Ductwork Insulation
CSI Division 23, HVAC
Insulation wrapped around or lining a building's HVAC ductwork, applied for two distinct reasons depending on the duct, energy efficiency on supply ducts running through unconditioned spaces, and condensation control on ducts carrying cold air through warm, humid spaces, where an uninsulated duct's cold surface would otherwise sweat.
Why it matters
Insulating a cold-air duct without also managing the vapor barrier around that insulation can make condensation worse rather than better, moisture still reaches the duct's cold surface through a gap in the vapor barrier and gets trapped against it, so the insulation and its vapor barrier have to be installed as one continuous, sealed system.
On a real project
A sheet metal contractor wraps supply ductwork carrying chilled air with insulation that includes a continuous, taped vapor barrier at every seam and joint, preventing humid ambient air from reaching the duct's cold surface anywhere along its run.
Who this matters most to
A Sheet Metal Worker fabricates and installs ductwork, often coordinating with a separate insulation crew who wraps it once it's hung.
Where this goes wrong
An insulation crew wraps a cold-air duct but leaves several sections of the vapor barrier untaped at the seams to save time. Humid air reaches the duct's cold surface through those gaps, and condensation drips from the ceiling below within the first humid season, requiring the insulation to be removed and reinstalled correctly.
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