Yes, insulate for comfort but the financial return on investment is low when the ductwork is in the basement.

Optimal improvement comes when you seal the leaks in your metal ductwork and then insulate the ductwork. The U.S. Department of Energy show an average leakage of 30-35% in most metal ductwork systems. That means that 1/3 of all heating and cooling is ineffective or lost in most American homes. This is potentially a very high return on investment for homeowners if they simply seal their ductwork systems.

Ductwork sealing is most effective when performed with duct sealing mesh-tape and sealing compound, which gets rather unsightly because it gets applied by hand at all the joints. Aluminum duct tape is another choice that is slightly less effective at sealing but more attractive. Insulate the ductwork by wrapping the metal ducts with Kraft-backed fiberglass blanket material and taping the wrap at the joints. Another method for ductwork insulation is to use duct-board which is a rigid fiberglass panel that gets glued to the ductwork in sheet form and gets taped at the joints. Duct board and duct wrap are commonly sold only at wholesale heating and cooling supply houses yet may be special ordered from hardware stores and home centers.

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