Insulating Ductwork In Attic

Although both the attic floor and the ductwork are insulated ted recognizes the situation isn t ideal.

Insulating ductwork in attic. To insulate the exterior you have a choice between sleeve style insulation and blanket wraps which literally wrap around the ductwork. When insulating hvac ductwork use a foil faced fiberglass insulation with an r 6 or higher r value. If necessary switch the wires to reduce the blower to its lowest. Sometimes the insulation is inside the ductwork.

If you then put a layer of insulation over this surface this same surface will now begin to cool down. Use the type of metallic foil duct tape recommended by the insulation manufacturer to seal and hold the insulation in place. 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. The duct insulation should include a vapor barrier.

Acute temperatures in these areas contribute to thermal loss in metal ductwork. Use a paintbrush to apply duct mastic to the joints where an elbow. Because the attic is hot it warms the surface of the duct board above the dew point temperature of the air in the attic. 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.

Make sure the foil surface of the insulation is free of dust before applying the tape. Flexible ductwork comes with different insulation r values. Mechanically fasten and mastic seal all duct connections. Check the speed of the blower motor on the furnace.

Use metal flex or fiber board ducts that are insulated to code. 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. Plan to pull up the flooring and layer new insulation on top of the old. Let s use your existing duct board surface that now faces the attic as an example.

A metal duct conveying cool conditioned air through a broiling attic in summer or warm air through a chilly crawl. Scope install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords. 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. 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.

Other times insulation may be on the outside.