One of the hardest parts to properly make a house airtight is making the air control layer absolutely continuous: to go around the drawing and through every detail without picking up the red pen. This is especially true at the 3 dimensional connections of inside corners, which don’t necessarily announce themselves in 2 dimensional drawings.
At an inside corner, where three airtight components are coming together is tricky because it is awkward to get tape to adhere effectively. However simple you detail your building, these corners will occur at your windows and will need to be dealt with.
The primary reasons that airsealing tape with multiple release strips are made is to address inside corners. The multiple release strips allow you to adhere the tape in corners in a step-by-step process. And the release papers made for these tapes are extra strong, so they won’t tear while being pulled from odd angles and in tight corners.
We have experienced, that the most effective way to deal with an inside window (or building corner) is to pre-make a TESCON Profil corner that can then be adhered to a window frame, see steps below. In the TESCON Profil application guide it is briefly mentioned in step 3a.
These pre-made pieces are to be used in each corner. To seal the window frames to your airtight layer use longer lengths of tape, this step is relatively easy and can be done before or after installing the corners – if the installation gap between the frame and your airtight-layer is larger than 1/8″ install the long stretches first. When installing these long pieces, make sure to end them as close to the corner as possible. If you installed the corner first, make sure there is at least a 1″ overlap of tapes. Making these overlaps will assure proper continuation and durability of the airtight connection you just made.
Using this technique assures that the airseal in these hard to reach spots will be durable, tight, free of creases and should thus prevent frustrating leaks to appear there during the blower door test.