I am in the middle of a complete main floor bathroom gutting and re-finish job in my house in CANADA.. and WINTER IS COMING!!!!
THE BACKGROUND (pics below):
My bathroom is 5'x 13' in a bungalow with 2x6' outside construction walls with Fiberglass batt insulation in the walls, and blown cellulose insulation in the attic. My house has been a very energy efficient and almost perfectly sealed home built in 1985.
I consider myself to be well versed with applying the proper rated vapour barrier to the outside walls using proper vapour-barrier/acoustic sealant (black tar of death) and stapling properly to have a PERFECT air-tight vapour barrier against our crazy -40C/F winters.. I even know about the Tuct-Tape work required to seal joins and overlap edges of separate sheets of poly, etc.
... However.. when I took down the old popcorn drywall ceiling (after i moved over all the cellulose insulation so it wouldn't fall in).. I noticed the original vapour barrier was ONLY stapled up to the rafters with the 5/8" drywall screwed/nailed through it... the bathroom ceiling vapour barrier had NO BLACK sealant along the edges, so it was not 100% air/vapour sealed to the attic.
Since i'm NOT doing popcorn ceiling again, should I apply black-sealant as well to the ceiling sheets of vapour barrier just like I will do to the outside wall to create a perfect seal??
I have read some stories that because proper attics (like mine is) has natural air-flow its OK for a small amount of warm-air to get into the attic because the natural airflow will vent the moisture!! Is this TRUE? or would i be creating a condensation disaster in the making?
Pic of outside wall with new vapour barrier ONLY sealed at top for now
Another close-up pic of the opposite corner showing exposed attic