2. Advanced implementation

With the exception of the sill, traditional installation methods call for "single-stage" caulking, i.e. air and water tightness.

In addition, the positioning of joinery flush with interior linings requires the use of furring strips, creating an additional joint perimeter to be sealed.

It follows that the workmanship must be perfect, as the caulking is in the closed area. What's more, the caulking must not age or must be rigorously maintained, neither of which is the case in current practice.

The other approach is to create a "two-stage" joint around the entire periphery of the frame (see sketches 4 and 5...