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Insulation for rigid ducts comes in large rolls like this 4-ft x 50-ft roll consisting of a Foil-Scrim-Kraft (FSK) vapor barrier attached to the fiberglass insulation.

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The sealed, insulated crawlspace is a clean, dry location to house the main floor heating ducts and also provides bonus storage space.

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This is an example of an insulation pattern for rigid metal ducts that has been measured and cut in a comfortable location before being carried into the attic.

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HVAC ducts, cavities used as ducts, and combustion inlets and outlets may pass perpendicularly through exterior walls but shall not be run within exterior walls unless at least R-6 continuous insulation is provided on exterior side of the cavity

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This Habitat for Humanity builder ordered roof trusses with a 2-foot by 2-foot notch next to the center post then lined the cutout with rigid foam to form an insulated central duct chase to bring the heating and cooling ducts within the conditioned space.

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Tuck any extra vapor barrier around and under the insulation and pull it tight to the connecting duct or boot to create a firmer surface to apply tape.

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HVAC ducts can be encapsulated in 3 inches of closed-cell spray foam, then buried in R-49 of blown fiberglass insulation after the ceiling drywall is installed in the vented attic.

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Wrong – These flex ducts are pulled taut, which is correct but they are inadequately supported with straps that are spaced too far apart and are too tight causing pinching of the insulation and turns are sharp rather than gradual.

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A floor cavity between the first and second floor can provide a conditioned space for HVAC ducts if the rim joists are insulated and air sealed, if sufficient space is available, and if open-web floor joists are used

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Specially designed roof trusses come with a two-foot by two-foot notch cut next to the center post providing space to install an insulated duct chase inside the home’s conditioned space but above the normal ceiling height.

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The fiberglass insulation stuffed into the large hole around this HVAC duct will not prevent air leakage from the unconditioned basement to the conditioned space above; the large gap should be sealed with a rigid air barrier and caulked or spray foamed.

Fiberglass insulation stuffed into the large hole around this HVAC duct won't prevent air leakage from the unconditioned basement to the conditioned space above; the large gap should be sealed with a rigid air barrier and caulked or spray foamed.

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Encapsulated Ducts

Video

Video describing air sealing and insulation for encapsulated ducts.

Encapsulated Ducts

Guide

Guide that illustrates how and when to encapsulate ductwork in unconditioned attics, increasing the R-value of duct insulation, mitigating condensation issues, and reducing air leakage.

Diagram of buried ducts

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Jump Ducts

Guide

Guide describing how to install jump ducts in bedroom walls to balance air pressures between rooms, enabling stale air to return of the central air handler, even when room doors are closed.

Support at Intervals for Flex Ducts

Guide

Guide describing how to hang HVAC ducts with supporting straps or saddles to adequately support ducts so they do not sag and are not pinched or compressed.

Ducted Returns

Guide

Guide describing the use of ducted returns to return stale air from bedrooms and bathrooms to a central heating system.

Right – Metal or fiberboard duct is mastic sealed at junction with duct register box

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Ducts in Raised Ceiling Sections

Guide

Guide describing method for designing and installing ducts in a raised ceiling chase.

HVAC duct layout

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Ducts in Dropped Ceilings

Guide

Guide describing method for installing ducts in a duct chase in a dropped ceiling.

Sufficient Cavity Space for Flex Ducts

Guide

Guide describing how and where to install ducts, to ensure enough cavity space to avoid compression of the flex ducts or duct insulation.

No Excessive Coiled or Looped Flex Ducts

Guide

Guide describing how to correctly install flex ducts without excessive coils or loops.

Ducts in Interstitial Floor Framing

Guide

Guide for designing and installing interior ducts in an interstitial floor cavity in new and existing homes.

Burried and encapsulated ducts in a ceiling plane

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Collars that are specifically made for flexible duct have a raised bead to prevent the duct from slipping off

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Air Sealing Duct and Flue Shafts

Guide

Guide describing how to air-seal duct and flue shafts.

Duct work is uninsulated and not sealed at seams

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Sealing Duct Boots to Floor or Drywall

Guide

Guide describing how to air seal around duct shafts and flues installed through ceilings, walls, and flooring in new and existing homes.

No Kinks or Sharp Bends in Flex Duct Installation

Guide

Guide describing how to correctly install flex ducts without kinks or sharp bends.