Abstract: A hollow window frame structure is provided with a one way valve to permit flow from the exterior of the building to the interior of the building through the hollow frame when the air pressure is higher outside than in the interior of the building and impair flow from the interior of the building to the exterior of the building when the air pressure in the interior of the building is higher than the exterior pressure.

Abstract: An two-piece interlock for sliding window or door frame assemblies comprises a glazing bead secured to a sash frame for engaging a sealed glass unit; and an elongated seal having a T-shaped rail slidable to a limited extent within a longitudinal slot formed in the glazing bead. The seal extends between the sash frames when they are moved to closed positions. The glazing bead and seal on one of the sash frames together define an elongated slot for receiving a tongue formed on the other sash frame in the closed position. The sash frame carrying the glazing bead and seal is slidable to a limited extent relative to the seal to facilitate installation or removal of the sash frame from the outer window or door frame.