I have a four story townhouse (Maryland), 2 zones and no basement. For the past several years the fourth floor is just plain unbearable during the summer months. My HVAC pro says the ac units (I have a gas furnace) are working fine, however it is just hot and humid on that level.
I tried closing the 3rd floor vents, with no noticeable difference. We added an extra return vent in the hottest room to try and increase the circulation. No help. We added some booster fans to the 4th level vents and that made a marginal difference.
Finally I got fed up and said "screw the HOA" and installed a window unit in one of the rooms and that of course made a world of difference for that room, though the rest of the level was still muggy.
I saw this 50 pint dehumidifier at Costco and stuck it in the hallway and noticed it made a big big difference. However the draining in this unit is a pain and the patented delonghi pump system broke after a week.
I've read getting a whole house system will be more efficient, but my question is where to put it? On the upstairs system where the humidity is the problem, or the downstairs system where it isn't?