Self-venting window frame

A frame structure incorporating an improved venting system said window frame structure including a plurality hollow frame pieces forming inside passages in said frame structure, drain holes interconnecting said inside passages to form a drain passage leading through said inside passages to a drain hole through said fame connecting said inside passages to outside of said frame, the improvement comprising a one way valve mounted on an inner wall of said frame in a position to interconnect said inside passage with the interior of a building in which said window frame is mounted said valve being oriented to impair flow into said building from said inside passage when air pressure in said inside passage is higher than air pressure in said interior of said building and to permit flow from said interior of said building to said inside passage when air pressure in said interior is equal to or higher than air pressure in said inside passage.