LaChab

@jayc89 Thanks for the reference to Airguard. I'll have a look. I'm sure Intello is good, but as I've got a cold roof I'm not sure that I need variable membrane, just airtight. Hoping for advice!

Hi, I'd really welcome some thoughts and advice about selecting an air tight membrane for the upper floor ceiling. I've done loads of searches and read lots of topics, but I can't really find an answer. It's an ICF house, with a ventilated cold roof built with attic trusses. My plan is to have some PIR hung under the attic floor joists to give a continuous layer, then possibly some more PIR and/or rockwool in between the joists. But I've no idea what to use for the membrane. I'm sure it needs to be airtight, but would just polythene sheet be good, or do I need something more technical? And do I put it between the plasterboard ceiling and the PIR, or above the PIR and under the truss joists? Or fit both? And any recomendations for what adhesive to use for bonding the membrane to the EPS walls would be great. Thanks for reading,

@craig Thanks for the support for side fix. I went for the original supplier because they're "Internorm Platinum", and I thought they would make the best job of installation. so I was really suprised when I enquired about the fitting spec and found that they just used 330 foam with no membrane / tape at all. As I've said, I think face fix is difficult to conceal behing the plasterboard, especially with a 10mm gap. Hopefully the "new" supplier will work out ok with "i3" sealing.

@craig Thanks for the input. No check reveal, just 15mm stop beads on the Jackon closure. It was mainly the fact that they were unable to guarantee the work if they fitted a "side attached" membrane, despite charging £1k.I've now asked for a quote from another Internorm dealer who actually offer a membrane as an option, although it's still £1k!.

@Russell griffiths Yes, those pictures make the problem a bit obvious! Did you cut into the foam for your cills? We're using thin coat render, so wouldn't be a huge overlap without going into the foam, but still be a big improvement.

@Chanmenie @Russell griffiths Yes, cills first sounds much better. Trouble I hink that would mean having a second lot of scaffold just to do the sides of the reveals. I was intendiung to use the liquid membrane you like before the cill is fitted, so perhaps that and something suitable (silicone? tape?) between the upright side of the cill and the side of the reveal might be ok. Wouldn't be ideal, but probaly waterproof........ The reveals havn't been rendered yet (weather!), so if I found the section of the cills I could "block of" just the lower bit of side render, then patch it in by ladder after the cills have been fitted.

@Mike You're right, it does look a bit of a potential problem.Leaving the render until after the windows are fitted would be a real pain though. I checked with Internorm, and they were ok with doing the render first, so I didn't think much more about it! I'll bring it up with the surveyor when they come to measure up.

@Mike I must confess I haven't considered the cills as much as I perhaps should have! It's been a bit of a journey deciding on the window design. The Internorm salesman showed us some aluminium cills that looked quite good. They attach to the "extra lump" that appears underneath the window. They've got upstands at each end, which makes them quite robust. Much better than the rather flimsy ones we've got now. I've only arranged for the sides and top of the reveal to be rendered to stop beads. The bottom is just being finished with a stop bead on the vertical surface. Then I was going to paint the bottom reveal with liquid membrane, as I've seen on here, and possibly even add a strip of actual membrane. The windows are going to be 120mm inset, so about 150mm cills. Hope that makes sense!

@Chanmenie Thanks

@Chanmenie Thanks for the info. As the windows I want have got such a narrow internal face it would certainly seem easier to use liquid membrane on the inside "join". And we could do it ourselves after the fitters have left. What liquid membrane did you use?

@ToughButterCup We've a bit of a way to go for wardrobes! I look forward to it.

@JamesP I very much share your sentiments. We're doing a lot less DiY this time and find contractors generally very frustrating. They always seem in too much of a hurry to bother with the finer details. Anyway, lots of DiY after the windows are ffitted! Very frustrating that Internorm make such excellent windows but seem less good for fitting.

@ToughButterCup @JamesPI think you've misunderstood. I posted my query as I had doubts about the effectiveness of using only foam to install the windows, when my existing ones have got factory fitted airtight tape. I also couldn't see how "face fitted" tapes were feasible. Actually what I'm most concerned about is the installer being unable to guarantee the work if I specify factory fitted tapes. It gives me no confidence in their abilities at all. I do also think that charging an extra £1000 to fit the windows if I want "pre fitted" tapes is a bit excessive. I'd assumed that that was standard!

@FarmerN Thanks for the observations. I had considered plastering the reveals, but now I've got to have at least 8mm gap around the window I'll stick with pb. Much easier to cover any tape.

@G and J I hadn't looked at that sort of tape. Looks an interesting alternative to gun foam. No, ICF with high density EPS reveals. @Gone West That's very reassuring. I'd be delighted with a reading anything like that. It seems that foam and adhesive tape is the way to go.

@Mike Thanks for the advice. I feel a bit reassured!

@Mike As it's into dense EPS I think they use screws. Good thought to ask specifically about underneath. I'm having the outside of the reveals rendered with 15mm stop beads before the windows are fitted, so would prefer to aim for a 7.5 / 8mm gap as you're suggesting. I do still think it's a bit poor that they can't use factory fitted tape though. @Mattg4321 I came across that when I looked up the Tescon profil stuff. Looks almost as good as factory fitted for pvcu windows. Trouble is I think they'll charge me £1050 for fitting it! Were you able to use it as you fitted your own windows?

@Mike The installer's almost insisting on 10mm, which seems ott to me. we've used an extension tube on the gun before, whic h would get it into 6mm easily. If I aimed for a minimum of 8mm, that sounds doable. But what about the bottom? presumably the foam gets completely squashed out there? You're right, it's ICF (Jackon). So no VCL. The reveal is really simple as there's just a 350mm closure covering both EPS and the core. Made from high density (120?) EPS and 45mm thick. Makes the windows very easy to install. I thought! Perhaps I just need to have more faith in FM330.

@Redbeard They are. And the limited width of the internal frame is why I don't think taping to it is the way to go. And worsened by the installer virtually insisting on a 10mm gap around the frame. I'm probably just being obsessive, but relying on foam for an airtight seal just doesn't seem right. I'll ask more detailed questions about fitting of some other Internorm dealers.

@Redbeard Just noticed that in the left hand picture it shows the Alu cladding.

@Redbeard You had me worried there! And I've seen them! Like you, I can't see it specified, but this description talks about the "hidden sash" from the outside.

@Redbeard Thanks for looking! I'm quite likely misinterpreting the diagram, but as far as I can see there's only about 15mm of frame on the inside, before the opening bit (25mm less about 10mm) And they're such nice looking windows!

@MikeSharp01 Exactly what they're saying to us! I can't really see how it can be damaged. Bet it's fitted ok in Austria! With a guarantee!

@Redbeard Sorry if I'm misunderstanding, but with a 10mm gap and 15mm of PB, there would only be <5mm for the tape. The factory fitted tape seems much the best, but what a ridiculous price!

@Redbeard I was intending to just line the reveal with plasterboard, so with a 10mm gap round the windows AFIC see that doesn't really give room to stick tape. Also we're intending to use KF520s, which have got a rather tight tolerance inside.