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A nylon draw band and tensioning tool are used to secure the inner coil of the pre-insulated flexible duct
A nylon draw band and tensioning tool are used to secure the inner liner of the pre-insulated flexible duct
A second layer of rigid insulation is installed over the 2 in. by 4 in. retaining strip
After securing the inner coil, cover the draw band and the seam with a generous amount of mastic
Air seal and insulate flex ducts
All other supply ducts and all return ducts in unconditioned space have insulation ≥ R-6
Assembled section of fiber board duct
Because this ICF and spray foamed house is so well insulated, the HVAC system is smaller, the round metal ducts are smaller diameter, and the duct layout is more compact.
Boot has been covered with insulation and sealed with mastic
Boot is uninsulated
Collars that are specifically made for flexible duct have a raised bead to prevent the duct from slipping off
Cut fiber board with a red V-groove tool and a gray shiplap tool to create mitered corners and a shiplapped edge for duct sections
Duct insulation is installed over boot
Duct is located in unconditioned space and is not insulated
Duct is located in unconditioned space and is properly insulated
Duct work is uninsulated and not sealed at seams
Ducts are insulated but strapping is compressing the insulation therefore reducing the R-value
Ducts are properly insulated and supported without compressing the insulation
Example of an HVAC installer’s balancing report form
Fiber board sheets are available with pre-cut shiplapped ends
Fiberglass duct board typically comes in sheets 4 foot wide by 10 foot long
Form a sheet metal shield around the flue pipe
Form sheet metal shield around pipe keeping 3-inch clearance
Hand tools for cutting fiber board sheets include a knife, straight edge, and color-coded edge-cutting tools
HVAC duct layout
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.
Install bottom layer of rigid insulation
Install wood framing cross pieces in the attic rafter bays on each side of the duct chase
Insulation does not cover boot and is not sealed
Open-cell polyurethane spray foam is sprayed on the underside of the roof for an R-28 thermal blanket of insulation that turns the attic into a conditioned space for the HVAC system while sealing out external allergens and pollutants.
Prescriptive Path: Supply ducts in unconditioned attic have insulation ≥ R-8. Performance Path: Supply ducts in unconditioned attic have insulation ≥ R-6
Pull the insulation and outer liner of the flex duct over the collar to come in full contact with the liner and insulation of the trunk line or fitting and tape in place
Right – Duct register is mastic sealed to framing
Right – Flex duct is mastic sealed at junction box
Right – Metal duct boot is properly sealed at seams
Right – Metal is mechanically fastened at junction
Right – Metal or fiberboard duct is mastic sealed at junction with duct register box
Right – Metal or fiberboard duct is mastic sealed at seams
Seal all joints and seams in the metal ductwork with mastic before installing insulation
Seal seams in fiber board ducts with out-clinching staples, UL-181A-approved tape, and mastic
Seams are being properly sealed with mastic and mesh tape
Several inches of spray foam lines the attic ceiling, sheltering the HVAC ducts from intense summer sun and providing a temperate storage area.
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.
Spray foam insulation used for raised ceiling duct chase
The attic is sealed and insulated along the underside of the roof deck with 5.5 inches of polyurethane spray foam, providing conditioned space for the HVAC system.
The HVAC system’s rigid metal ducting is installed between the floor joists rather than in an unconditioned attic or crawl space to minimize heat loss in winter and heat gain in summer.
The inner liner of the flex duct is fastened to the collar with a tension tie, the connection is sealed with mastic, then the outer layer is pulled over and sealed with mastic or foil tape (Steven Winter Associates 2013).
The main trunk line of the ducts runs within an insulated duct chase installed in a notch designed into the roof trusses that runs the length of the home to provide supply air directly to most of the home’s ceiling registers.
The sealed, insulated crawlspace is a clean, dry location to house the main floor heating ducts and also provides bonus storage space.
The tape is covered with mastic to ensure an airtight seal between the duct and the fitting
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.
To attach the flex duct to a main trunk duct or any other connection, the flex duct is pulled over the connecting collar at least 2 inches past the raised bead, then the insulation is pulled back
Trunk to duct connections are only mechanically fastened and not sealed
Trunk to duct connections are properly insulated and have been sealed with mastic
Two pieces of flex duct are spliced together with a metal sleeve, nylon draw bands, mastic, metal tape, and more mastic
Use only Underwriters Laboratory UL-181 approved tape
When wrapping metal pipes with insulation allow two inches of overlap and staple along the seam with outward clinching staples
Wrong- A tie strap should not be used over the duct outer liner because it can compress the insulation. Tuck in the fibrous insulation and seal the outer liner to the connecting duct with mastic or foil tape (Steven Winter Associates 2013).
Wrong: Blown insulation does not stick to raised duct chases
Wrong – Insulation not fully enclosing duct chase