I have central air and while the first floor gets comfortably cool, the second floor doesn't. My house is a two-story colonial with basement and attic in northern Massachusetts. The vents for the first floor are in the floor and come from the basement. The vents for the second floor are in the ceiling and come from the attic. Putting my hand up near a second floor vent, I can feel cool air coming out at what seems like ok pressure (my uneducated guess).
Now it seems to me that there are probably several factors at work here. One is that the cool air coming out of the second floor vents goes under the doors and down the stairs. To combat this, I got some of those bead-filled "snakes" (or whatever you call them) to block the space under the door. I also hung a curtain across the hall at the top of the stairs. Together these things seem to help a little, but not nearly enough.
Another aspect of the problem is that it seems like not enough hot air is being removed from the second floor. There's a return vent in the second floor ceiling and it's about 1 sq. ft. The return vent in the floor of the first floor, however, is about twice the size and seems to pull in much more air than the second floor return does. The first floor return is practically right on top of the furnace, less than 5 ft. away.
Where the main vent comes out of the top of the furnace, it splits into two, one for each floor. In the one that goes to the first floor, there's a lever. The two ends are marked open and shut and it's variable in between. When I set it to shut, it seems like the air pressure coming out of the first floor vents is a little less, but I can't make any kind of accurate measurement.
Also, I don't know if this is related, but today I noticed a little water on the floor near the furnace. Should I be worried?
Back to the main question: what kinds of things can be done in a case like this? (I'm not looking to DIY--this clearly isn't my area of expertise.) Am I more likely to be happy calling a professional or just getting a couple of window units for the second floor rooms I use the most? If I call a professional, what are they likely to do and what do I want them to do? Is zoning the answer?
Let me know if you need more info, of course. Thanks for any advice.