air tightness

i was putting up some flashing tape along the band joist today; the asphalt self-adhered flashing (SAF) is covering the joints along the top and bottom of the band joist to form an air barrier.

the strip along the bottom edge of the band joist is attached to the rigid foam (attached to the exterior of the block foundation wall) and goes up along the edge of the sill plate, in over the 2" of exposed sill plate, and about 2" up the band joist. this seals the joints above and below the sill plate.

the strip along the top edge of the band joist is attached to the bottom edge of the wall sheathing and goes down and inward along the exposed 2" of bottom plate, then 2" down the band joist. this seals the joint between the bottom edge of the sheathing and the bottom plate, and between the bottom plate and the band joist.

this works; it forms an air barrier. it's also a pain to apply. i cut off a manageable length of about 5'-6' and then peel back a bit of one edge of the tape. i grab the exposed stickiness and bend it in half outward, so the opposite edges dont contact each other. i then carefully peel the rest of the tape, keeping it stiff, and immediately fold the other end in half and keep it stiff. if any of the sticky parts contact each other, it is almost impossible to fix. i then stick one end in place, hold the other end over where it will go, and slide my hand across, rolling the adhesive into contact.

anyway, this is a pain. slow, time consuming. rather expensive in tape. i'm using the most affordable SAF around here, but it comes with aluminum foil covering. i don't need a vapor barrier on the outside, although the inside is open so it can still breathe. it's just a pain, there are better ways to form an effective air barrier. this is just a solution to poor planning on my part.

i think SAF wouldn't be so bad if i had a high-speed applicator like the Zipwall products have, and if i were applying it to flat surfaces - not 3-dimensional corners like i'm working along.

better air barrier details next time..