In window units such as windows of double pane construction, problems frequently arise due to moisture build up in a peripheral gap between the sash and the window panes due to water forced in by wind-driven rain. Drainage holes are conventionally found in the window sill for draining this water externally of the window as it collects. During storms, winds of high velocity cause a zone of high air pressure on and adjacent the walls of buildings, relative to the air pressure within the buildings and relative to the air pressure within the sashes of windows located on said walls, particularly if said windows are snugly mounted. The interiors of the window sashes, such as extruded plastic or metal window sashes, are essentially hollow and contain recesses in which single, double and triple-glazed window panes are mounted by means of continuous resilient flanges. The high exterior air pressure thus in effect generates a partial vacuum within the window sashes which sucks up water as it flows down and across the exterior faces of the windows during storms to accumulate within the window sashes.
Various attempts have been made in the past to overcome such problems. An attempt at overcoming such problems is discussed in U.S. Pat. No. 3,636,660 issued Jan. 25, 1972 to Gerald D. Peterson. The window unit described in this patents includes a weep or drainage chamber in the lower sill with drainage passageways along the sill to permit such entrapped water to flow into the chamber. The window unit also includes air passageways from the weep chamber to the interior of the dwelling to minimize a spouting effect on the collected drainage water that might be caused by sudden wind gusts during a driving rain storm. However, such a structure may suffer from heat loss due to the leakage of air into the dwelling in which it is installed, particularly in cold northern climates.
It is desirable therefore, to provide a means for draining water entrapped between the pane and its resilient sealing means and for reducing the problem of spouting of such entrapped water, while at the same time maintaining an effective air seal with the interior of the room in which it is installed.
It is therefore an object of one aspect of the invention to provide a window or door unit having vent means for equalizing the pressure between the window or door sash sealing gap and the outside atmosphere while maintaining good thermal efficiency.
It is an other object of the invention to provide air pressure equalization throughout the sill, jambs and header in a sash member.