VCL guidance

[efunc]

 

 

This is my small 2m x 3m garden room. Originally I wasn't going to install a separate VCL and instead rely on fully taping up all my foil faced insulation. However the PIR boards I bought were second hand and many of them are pretty beaten up and punctured. I know it can still be done, but to do it really effectively as a VCL might require skill and patience I don't have. I will still have a go but now intend to follow up with some polythene VCL sheeting. Can anyone point me to some written or video guide for doing this, as I really don't know the technique. I also have some basic questions:

 

- I believe 1000 Gauge is usually advised, but in my case is 500Gu acceptable seeing as it's just a belt and braces thing over the Kingspan PIR? Something like this 125Mu roll from Wickes: Polythene Vapour Barrier. Is the thicker stuff easier to use and put up?

 

- Would you normally use a staple gun to fix it to the timber studs every 200mm? Or is it possible/better to use just a Double Sided Butyl Tape onto the studs and them stick the polythene down? 

 

- How do you deal with seams? Do you have to extrude both edges and fold them back down onto themselves and tape or staple?

 

- Finally, should I tuck the bottom of the VCL under that DPM under the screed and tape it down, or drop the VCL down over the DPM, or in fact fold both edges together and tape, as above?

 

I can't seem to find a tutorial about any of this, so if there is one, please point me in the right direction. Thanks!

Edited September 4, 2019 by efunc

[Onoff]

In my bathroom, similar size I used the green vcl from Screwfix (stock code 12869). That's only 300 gauge.

 

Did the ceiling first by laying the vcl on top of the pb:

 

 

I tried using double sided dpm tape but it was too thick on the one ceiling join - a couple of mm or more, so I ditched it and just used a black duct tape but I folded both edges back on themselves.

 

 

At the ceiling, that then comes down over the battens where I battened all the walls out.

 

 

My DPM comes up like this:

 

 

PIR then between the battens and vcl over the whole wall. Lidl Parside staple gun and No Nonsense spray adhesive.

 

 

Tbh I just foil taped all my joints:

 

 

Mine's more a nod to air tightness. I've somewhat shot that in the foot with so many ceiling penetrations; traditional downlighters, body dryer, speakers, occupancy switch. I am working on a plan to reinstate the airtightness around all these fittings but it's convoluted. With hindsight I'd have counterbattened the ceiling and stuck most of this stuff in the void, under the vcl layer.

 

Tbh everything is then plasterboarded and tiled. There ain't much air getting through them walls!

Edited September 4, 2019 by Onoff

[efunc]

That looks like a neat job, thanks. The double sided tape is about 4000 gauge, so I also wondered if the thickness would become an issue. But I think it's mainly for use joining sheets, not actually fixing them to all the framing like I was planning to do. I hadn't considered using something like No Nonsense spray adhesive though. Is that an instant grabber, or presumably it has to set?

 

I think I may have to pop down Lidl and see if they have any staple guns in their middle isle.

Edited September 4, 2019 by efunc

[efunc]

I've just found some other sheet I want to use (because it's clear), but it's not UV stabilised. Do you know if the one from Screwfix is UV stabilised, or if it matters? I know it won't see any light, but does it potentially go brittle anyway?

[Onoff]

15 minutes ago, efunc said:

I've just found some other sheet I want to use (because it's clear), but it's not UV stabilised. Do you know if the one from Screwfix is UV stabilised, or if it matters? I know it won't see any light, but does it potentially go brittle anyway?

 

Erm...if UV light makes it go brittle...and it won't see any...ergo it won't go brittle. 

 

Does say "prolonged exposure to sunlight will degrade the product"on the Capital Valley Plastics site.

Edited September 4, 2019 by Onoff

[efunc]

yeah, fair point.

 

I see that Capital Valley Plastics make that VCL in 500GU for a little bit more, so I might try that. Maybe it'll be easier to handle and keep flat:

https://www.trade-mart.co.uk/2-5m-wide-green-vapour-barrier-polythene-sheeting-500-gauge-125-micron.html