Insulating Ductwork In Attic

Scope install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords.

Insulating ductwork in attic.

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. Mechanically fasten and mastic seal all duct connections. The duct insulation should include a vapor barrier. Make sure the foil surface of the insulation is free of dust before applying the tape.

Sometimes the insulation is inside the ductwork. But if the floor is covered in plywood you can t stuff enough insulation beneath it to do the job sufficiently not even in warm climates. To insulate the exterior you have a choice between sleeve style insulation and blanket wraps which literally wrap around the ductwork. If necessary switch the wires to reduce the blower to its lowest.

A metal duct conveying cool conditioned air through a broiling attic in summer or warm air through a chilly crawl. To install sleeves you must either disassemble the ductwork and slide it on before reassembling the ducts or as many homeowners find themselves doing slit it and wrap it around like the blanket style material. 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. Flexible ductwork comes with different insulation r values.

Let s use your existing duct board surface that now faces the attic as an example. Because the moving air is in the ductwork for only a short period of time it does not need the insulation r value the attic floor requires. When insulating hvac ductwork use a foil faced fiberglass insulation with an r 6 or higher r value. Use a paintbrush to apply duct mastic to the joints where an elbow.

Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct. Use metal flex or fiber board ducts that are insulated to code. Check the speed of the blower motor on the furnace. Because the attic is hot it warms the surface of the duct board above the dew point temperature of the air in the attic.

Plan to pull up the flooring and layer new insulation on top of the old. Although both the attic floor and the ductwork are insulated ted recognizes the situation isn t ideal. Because the simplest and cheapest way to insulate an attic is to add material to the floor. Summer hasn t even arrived he notes in a post at gba s q a forum and when the temperature outside climbs to more than 95 f the temperature in the attic tops 120 f.

Use the type of metallic foil duct tape recommended by the insulation manufacturer to seal and hold the insulation in place.