A fluorescent lamp with a thermally-insulating assembly includes an elongated glass tube. Mercury is disposed within the glass tube and a cold spot that substantially controls the vapor pressure of the mercury is present in the glass tube. One cathode stem is affixed to one end of the glass tube and extends into the glass tube a first distance. A second cathode stem is affixed to the other end of the glass tube and extends into the glass tube a second distance. The cold spot is located within a portion of the glass tube that is near the end of the glass tube where the second cathode stem is located, for example, immediately adjacent the end of the glass tube where the second cathode stem is located. A band of a thermally-insulating material substantially surrounds the portion of the glass tube where the cold spot is located and a jacket of a material capable of transmitting light substantially surrounds the glass tube.