ARI, The sealing system round windows and doors creates a great problem. In the old days there was a gap between the window liner, and the frame, other than wedges with a scriber on the outside. Today under the latest rules we have a 10 mm gap between the liner and the frame that gets filled with gap filler, which creates a suction in its self, plus a capillary reaction. The people making the rules never went to night school like we old timers did, and know nothing about the science side of building. The mastic sealers have a short life read what it says on the tube sometime. macdunk