My house is 15 years old, 3 BR about 2K SF. My upstairs is always too hot in the summer and too cold in the winter. We had an attic fan installed last summer which seems to help a little. It just seems like the air flow never makes it upstairs. So what could be a solution to my problem? How expense would it be to make the house dual zone? Does that mean having 2 A/C units installed and 2 furnaces? Is there also a solution to add dampers to the ducts to direct airflow upstairs? I'm looking for some suggestions. If more info is needed, please let me know. thanks!