Quote:
Originally Posted by opendoor
By that logic, vapor barriers essentially don't in building, unless you have a perfectly sealed glass box.
More commonly, the term is used for materials that are below 0.1 perms and are considered vapor impermeable for all intents and purposes. Poly sheeting fits that bill.
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Exactly - you never get a completely sealed building - ever. Even in high end construction, such as high rises, etc., you never get a perfect seal. The idea is to get it sealed as well as possible. Polyethylene may be ok in a house, or even some smaller wood framed commercial buildings or wood framed condos, but it isn't good enough for most other types of buildings. Even if the perm rating is low enough to be under 0.1 perms, would you use a polyethylene vapour ######er in a high humidity, high performance project like a hospital? Not a chance. As per my link in a previous post, polyethylene is still considered a vapour ######er even if it is below 0.1 perms. It just isn't robust enough to be considered a vapour barrier.
In my specifications, I make sure I distinguish how I call up the materials, whether they are vapour ######ers, air barriers, air/vapour barrier. Neither I nor any of my Architect clients would ever call polyethylene a vapour barrier.