Warm edge is a type of spacer bar that by definition, has a warm edge! As opposed to standard aluminium bar which has a cold edge, But what difference does that make, you ask? In the home, varying conditions create moisture (see condensation page). This moisture in the air, in the form of a vapour, travels looking for an exit. When it reaches the window maintaining its vapourous state, it travels to the edge of the sealed unit near the frame, the cold surface caused by aluminium bar around the perimeter of the unit, turns the vapour back into moisture (water) and the result is condensation around the edge. Warm Edge technology has therefore been able to greatly reduce this natural process, by eliminating the presence of a cold edge.