Each sash on the Next Generation Ultimate Double Hung locks directly to the jamb, so one can be opened while the other stays securely in place. Sashes are controlled via a single sweep mechanism and tilt in for easy cleaning. A vent mode lets the user lock the bottom sash open. A 3-by-5-foot pine unit with exterior aluminum cladding should be about $725. Marvin, 800.328.0268, marvin.com