAuthorEd Davies
    • CommentTimeOct 10th 2014
     
    How much will the tiles on top of the steel help? I imagine quite a bit in providing insulation and a bit of thermal mass so it takes longer for the rainscreen layer to cool down at night.
   
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