I have a two story brick home built in 1970 with a relatively new HVAC system blowing through original ductwork. In the summer its too hot upstairs and too cold downstairs. I know that the full solution is to rework the ducts and introduce a second zone. This is not practical at this time.
I can often get the upstairs temps to be comfortable (mid-70's) by simply forcing the fan on and closing vents in unoccupied rooms. When I do this the temperatures downstairs will drop to the mid-60's. At night this actually makes the entire house too cold to be comfortable. There is also the added cost of having the blower run all the time.
If it matters I work from home. I am here all day so summer comfort is important.
Is there an intermediate fix I can make until I have saved enough to go to a two-zone system?
Can I install a second thermostat? A smarter thermostat?
Are there any vent opening/closing tricks I can try?