Green Building Bible, Fourth Edition |
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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. |
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Posted By: bardoHello all, I've decided to go with Knauf omni fit glass wool. Though still looking at how to best support the insulation. Just using a membrane or mesh doesn't do it for me and I also see the potential issues with boarding up with OSB as was my original plan. There is a polypropylene product on the market which has holes punched through for ventilation and liquid release. This looks good however the price is way too high. And besides if I used this approach I would also want to cover with a glued or taped breather membrane on top to prevent wind. Has anyone on this forum come up with or heard of an alternative solution? I can see that a strong synthetic mateiral in this situation has merit.
Posted By: djhSorry but it's late and although I've reread the thread I seem to have lost the plot. What was the problem with OSB? And why is plastic now the right answer, especially when its main benefit of water/airtightness is compromised by holes?
We're talking about supporting insulation in a void under the ground floor, yes?
Posted By: GreenPaddyHi Bardo,
cut from an earlier message above...
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What about running a foil faced breathable membrane under the JJI's, running perp to the JJI's?
Start by fixing a timber 25x50 batten to the external block underbuild, at JJI underside height. Staple (and glue) the VPM to that batten, to give a seal to the wall. Then, VPM to first JJI, passing under it, bring the VPM up the vert face of the lower flange and onto the top side of that flange, fold back on itself, staple through the double thickness of VPM onto the top side of the flange, then go back down side of flange, and across to next JJI, passing under it, before repeating.
The foil should face the solum! That will give a well supported continuous layer, at full JJI depth, not losing the depth of the lower flange. You could actually let the foil VPM droop below the JJI's, by say 100mm, and even put 400mm of the cheap loft roll 44 (Uvalue for that arrangement = 0.12W/mK).
That's deff how I'd do it, and not just on paper, have done that on a previous project. Remember to fluff up the wool insulation as you install it, so it's got lots of air en-trained in it, and not squashed, as it comes out of the roll.
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The foil faced vapour permeable membrane should be around £2/m2, but see what your local merchant has. You don't NEED to use foil faced, but it's a bit tougher, and enhances the Uvalue a little. Also, there is the possibility of getting some condensation on the outer surface, when the strange weather occurrence of very cold for several days, then much milder damp weather, so the foil face gives a slightly more water repellent surface.
You could just get the cheapest house wrap VPM, at 50p/m2. I don't use netting, as I feel a continuous layer is better, not least in reducing wind washing, but it's not wrong.
I would lay a vapour check on the top of the JJI's, before fixing the flooring, to improve air tightness, but don't ask the question on here, as you'll get lots of different equally well argued reasons. Make the floor air tight in what ever way you see fit (PU glue on every board edge etc) is a must. You've a breathable house, so continue that through the floor, into the void, and show that on your drawings so the BSO can confirm he's happy with that approach.
Posted By: djhNote that breathable membranes are VAPOUR permeable, but are WATERPROOF. Keeping liquid water out of a building is their purpose in life.
Posted By: WillInAberdeenScaffold debris netting?
Posted By: tonyI would go down there and insulate with inorganic quilt between joists from underneath, assumed 100mm then add 100mm eps under that, More is betterAgreed
Posted By: monkeywoodThere’s a thread about filling the void/max depths and another regarding replacing suspended timbers with concrete - I will go off for a deep dive into those! Thanks all for your time.
Posted By: monkeywoodI’ve done that a few times and there were lots of concrete pouring suggestions (and lots of disappearing off the face of the earth..) It’s proving difficult to get anyone to turn up to even have a look at the moment!
Posted By: monkeywoodHi Tony, in the dining room, at its deepest, about 1.25-1.5m gradually getting shallower towards the front of the house where it is about 0.5m at its shallowest.
Posted By: monkeywoodThanks all for your comments, suggestions and useful links. I think I’ve found someone who can help!