Today s flexible ductwork is covered with a shiny metallic cover this is its vapor barrier.
Insulated ductwork for attic.
Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct.
In this video this old house plumbing and heating expert richard trethewey helps a homeowner insulate his ductwork.
The greater the temperature extreme between the air inside the duct and the air surrounding the ductwork the greater your need for duct insulation.
Unfortunately so many houses especially newer homes end up with ductwork running through the attic.
First consider the duct location.
Use metal flex or fiber board ducts that are insulated to code.
Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords.
When these ducts are exposed to exterior air the plastic jacket never gets cold enough to permit condensation because the hot attic air keeps the plastic jacket warm.
When hvac ducts are installed in a vented attic in a dry climate bury the ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space.
Check the speed of the blower motor on the furnace.
Most attic ducts are insulated flex ducts that is flex ducts with r 6 or r 8 fiberglass insulation along with an exterior polyethylene jacket.
Hvac ductwork is typically visible in your attic especially flexible ductwork.
The duct insulation should include a vapor barrier cover.
Covering ductwork with insulation.
Although both the attic floor and the ductwork are insulated ted recognizes the situation isn t ideal.
The shiny vapor barrier will protect the ductwork from sweating as long as it s exposed to the surrounding air.