Insulation Over Ductwork In Attic

What would be bad is if the duct work is flex duct and gets mashed under the weight of the added insulation on top of it.

Insulation over ductwork in attic.

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. If using this technique in a humid or marine climate the ducts must be encapsulated with spray foam before installing the blown insulation. Use the type of metallic foil duct tape recommended by the insulation manufacturer to seal and hold the insulation in place. For diy attic insulation you ve got two choices.

While in the attic inspect the insulation as well as the ducts. Snap a plastic cap onto the duct end then slip the preformed insulation over the duct. Both can be added to uninsulated attics or layered over existing material. Install loose fill insulation to cover the ducts and the attic floor to meet or exceed the code required r value for attic insulation.

Other times insulation may be on the outside. Once you ve decided which type is best for you examine the material options and prices to home in on the right product. Loose fill or batt the common term for blanket insulation. If we put ducts in unconditioned space they have to be insulated to either r 8 if they re in an unconditioned attic or r 6 in any other type of unconditioned space.

Have you ever considered the temperature differences delta ts across those different insulated surfaces. I found instead a vintage 3 ton ac unit with 1 rigid insulation taped all over it and insulated flex duct snaking all over the poorly insulated 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. No amount of duct insulating will compensate for an under insulated attic.

If the insulation is below the tops of the rafters it s also time to insulate. So more would help. 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. The duct work is insulated to keep the condensate from forming on the outside of the pipes and dripping off from the temperature differences in the attic in the summertime with ac running.

Sometimes the insulation is inside the ductwork. Chances are in an older home the insulation may be lacking. To install preformed duct insulation start by disconnecting an elbow to expose the end of the duct. When insulating hvac ductwork use a foil faced fiberglass insulation with an r 6 or higher r value.

The existing metal ductwork in an older home may or may not have insulation.