Insulating Ductwork In Attic

Check the speed of the blower motor on the furnace.

Insulating ductwork in attic.

Flexible ductwork comes with different insulation r values. 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. Plan to pull up the flooring and layer new insulation on top of the old.

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. Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct. Sometimes the insulation is inside the ductwork.

When insulating hvac ductwork use a foil faced fiberglass insulation with an r 6 or higher r value. The duct insulation should include a vapor barrier. 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.

Make sure the foil surface of the insulation is free of dust before applying the tape. Mechanically fasten and mastic seal all duct connections. 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. Although both the attic floor and the ductwork are insulated ted recognizes the situation isn t ideal.

Use the type of metallic foil duct tape recommended by the insulation manufacturer to seal and hold the insulation in place. 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. 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. Use metal flex or fiber board ducts that are insulated to code.

Let s use your existing duct board surface that now faces the attic as an example. Use a paintbrush to apply duct mastic to the joints where an elbow. To insulate the exterior you have a choice between sleeve style insulation and blanket wraps which literally wrap around the ductwork. Acute temperatures in these areas contribute to thermal loss in metal ductwork.

Because the attic is hot it warms the surface of the duct board above the dew point temperature of the air in the attic.