[jimbomaybe]

I was up in the attic area yesterday contemplating some electrical work, put my hand on the large flexible supply duct from the furnace ,it was surprisingly warm. The heating season is not the issue in Florida but insulation or lack cuts both ways, how much cooling energy is lost to the duct work in summer, would wrapping it with more insulation be worth the time , money and effort ?

[retiredguy123]

The flexible ductwork is already insulated by its design. It also provides a vapor barrier. You would not want to add an additional layer of insulation that would add another vapor barrier that could trap moisture between the two vapor barriers. It would also make it difficult to detect an air leak in the duct. Any benefit would be minimal. I would not do it.

[villagetinker]

I agree with the above, complete replacement with a higher rated duct MIGHT work, but is not going to be inexpensive.

[Toymeister]

OP since payoff and energy savings are your goal, I have great news.

Spend your money on the cheap easy fixes to get real savings. In duct work the savings are found at the joints, both the junction boxes and at the ceiling penatrations. Your installer used duct mastic or foil sided 'duct' tape. The did the junction boxes in a rush and probably missed several areas, and none at all at the penatrations. Your can lights, which have a high heat shut off built in, are a huge energy waster. Any light tubes are not sealed at the ceiling.

Look to these areas for savings and cleaning your evaporator coils on your outside ac unit. That costs only the water to spray it down.

[Altavia]

I've witnessed this make a huge difference in leakage reduction, payback would be very system dependant.

Aeroseal - Leak Sealing for Clean Air, Comfort, Energy Savings

Injected Spray Sealant for Existing HVAC Ducts | Building America Solution Center

[retiredguy123]

If you want an energy saving DIY project, and you can access your attic, add an additional 6 to 12 inches of blown-in insulation over the entire attic space above the conditioned areas. But, don't block the eave vents.