Vapour-permeable peel-and-stick
gf2011
| Posted in General Questions on
I’m getting close to the point where I need to turn the plywood sheathing of a double stud wall (which will be insulated with dense packed cellulose) into a proper air and water barrier. One approach I’m considering is to use Blueskin VP alone. Or should I consider taping the seams first?
Any concerns with using a vapour impermeable tape, such as 3M’s 8067? I’m somewhat restricted in the products I can use. Prosoco’s R-Guard system was my preferred approach, but didn’t get the green light from my building department.
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Replies
Graham,
Blueskin VP is an air barrier as well as a WRB. If you choose to install Bluskin VP, there is no need to tape the seams of your wall sheathing.
If you decide to use a different product as your WRB -- for example, Tyvek or Typar -- instead of Blueskin VP, then it makes sense to tape the seams of your wall sheathing to create a good air barrier. The tape you mention (3M All Weather Flashing Tape) performed well in my backyard tape test. For more information, see Return to the Backyard Tape Test.
I don't think that the vapor permeance of the sheathing tape makes much difference; after all, the tape covers only a small percentage of the exterior wall area. But if you are the type of person who worries about such things, you can purchase vapor-permeable tape (for example, Tescon Vana) from 475 High-Performance Building Supply.
Thanks for the helpful answer Martin.
I am reasonably confident that a good tape will stick for quite a long time - I'm not as sure about how well something like Blueskin VP will do over time. That's why I would tape first. Any sense about how well Blueskin will act in the longer term as an air barrier?
Blueskin will last very long time if not exposed to the sun.
If putting it on plywood, you'd need either to use a suitable primer and or
heat the membrane as it is applied and push-rolled .
If you arn't looking for a water barrier , using Blueskin all over is way overkill and costly.
Plywood makes a very fine vapor/air barrier if it is kept dry.
Also, peel stick rools have a much larger carbon/material impact than only using a few inches of tape.
Never used Blueskin--do you seriously have to prime first and then heat the product and roll it after application?
Having used a liquid-applied system (StoGuard) as the weather- and air-barrier for my house, I'm always wondering when (or if) others will jump on that bandwagon. Intuitively it seems like a very long-life product--certainly compared to tapes. And it seems like it would be easier to apply than Blueskin. As always, I'm all ears for data on comparative cost, longevity, effectiveness, and problems with LAWBs.
We use blueskin on valleys, around windows and doors. Never seen anyone prime or heat it. Maybe it would be necessary if you were doing the whole exterior?
Have you ever installed peel stick over plywood to cover very large portions ??
Unless it is full sun and 30c outside, get your heat fun ready.
Even acrylic "tuck tapes" benefit from a small amount of heat when the temperature is not ideal.
I've covered a few small buildings when doing some " REMOTE" type tests and installation,
and getting the peel stick to actually hold on plywood in large portion is tricky.
When your installation depends on this as vapor and air barrier, a portion that would "unstick" by itself on the ~north side of the building, unseen hidden under insulation , is not what you wish.
Anyhow, using peel stick all around a building is a good water and air barrier,
but might be completely unnecessary if you have another water management layer outside of it.
I still recommend to tape only the ply edges if possible.
Might save some labor and $$$ .
Also, additionally, i have found that using large rolls of peel stick
cut to required width ( lets say a few inches ) is usually much cheaper than buying the same width rolls of peel stick already cut.
In smaller width , it is very easy to apply with some heat and a light roller .
Jin, if you are using it as a complete exterior membrane, then doesn't that make it easier? One thing blueskin will stick to in any conditions is more blueskin.
Well detailing is much easier if it is used as a complete membrane,
but the area to install makes it hard to push it to stick evenly everywhere.
ahahahah ..it does stick to itself or tech tapes quite much :p
I'd like to test out the new 3d weather barrier membrane ... it is more expensive but uses acrylic based adhesive ( if i recall correctly ) and is transparent.
Non-perm versions of peel and stick WRB's are a bad idea, period. Wall and roof deck sheathing needs to release moisture outwards. Even if you have a dry-to-the-inside design, its a big risk to not have a way for vapor heavy air from escaping outwards. I would use the low-perm, not no-perm versions of Blueskin.
http://ca.henry.com/fileadmin/pdf/literature/airbarrier_brochure_web.pdf