SMA valve for controlling pressurized air supply to an air cell in comprising: a valve housing; a valve element (4) which is moveably suspended with respect to a mounting plate (30) in the housing between a closed position and an open position of the valve; a spring element adapted to exert a bias force on the valve element (4) to the closed position; a SMA wire (1) arranged such that shortening of the SMA wire upon exceeding its threshold temperature pulls the valve element to the closed position; a conductor (20) arranged on the valve element (4) in contact with the SMA wire (1) and arranged such that it comes into contact with a conducting surface (34) on the mounting plate (30) to close an electrical circuit when the valve element reaches its open position; a control unit arranged to supply electrical power to the SMA wire and to detect closure of the electrical circuit, and arranged to reduce the electrical power supply to the SMA wire when detecting closure of the electrical circuit, characterized in th
