Millennium Home Design ThermaFlect double hung windows are made with the highest quality materials, producing resiliency and maximum energy efficiency in any climate. Double hung windows feature an upper and lower sash in a single frame which slide up or down to provide ventilation. The tilt in feature allows for effortless cleaning. The window systems are fusion welded with no screws or gaps thus improving performance and providing the most strength, integrity, and energy efficiency in vinyl replacement windows. Half screens are standard with the option of full screens.