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Green Building Bible, Fourth Edition
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Products: Velux - air tightness/thermal bridge (BBX, BFX, BDX)

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    • CommentAuthornikhoward
    • CommentTimeAug 16th 2012 edited
     
    Hello people,

    Has anyone ever used these, are they worth it? About to order the Velux's and is it better to use these rather than the traditional GB techniques of foam/silicone/Pro Clima tape to minimise air leakage and thermal bridge (without the debate of tapes failures, etc)?

    Any help/experience would be appreciated, some info on products below, thanks



    Insulation Collar – BDX

    • Insulates around the Roof Window frame, reducing heat loss and eliminating cold bridges.
    • Makes insulating and installing the window a simple process.
    • Comes with Underfelt Collar (BFX)
    • Made to all standard window sizes.
    • Click fittings ensure fast and accurate assembly.

    Underfelt Collar – BFX

    • Ensures a weather tight seal between Roof Window and the roof.
    • Can also be purchased separately from the Insulation Collar (BDX).
    • Pleated material ensures a flexible and tight seal to the underfelt of the roof, whatever its construction.
    • Made from diffusion open material to minimise risk of condensation.
    • Comes with transverse drainage gutter to lead water away from head of the window if a tile or slate is broken above the window.
    • Welded corners ensure watertight and simple installation.

    Vapour Barrier – BBX

    • Helps prevent condensation from forming in the roof construction.
    • Complete Vapour Barrier collar, fully welded in all corners.
    • A fully welded rubber gasket with double pressure seal guarantees speedy installation and a vapour and air tight solution.
    • Reinforced corners for extra security against perforation.
    • VELUX installation tool helps fit the collar in a matter of minutes.
    • CommentAuthorMikeRumney
    • CommentTimeAug 17th 2012
     
    Yes used first two of these when re-locating a velux dating back to pre their availabiliy ... and found them well made / easy to fit. Personally I would say your better off using the velux kit, but haven't tried the alternative you mention.
    (Also, see elsewhere on here for discussion of low level flashings that are "coming on stream" and attempts to bring the DG nearer to the inner face of the roof to reduce heat loss thru the frame ... )
    • CommentAuthorborpin
    • CommentTimeAug 17th 2012
     
    I'll be using them soon. Be aware you cannot link windows using BDX collars and the actual hole required is wider. I modified my design from a linked pair to 2 windows separated by 500mm. Velux TS is really good but make sure you ask the right question!
    • CommentAuthornikhoward
    • CommentTimeSep 2nd 2012
     
    Thanks guys, I was almost certainly going to use them, now probably definitely. Cheers,
    • CommentAuthornikhoward
    • CommentTimeSep 6th 2012
     
    Bump? (sorry to be needy)
    • CommentAuthorborpin
    • CommentTimeSep 8th 2012
     
    Not yet at the point of fixing them. They are on order too as are the 3G velux windows....
    • CommentAuthornikhoward
    • CommentTimeSep 9th 2012
     
    Doing ours at end of month
    • CommentAuthoraa44
    • CommentTimeSep 25th 2012
     
    I live up in Shetland where it's wet and windy and there are lots of Velux windows. I talked to my builders merchant to see what the local builders buy and the answer was none of them. As far as the underfelt collars are concerned, people seem to make their own out of breather membrane.

    I bought and used the underfelt collars for the windows that I installed last year. They were pretty easy to fit although, as we had an M08 window above an M34 fixed element, we had to cut the bottom off the underfelt collar for the main window and cut the top off the collar for the fixed element and then staple / tape them together at the sides.

    I haven't fitted the insulation in the roof yet so i don't know how I'm going to do the air tightness bit!
    •  
      CommentAuthorfostertom
    • CommentTimeSep 26th 2012
     
    Posted By: aa44i don't know how I'm going to do the air tightness bit!
    http://www.natural-building.co.uk/news/2010/files/SIGA-Airtightness-manual.pdf pp28-31
    • CommentAuthornikhoward
    • CommentTimeOct 15th 2012
     
    Well, there in, but can't say they are working yet, but quite easy to install. Whilst you could fashion your own, tbh I don't think it is worth it, would definitely use them again. Let me know if anyone wants any pics?
    • CommentAuthorwookey
    • CommentTimeOct 16th 2012
     
    Aren't they a rather feeble 15mm of PE foam, with corresponding wider flashing? A lot better than nothing but still pretty poor for what is a nasty thermal bridge in the roof. Of course without really wide flashings it's hard to do that much better, but we have discussed better designs here (mostly using fixed lights as it's hard to do much else if velux and co won't sell useful widths of flashing). I used the fakro equivalent insulated flashing, but did my own extra insulation around the timber under the tiles and inside. The roofers had never seen such a thing (insulation round roof windows).
    • CommentAuthornikhoward
    • CommentTimeOct 16th 2012
     
    Not perfect, but as you say a hard to treat area, the builders merchant says they hardly ever sell them
    • CommentAuthornikhoward
    • CommentTimeOct 17th 2012
     
    Posted By: nikhowardNot perfect, but as you say a hard to treat area, the builders merchant says they hardly ever sell them


    Have got the vcl/airtightness bits as well, which if you diyed it or got pro clima stuff would cost much more and/or be fidly
    • CommentAuthorborpin
    • CommentTimeNov 14th 2012 edited
     
    I have now fitted these and found them pretty good. http://www.borpin.co.uk/2012/10/13/slow-progress/ and http://www.borpin.co.uk/2012/11/10/nu-lok-roofing-system/

    Key thing I have learnt is that when fitting these on externally fitted insulation, just fitting them to the oversized counter battens works just fine. I had all sorts of ideas of building a wooden frame fitted through to the rafters but in the end we didn't bother. So there is virtually no thermal bridge except through the window frame itself. Sealing inside will be an interesting task. I think I should have used a breathable tape on the outside but I was not on sie when they were done and to be honest I have only just thought of it!

    Oh and the triple glazed Velux are heavy!

    (edit) In case you are wondering and have been following the saga, I ended up having Slate from Nu-Lok instead of the ceramic tile. These flashings are actually Tile flashings rather than the slate ones. Because of the fixing system it won't matter though.
    • CommentAuthorseascape
    • CommentTimeNov 14th 2012
     
    Looks like you're getting there - great pictures and info!
    • CommentAuthorCav8andrew
    • CommentTimeNov 15th 2012
     
    Great blog, very interesting re. Velux install and the Nulok roofing system, our chosen option (natural slate). Can really relate re. the weather. As a self build, me + incoming help you really need a sustained spell of dry weather for tackling the roof and we have just not seen it. We are still in a battened down state with tarps.
    • CommentAuthorborpin
    • CommentTimeNov 15th 2012
     
    thanks for the feedback :bigsmile:
    Posted By: Cav8andrewyou really need a sustained spell of dry weather for tackling the roof
    I wasn't too bad on that front. The PIR insulation once on is pretty weather tight and once the membrane was on even more so. Actually sunny dry weather (UV) would have been bad for the membrane as it sat for a while!

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