 |
|
|
Home  Books GBEzine News HelpDesk Register GreenBuilding.co.uk
|
|
| Green Building Bible, Fourth Edition |
|
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. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.
Posted By: bardoI was going to use wood wool e.g., Savolit with 5mm clay render to match the effect on the straw /clay rendered walls below.
However this would mean many hours fixing noggins to carry the woodwool. So I'm wondering if plasterboard will work, though I wonder if the less permeable performance will cause any issue.
Posted By: bardoslate onto battens, then Pro-Clima solitex membrane laid directly onto 11mm OSBYou'll need dowslope battens between the slating battens and the Intello/OSB surface, otherwise ea batten will be a dam collecting any water.
Posted By: bardoI would have used a less permeable product in retrospectWhy? the more permeability the better. Or do you mean 'more' permeable? OSB (make sure ir's OSB3) is v adequately breatheable, as is plasterboard or woodwool. The OSB can be the airtight layer, if systematically glued and screwed at all joints (over noggins where nec to support joints) and sealed at the perimeter. Then no need for a fragile expensive sheet memrane for airtightness.
Posted By: fostertomPosted By: bardoslate onto battens, then Pro-Clima solitex membrane laid directly onto 11mm OSBYou'll need dowslope battens between the slating battens and the Intello/OSB surface, otherwise ea batten will be a dam collecting any water.Posted By: bardoI would have used a less permeable product in retrospectWhy? the more permeability the better. Or do you mean 'more' permeable? OSB (make sure ir's OSB3) is v adequately breatheable, as is plasterboard or woodwool. The OSB can be the airtight layer, if systematically glued and screwed at all joints (over noggins where nec to support joints) and sealed at the perimeter. Then no need for a fragile expensive sheet memrane for airtightness.
Your buildup is an excellent 'breathing' construction, provided no vapour resisting layer is introduced. Robust because it can re-dry (after extreme conditions, or at winter-end) both outward and inward. The plasterboard or woodwool needn't have noggings, from any air/vapour-tight point of view; either can be punctured at will e.g. by electricans.
Posted By: djhPosted By: bardoI was going to use wood wool e.g., Savolit with 5mm clay render to match the effect on the straw /clay rendered walls below.
That sounds like a reasonable idea, we have similar but with lime plaster instead of clay plaster.
CheersHowever this would mean many hours fixing noggins to carry the woodwool. So I'm wondering if plasterboard will work, though I wonder if the less permeable performance will cause any issue.
I don't understand why the woodwool will need noggins but the plasterboard won't? I don't think the permeability of plasterboard will affect anything, given a VCL behind it even if the VCL is variable.
Posted By: fostertomYou described the inner membrane as 'an intello or Thermofloc VSD airtight membrane', not as a vapour barrier - check?
They are both airtight and vapour check membranes. My understanding was that the OSB3 doesn't breathe so well which could lead to excess moisture held in the sheepswool insulation. I was also under the impression that plasterboard doesn't breath so well either - hence the development of breathboard as a replacement.
Pity, that. My tinkering with WUFI some time ago showed that a breathing construction able to re-dry both inward and outward, robustly trumped reliance on any inboard expensive fragile 'designed to fail' vapour barrier.
I like the idea of this however I was told by an eco building company that the relatively low permeability of OSB3 could cause issues with moisture retention. I have heard the same from two different 'expert' sources.
As far as wetting of OSB sheathing, if min 40% of the insulation value is placed outboard of the OSB, it never wets, in a breathing construction.
Posted By: fostertomAs far as wetting of OSB sheathing, if min 40% of the insulation value is placed outboard of the OSB, it never wets, in a breathing construction.
Posted By: fostertomYeah I know - that's the trouble with using deep I-joists and is why EWI-like solutions are best (what's to be learned from this case, for anyone else reading and planning).
Posted By: djhbardo wrote: "The ijoists run at 600mm centres. Looking at the woodwool tech sheet it suggests noggins to reduce the span when there's nothing solid behind."
Which data sheet are you looking at?https://www.mikewye.co.uk/wp-content/uploads/2017/05/Savolit-Plus-application-guidance-website" >https://www.mikewye.co.uk/wp-content/uploads/2017/05/Savolit-Plus-application-guidance-websitedoesn't mention noggins and specifically says the ends do not need to be supported if sheets are glued together.
But since the ijoists are at 600 mm centres and the boards are 600 x 1200 mm, there are no unsupported ends anyway are there?
Thanks DJH I see that now. Do you still think that plasterboard is the suitable option?
Plasterboard does need noggins, AFAIK.
Posted By: bardoWhy are deep ijoists a problem in this case?Not saying they're a problem - well tested technique. Not about heat loss. Just that it puts timber in the outermost insulation zone, when some interstitial condensation is bound to occur, even if only intermittent. Come to think, it may be the slight heat loss via the web, that keeps the outer 'flange' warmer, warm enough to not get condensation even if it's happening in the insulation an inch away sideways.
Posted By: fostertomYou described the inner membrane as 'an intello or Thermofloc VSD airtight membrane', not as a vapour barrier - check?
Pity, that. My tinkering with WUFI some time ago showed that a breathing construction able to re-dry both inward and outward, robustly trumped reliance on any inboard expensive fragile 'designed to fail' vapour barrier.
As far as wetting of OSB sheathing, if min 40% of the insulation value is placed outboard of the OSB, it never wets, in a breathing construction.
1 to 14 of 14
