I recently purchased a 1967 bi-level that has a heating/dampness issue in the lower level. During the summer, I close the ceiling ducts to prevent the air conditioning from coming directly into the rooms and run a dehumidifier. This seems to take care of the issue during the summer. In the winter however, the rooms never get warm. The dehumidifier runs and takes the dampness away even during winter. The lower level is around 650-700 sqft. The staircase is open. There are two cold air returns, one in each bedroom, I'm planning on adding one to the family room down there. Our son sleeps in the lower level and needs a space heater to keep it at a reasonable temperature in his room. The house has some insulation but I can't be certain how much. The exterior is brick and hardboard siding. What can be done to improve this heating problem? Booster fans in the room ducts to pull more heat to the cold rooms? More cold air returns? Attached a pic if its worth anything. Thanks for any help, just want to make the place more comfortable.