A window includes at least one multiple pane unit (1, 2) mounted in an opening for sliding movement between an open position and a closed position. The multiple pane unit (1, 2) includes at least two panes (34, 38) in spaced disposition, and has a seal (30) disposed there between to form a sealed chamber between the two panes. At least one of the panes (38) extends beyond the seal (30). In an alternative aspect of the invention, there may be two such multiple pane units (1, 2) in a sliding or other type of window. In the closed positions of the window, portions of the seal (30) of the multiple pane units are aligned and one of the multiple pane units (1) has at least one of its panes (38) extending beyond the seal (30).