A valve (10) having a membrane (12) for controlling flow through the valve (10), the membrane (12) having open and closed positions. An element (14) urges the membrane (12) to the closed position, and a vacuum pressure at one end (18) of the valve (10) may overcome the urging of the element (14), thereby moving the membrane (12) to the open position. An actuator (26) is provided for easing or initiating the movement of the membrane (12). In some embodiments, the valve (10) may take the form of a a valve assembly for use in a variety of applications, for example, a valve assembly (30) for relieving a vacuum pressure wherein the assembly (30) includes intake (16) and exhaust ends (18), a membrane (12) for controlling flow through the assembly (30), a spring (14) providing a closing bias to the membrane (12) that the vacuum pressure may overcome to move the membrane (12), and an actuator (26) for initiating the movement of the membrane (12).