Airtight tape on 3g windows. Or not?

[LaChab]

Hi,

 

I'd really welcome peoples views on the  need for airtight tape when having windows fitted.

 

I'm going through an Internorm quote for a new build, and I've been told that installation is with Illbruck FM330, but no airtight tape.

 

I queried this and was told that for £600 extra they would fit ProClima Tescon Profil.

I queried this as well, as it doesn't look like the correct tape to me, as it will show on the inside of the window.

So latest, I can pay an extra £1050 and have factory fitted tape, just like on my existing 15 year old windows.

But despite the cost, they won't guarantee it, as apparently it's easy to damage.

 

It seems a bit mad to me to fit 0.7 glazing with only foam, but is that normal now?

All help much appreciated.

[JohnMo]

4 minutes ago, LaChab said:

seems a bit mad to me to fit 0.7 glazing

The glazing is normally the worst performing aspect a good quality windows. You are after two things airtightness and no thermal bridges. So is insulation spray foam better or equal performance (U value) compared to the window frame - yes/no.

Is the spray foam airtight if installed correctly - yes/no

[LaChab]

@JohnMo Thermal conductivity for the 330 is 36 mW/m.K. No idea how that compares!

Illbruck say it's airtight (< 0.1 m³/(h.m) at 1750 Pa), but presumably it relies upon perfect installation. 

I've spect ages browsing "windows" on here, and I'd got the impression that an airtightness tape was very popular. There's certainly a good selection for sale.

[Post and beam]

Why wouldn't you install the tape yourself?

[Russell griffiths]

Look on the illbruck site for their window fitting packages 

you can use illbruck fm330 and then a very fluid paste that comes from a sausage gun, you spread this over the foam like a silicon sealant, but smooth it out with a paintbrush. 
 

I was so impressed with it I bought an extra 24 sausages and used it for loads of extra places. 
 

if you can do this bit yourself there’s a £500 saving. 

[Redbeard]

I have seen very poor taping done by contractors and very good taping done by householders. There will also be lots of crossover, of course. Not sure why the Profil would necessarily show on the inside. What shows (or doesn't) depends on the depth of the reveal finish. Pro Clima Profil is designed with a split backing-tape specifically for windows. Equally there is no reason for the split tape if you are good at applying tape, so you can use Tescon Vana or similar from the same manuf'r.

[LaChab]

@Post and beam  I'd like to! But the tape needs attaching to the sides of the windows before they're fitted. Which is what the £1050 is for apparently. So we'd have to fit the windows ourselves, and they're very heavy!

 

@Russell griffiths That sounds interesting. I'll have a browse. Did you fit your own windows?

[LaChab]

@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.

[Redbeard]

Most window-taping I have done has been onto the inner face of the window (by less than the depth of the plaster or plasterboard) and thence onto the masonry. It was done after the windows were fitted.

[MikeSharp01]

2 minutes ago, LaChab said:

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.

We designed ours to have the ProClima Tescon Profil tape on the frame face 10mm and then hidden by 12.5mm Plaster board, to be fair we also asked the window company to fit the tape on the outer of the frame but they said they would not do it because it would get damaged in the fit. 

[LaChab]

@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!

[LaChab]

@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]

5 minutes ago, LaChab said:

@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!

 

I guess it depends how much of the stile you can 'lose'. Usually you can 'lose' up to 20mm without the end result looking stupid. If I had the set-up you have I'd maybe use 2 x 9.5mm plasterboard and once 3mm skim was on you'd have more room for tape. 

Edited 15 hours ago by Redbeard

[Redbeard]

11 minutes ago, LaChab said:

Also we're intending to use KF520s, which have got a rather tight tolerance inside.

 

Just searched for what KF520s are! Looks enough space there for what I have described but I may be wrong, or you may just like to see a lot more frame than I'm happy with.

[LaChab]

@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!

[Redbeard]

Ah... Are they inward-opening? I had assumed they were outward-opening, but I cannot find confirmation of that.

[Redbeard]

@LaChab, Google translate suggests that Rahmenaussenmass means 'external frame dimensions', suggesting (to me...) that that 85mm section is inside. But perhaps I am misunderstanding.

Edited 14 hours ago by Redbeard

[MikeSharp01]

 

17 minutes ago, LaChab said:

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!

Are they inward opening or outward is the large flat side on the inside then?

[Roundtuit]

37 minutes ago, LaChab said:

@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.

Pack the reveals a bit.  You may have to pack around fitting brackets anyway. Or use 15mm plasterboard + skim and take your time taping to be accurate.

[LaChab]

@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.

[LaChab]

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

[Redbeard]

• ''Posted 15 minutes ago (edited)

''@LaChab, Google translate suggests that Rahmenaussenmass means 'external frame dimensions', suggesting (to me...) that that 85mm section is inside. But perhaps I am misunderstanding.

Edited 14 minutes ago by Redbeard''

 

No, I got that completely ar*e-about-face!! @LaChab I think you must be right and I am wrong. So they are inward-opening?

[LaChab]

@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.

[Mike]

1 hour ago, LaChab said:

I've been told that installation is with Illbruck FM330, but no airtight tape.

Illbruck FM330 is very good stuff. If you have of suitable gap between the window and wall (at least 5mm - I prefer to aim for 7.5mm) fully filled with FM330, then it will be airtight. If that gap's too narrow to ensure full foaming, then it may not be.

 

If it is properly foamed, then whether you then need an airtight tape or not depends on the rest of the structure. For example if you have an internal VCL that needs to be sealed against the windows, then you may well need a tape to do that. But I think you're using ICF - so chances are it's not needed, but it depends on exactly where and how you're fitting the windows. We'd need a detail drawing / sketch of the window-wall junction to advise further.

[LaChab]

@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.