• Know your true static pressure a real value
• R6 to R8 ductboard is less than 2f surface temp
• Seal attic – 110 cfm venting = 1 Gallon of moisture per hour
• Poor duct systems are popular. verify no air leaks and there is enough return air ducts
• Don’t use radiant barrier. It is good for utility bills but makes situation of duct sweating worse due to lowering duct temperature, must get surface temperature above dew point
• 24 Gallons a day, 18 per week = 970 BTU’s to remove 1 gallon of water per hour
• Zone 1 Lower Florida and Texas worse time for sweating is overnight June thru Sept overnights.
• Good to keep air handler off decking and away from wood by at least ½”
• Do not lay ductwork on air handler
• Venting attic is a terrible idea unless sealed from outside and use rafters as chase ways. 60% of the venting should be at the bottom and 40% at the top.bottom 40% top. Formula is simple 1 sq. ft. low opening for every 300 sq. ft. of floor space Closed cell foam seal best. Venting attic is terrible unless sealed from outside but, use rafters as chase ways.
• Hang air handler from metal supply duct on top but not lay on air handler cooler duct temperature, return below air handler.
• Sealing is best but must use closed cell foam.
• May or may not require a dehumidifies. if well sealed it should not

What you should not do, some things make situation worse.

• This will not be resolved by a phone call to your local HVAC contractor as a service call and create an unresolved labor bill. Most tech's will slow down the blower speed which may cause more moisture. It's about all they have to work with. They may check the refrigerant charge. If they do they should check the dict External Stat Pressure first to know the actual CFM of air.
• Do not add insulation around duct work.
• Add vents to the attic. This allows more moisture around the cool duct.