Insulating Ductwork In Attic

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.

Insulating ductwork in attic. If you then put a layer of insulation over this surface this same surface will now begin to cool down. Use metal flex or fiber board ducts that are insulated to code. If necessary switch the wires to reduce the blower to its lowest. 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.

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. Scope install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords. Let s use your existing duct board surface that now faces the attic as an example. When insulating hvac ductwork use a foil faced fiberglass insulation with an r 6 or higher r value.

Plan to pull up the flooring and layer new insulation on top of the old. Use the type of metallic foil duct tape recommended by the insulation manufacturer to seal and hold the insulation in place. Other times insulation may be on the outside. 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.

Acute temperatures in these areas contribute to thermal loss in metal ductwork. Check the speed of the blower motor on the furnace. Mechanically fasten and mastic seal all duct connections. Make sure the foil surface of the insulation is free of dust before applying the tape.

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. Sometimes the insulation is inside the ductwork. Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct. Flexible ductwork comes with different insulation r values.

Because the attic is hot it warms the surface of the duct board above the dew point temperature of the air in the attic. The duct insulation should include a vapor barrier. To insulate the exterior you have a choice between sleeve style insulation and blanket wraps which literally wrap around the ductwork. 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.

A metal duct conveying cool conditioned air through a broiling attic in summer or warm air through a chilly crawl.