Julie, You have a zone problem. As I understand it you have a forced Air system that has only one heating and cooling unit. 1/ you can install a new unit on each level with its own thermostat. 2/ you can as Henry said close off the up stairs vents. This may help some. 3/ you can as I did close off one of the floors and install the electric baseboard heater in each room of the lower level. It works very well for me because I can turn on or off each room of the downstairs level as I wish. I'ts not to costly. You'll save enough on the heat bill over a short time to cover that cost. I still use the forced air upstairs as necessary. 4/you can have zone control valves installed in the duct systems which will allow one heat/air to operate with either level. With each level having its own thermostat.