Go to Forum Home Building Design Air tightness – window/wall junction

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    • #31690
      A-tec Design

        I have a project on site, where the contractor has installed the windows using expanding PU foam rather than Iso Bloco One Tape. The resulting air permeability is 3.54.

        I know that no-one can be specific, but based on experiences, is the Iso Bloco tape substantially better at providing an air tight joint.



      • #38577
        Mark Siddall

          I have no experience of the tape in question. I would note that the use of foam raises a question about longevity. Foams shrink and become more brittle with age and as a consequence are vulnerable to movement. In the short term is the problem with foam is the size of the bubbles that can occur and the uncertainty about whether the void has been adequately plugged.


        • #38578

            Whatever you use I'd suggest getting a single unit fitted and checked before doing a whole building. From our experience it would have been much better to get a local contractor in along with the architect and window and tape reps to ensure they were all happy with the result rather than trust a “contractor that knows what they're doing” in and just let them do the whole install in one lump.

          • #38579

              Whatever you use I'd suggest …. From our experience it would have been much better ….

              Well said, Tahir. That's just the kind of feedback I hope to see on here.

            • #38580

                Dave has asked me to expand on my post so,

                We asked our Internorm reseller (EcoMerchant) to fit the glazing as we thought they would have an awareness of airtightness issues greater than that of a local glazing contractor. It turned out that they sub their fitting to a 3rd part firm, architect and builder had meetings with the the supplier and fitter to ensure that a fitting methodology was agreed prior to on site arrival of the glazing.

                The glazing turned up en masse and fitting commenced, the fitter just got on with it for a few days before the architect popped by to look at the job. The tape used was actually not adhering very well to the wall construction (OSB) resulting in layers and layers of the stuff, especially around corners, and plenty of sagging. After the first airtest we realised that this was quite a big deal so most of the windows were removed, openings retaped (with a different tape after visit from tape supplier) and then refitted. Far from satisfactory.

                In retrospect I think the main contractor's own chippies or glazing contractor with a day's training from the suppliers of tape and glazing would have taken things steadier and (probably) asked more questions of the site manager and architect rather than just fit everything and leave.

                This is based only on our own experience which involved a main contractor with a brilliant attitude to problem solving, a great architect (Jon Broome) and input from Alan Clarke too.

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