Yvonne Posted July 16, 2005 Share Posted July 16, 2005 We currently have bedrooms in the roof space with a small loft above them. We want to open the whole space up and lose the loft. At the moment the bedrooms are clad with tongue and groove which does not appear to be well insulated behind as when the north wind blows....it howls through these rooms!!Please can anyone advise us on the best products available in France (for DIY'ers) for wind / waterproofing the roof prior to putting in the rock wool , plasterboard etc? Many Thanks,Abi. Link to comment Share on other sites More sharing options...
Gyn_Paul Posted July 17, 2005 Share Posted July 17, 2005 Rather depends on your budget: the multi-layer alu foil/dacron batting is about a cm or 2 thick and dead easy to fit (drape it under the chevrons and staple in place) is apparently the bee's knees (or the D***'s B***'s even) in terms of how good an insulating medium it is. However, it's v. expensive.About the same insulation value would be 200mm rock wool, for which you would have to buy/make framing to hold it in place.It comes in rolls about 200cm long and 120cm wide (I think), has Kraft paper on one face and is relatively easy to lay on a horizontal surface (like the floor of a loft, say), but absolutely vile to manipulate above head height (I know whereof I speak!), but it can be done.Another option would be polystyrene-backed plasterboard, but these are hard to mount and make wind-tight, ~I believe ~ if the chevrons are all higgledy-piggledy.If you can afford it, I'd go for the foil option, because you can nail the t&g lambris back in place afterwards.p Link to comment Share on other sites More sharing options...
Yvonne Posted July 17, 2005 Author Share Posted July 17, 2005 Paul,Thanks for the information. If we go fo the alu foil / dacron stuff, is that all we need behind the plasterboard? will it be water tight and windproof? We don't want to put the lambri back as we hope to plasterboard between the roof supports, leaving the wood exposed.If we go for rockwool, do you know if we have to use a waterproof membrane on the outside?May be a stupid question but what exactly do you mean by 'chevrons'?? Thanks, Abi Link to comment Share on other sites More sharing options...
Wynnstay Posted July 17, 2005 Share Posted July 17, 2005 Just a word of warning. We have two bedrooms with ceilings and another one open to the beams. This large bedroom is well insulated with plasterboard including the spaces between the beams. It has a very large window yet in hot weather it is absolutely unbearably hot - even if the windows are open or the curtains drawn. We always move out of it in hot weather as even an air cooler is insufficient. The other two rooms with ceilings are cool. This is a granite house.We know many people have such rooms which do not suffer the problem but we do.... Best of luckWynnstay Link to comment Share on other sites More sharing options...
Yvonne Posted July 17, 2005 Author Share Posted July 17, 2005 Hmmm..Thanks for the warning. Our house is made from some sort of volcanic rock and is then rendered....No idea what that may do to the conductivity of heat?!Abi Link to comment Share on other sites More sharing options...
Gyn_Paul Posted July 18, 2005 Share Posted July 18, 2005 [quote]Paul, Thanks for the information. If we go fo the alu foil / dacron stuff, is that all we need behind the plasterboard? will it be water tight and windproof? We don't want to put the lambri back as w...[/quote]More of an issue, I suspect, is not so much the finish of the building, but the colour of the roof! Black slates are AS HOT AS HELL ! I was doing some electrical work in my big barn with its slate roof and realised as I climbed the ladder (2 -1/2 storeys) up the inside that it was bloody hot, but didn't grasp until I got the thermometer out and did some measurements that it was 22o on the ground, 35o at the top of the big doors (sort of 1st floor level), 45o at the top, and right high up under the ridge it was 54oC ! next door in the house which has red tiles, it was hot but nowhere near those sort of figures.With that degree of solar gain, it's hardly a surprise that even well insulated roofs get hot. Chevrons are the pieces of wood which run downwards from the top of the roof (the ridge) to the top of the walls (think of the Citroen logo). On a small roof they may be unsupported, on a bigger one they are usually supported by a heavy-duty timber running horizontally from end to end (a purlin or Panne in Fr). The lathes are nailed to the chevrons and slates in turn are nailed or hooked to the lathes. In the case of machine tiles these are manufactured with lugs which hook over the lathes. Sometimes the roof is boarder before adding the lathes.In the case of the old semi-circular canal tuiles the roof is boarded completely and the tiles, in two layer - one up and one down - just sit on boards. These roofs are incredibly heavy, and I suspect their greater thermal mass (allied with the amount of soil which blows into the gaps between the tiles over the years) keeps them a bit cooler.Meanwhile back at the original question; Which of the roof timbers do you want to expose? It would certainly be difficult to fill just the spaces between the chevrons (just remembered what they are in English: rafters!) with the foil and expect to make it wind-tight. In a perfect world you'd take the tiles or slates off, also the lathes, then staple the foil onto the top surface of the rafters (making 'valleys' between them to allow for ventilation), then replace the lathes and the tiles. Big job, though.The continuous rolls of foil can be taped together to make them wind-proof: which in turn will stop rain or snow (hard to think we might ever have snow again) being blown in under tiles, but won't make it waterproof per se. Fix the roof first.you need a damp proof membrane on a house roof where there is a possibility of warm, humid air meeting a cold surface whereon the water vapour will condense out. The problem then is, what do you do with the condensate? I've never used a dpm on a roof I've insulated because I reason that if there is sufficient insulation behind the facing material (be it wooden lambris, plaster board or plastic lambris) then - although there will obviously be a temperature gradient between the cold outside and the warm inside, the facing material will remain sufficiently warm to remain above the dew point. I also like the idea of the structure being able to breathe a bit!Others may have a different view on this however.p Link to comment Share on other sites More sharing options...
Wynnstay Posted July 18, 2005 Share Posted July 18, 2005 Thanks Gyn Paul for that - our roof is slate - probably once black but now gray - and tho we doubt the temp is quite that high for us its not far off! I think I have just joined into a subject that is going to be more use to me personally than I thought when i posted that first warning. Having told you about our current house, we are also just about to buy a tiny cottage in which we hope to use the attic space as another bedroom but were wondering how to make sure our present problem does not occur there too.I can see that the rear roof is red tile and the front slate - I will guess the Maire will want us to make the new roof dark along with the rest of the village. What other knowledge of all this does anyone have? What options have we?What precautions would anyone suggest?::ThanksWynnstay Link to comment Share on other sites More sharing options...
Anton Redman Posted July 18, 2005 Share Posted July 18, 2005 Isulate the ceiling not the roof. Lleave enough soffit ventilation grills to ensure you can get a cross draft through the roof void. Link to comment Share on other sites More sharing options...
Gyn_Paul Posted July 18, 2005 Share Posted July 18, 2005 Well, yes, Anton. But I think the size of the room he's talking about precludes a idea of a separate ceiling.paul Link to comment Share on other sites More sharing options...
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