What Is a Smart Vapor Barrier? (and Why You Might Need One)
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- เผยแพร่เมื่อ 4 ต.ค. 2024
- Occasionally referred to as "smart vapor retarders", or "smart vapor control membranes", smart vapor barrier membranes allow vapor diffusion in one direction, but prevent vapor from moving in the other direction. This can be extremely useful to prevent condensation from occurring on the backside of the sheathing if you don't have the budget for rigid exterior insulation or closed cell spray foam.
Read the full article on how these smart vapor control membranes work: asiri-designs....
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*Read the full article on how these smart vapor control membranes work:* asiri-designs.com/resources-1/f/a-guide-to-smart-vapor-barriers
It's not allowing diffusion from one side and not the other. That would break the laws of thermodynamics, to push from low humidity to high humidity. It sounds like this membrane just changes permeability based on the temperature.
Close, it changes based on relative humidity, much like wood, but as you'd probably guess temperature is a big part of that equation.
If I installed it backwards, what would occur? Anything different? Thank you for the video.
Question .. Should the groove for the exterior horizontal tongue and groove cladding face up or down? I'd say up if water leaves by evaporation and down if it leaves by draining. Asking as I've always wondered and I see it's facing upwards in the drawing at 1:41. Thanks!
YEP! Good catch, looks like the profile got flipped.
Would Certainteed Membrain be a good product to use ?
Would applying this type product over top of Kraft faced fiberglass insulation ( 2x6 wall) help or is it redundant? Insulating a new barn. Wish I’d seen your video series sooner!
You’d be creating a vapor sandwich. You never want to use two
Hi, does this product seal around any mechanical fixing penetrations? If not its not going to be a great air barrier i assume once peppered with holes?
The membrane is taped at any penetrations to prevent air leakage, but in general we try to avoid too many MEP penetrations if we can help it.
@ASIRIDesigns thanks for the reply. In particular It's the staples and drywall fixing screws/nails penetrations that I am wondering about?
As long as your fastener penetrations hit the wood stud it is sealed. I use a product similar to this called Siga Majrex that is applied to the studs with a double sided tape that Siga also makes. So this way you only have the ten or so drywall screws per stud and anything that may be screwed to the wall over it such as cabinets after.
@@CMCraftsman thank you
@@markt8820 You’re welcome. The double sided Siga tape is called Twinnet and it’s extremely sticky so I would suspect that when you send a fastener into it, it probably seals around it pretty well much like an ice and water shield does around a roofing nail.
I have an external brick wall which I'm remodeling from the inside by tanking it with a two-component cementitious slurry and adding rigid 50mm 75 kg/m3 rockwool batts covered by double layer drywall installed on 30mm metal stud and track framing. Do I need this vapor barrier behind the drywall? The house in question is in a moderate continental climate, and I don't have the space for a service cavity unfortunately.
P.S. None of the stores or warehouses in my region seem to have a smart vapor barrier in stock. :( Choices I'm left with are traditional (polyethylene) vapor barrier and tar paper. Unless there is something else I could use? Perhaps swap the first layer of drywall with a 12mm (1/2") plywood or OSB (to serve as a vapor retarder) and attach a single layer of drywall onto it?
You’re better off not having a vapor retarder than having one in the wrong place. I think I would use the drywall as the air barrier in your case, being mindful when installing it to caulk the perimeter with something like big stretch and any joints before it’s taped
@@CMCraftsmanWhy would the interior side of the rockwool insulation be the wrong place to attach a vapor retarder?
P.S. What I have is (from the outside to the inside): Render -> 120mm/5" Brick -> 50mm/2'' cavity (rockwool + metal framing) -> Drywall. And I want to put the vapor retarder on the metal framing before screwing in the drywall.