I live in N. central FL and have a question about humidity control. Back in Sep. I set up my AC (trane xl20i 3 ton w/ trane xv80) dip switches properly for a 3 ton unit at 350 cfm with Comfort-R enabled. The result was a huge improvement - the humidity dropped from as high as 70% down around 55% with the A/C running all day. I live in a shady area and now there is not as much cooling load. I have been running a portable 70 pint dehumidifier and just alternating which side of the house it is on - the humidity runs below 60% but moves up really fast when the dehumidifier is off. I know there is not one magic fix, but it would be nice to try to eliminate some of the problem. A whole house dehumidifier is not really an option since I don't own the house, and the owner seems to think that excessive humidity is just normal for FL houses.
1. I have only been running the dehumidifier for 2 weeks. If the house has been overly humid for years, will running a dehumidifier longer help with structural moisture (not sure if that's the right term) problems?
2. The house is a rental and I recently had some major holes (rot from moisture) repaired in the fascia board. Also, when I moved in a few months ago, I had to clean out a lot of leaves from the ridge vent. I am now wondering about the attic being a moisture source for the house. Is there a way to diagnose this (without expensive equip)? Should I try to actively dry out the attic if there's moisture present?
3. I have seen advice on sealing up the ductwork with mastic to prevent exchange with the attic, but I have also seen that a house sealed too well will have humidity problems. By sealing around the register openings in the ceiling, will I just make my problem worse?