Install a Flexible Duct Branch to a Supply Register

A. Finished-Project Specification

Quantity: one flexible-duct branch per assigned register, installed at the approved diameter and route, connected and sealed at both the takeoff collar and register boot, supported at the specified spacing, insulated per the approved system, and verified under airflow.

B. Component Schedule

Component	Quantity	Material	Finished Size	Preparation
Flexible duct	1 length per branch	Listed insulated flexible duct per approved design	Approved diameter; cut to extended installed length	Extend fully before marking cut line
Inner-liner clamps	2 per branch	Listed clamp or draw band per manufacturer instructions	Sized to collar diameter	Positioned at manufacturer-specified engagement point
Duct mastic	As required for 2 connections	Listed duct mastic compatible with liner material	Applied to specified thickness	Surface cleaned and dried before application
Support straps	Per approved spacing	Wide approved strap material	Sized to duct diameter without compression	Installed at specified spacing intervals

C. Material Takeoff

• Duct materials: one length of listed insulated flexible duct per branch, sized and lengthed to the approved design plus manufacturer-required slack for extension and bends.
• Connection materials: two listed clamps or draw bands per branch, duct mastic, and listed HVAC foil tape for both liner connections.
• Support materials: wide approved straps sufficient for the full route at the specified spacing.

D. Fastener and Hardware Schedule

Joint	Fastener/Hardware	Installation Direction	Final Seating Condition
Liner-to-collar	Listed clamp or draw band per manufacturer instructions	Positioned over the manufacturer-specified engagement zone	Tightened to manufacturer-specified position or torque; no liner slip when pulled by hand
Liner-to-boot	Listed clamp or draw band per manufacturer instructions	Positioned over the manufacturer-specified engagement zone	Tightened to manufacturer-specified position or torque; no liner slip when pulled by hand
Outer jacket closure	Manufacturer-specified closure (tape, drawstring, or clamp per product)	Applied over insulation covering the sealed liner connection	Continuous closure with no gaps in vapor facing
Support strap	Wide approved strap fastened per manufacturer instructions	Perpendicular to duct axis at marked support points	Snug without compressing insulation; duct level or sloped per design

E. Reference Conventions

Reference end: the takeoff-collar end of the branch. Reference direction: airflow travels from the takeoff collar toward the register boot. Top: the upper surface of the duct as installed, used for identifying sag. Long-radius bend: a bend whose radius does not reduce the duct's internal diameter or crease the inner liner.

F. Acceptance Standards

Check	Standard
Diameter and length	Match the approved design; no field substitution
Liner connections	Full manufacturer-specified engagement, clamped, and sealed at both ends with no visible gap
Jacket closure	Continuous vapor-facing closure with no gaps over each sealed connection
Support spacing	Matches the approved design or manufacturer maximum spacing; no unsupported span exceeds that limit
Sag	Does not exceed the manufacturer-specified maximum sag between supports
Bends	Long-radius only; no kinks, crushing, or sharp offsets
Airflow test	No collapse, audible leakage, excessive vibration, or register underperformance during the authorized test

G. Preparation, Design Confirmation, and Access

1. Review the approved duct diameter, length, route, takeoff, boot, bend limits, support spacing, insulation, and closure system. Record each value on the Branch Specification Record before proceeding.
2. Confirm that the branch size and route are provided by the approved design. Do not proceed if any required value is missing; obtain the corrected design first.
3. Shut down equipment and verify safe access. Use the Project 2 procedure and confirm the blower cannot start.
4. Inspect the route for sharp edges, heat sources, moisture, structural restrictions, and other utilities. Stop work if an unidentified condition is found and it was not accounted for in the approved design.

H. Layout and Support Marking

1. Mark support points and maintain the shortest practical approved route. Use the marker to identify each support location along the route.
2. Measure the installed path without adding unnecessary excess length. Record the measured path length against the approved maximum length.

I. Cutting the Flexible Duct

1. Extend the flexible duct to its intended length before final cutting. Stretch the duct fully along the marked route or on a flat surface of equivalent length.
2. Cut the outer jacket and insulation without damaging the inner liner. Use the duct-rated shears or knife and cut only through the outer layers at the marked point.
3. Cut the inner liner square using the approved tool. Make a clean, square cut so the liner engages the collar or boot fully around its circumference.

J. Inner-Liner Connection at the Takeoff Collar

1. Slide the inner liner fully over the takeoff collar to the required engagement. Confirm the liner reaches the manufacturer-specified engagement point before clamping.
2. Secure the liner with the listed clamp, draw band, or fastening system. Position and tighten the clamp per the manufacturer instructions in the Fastener and Hardware Schedule.
3. Seal the inner-liner connection using approved mastic or listed tape. Apply the mastic or tape completely around the connection with no gaps.

K. Jacket Closure at the Takeoff Collar

1. Pull insulation over the sealed connection without gaps. Confirm the insulation fully covers the sealed liner joint.
2. Secure and seal the outer jacket using the specified closure. Apply the manufacturer-specified closure method to maintain a continuous vapor facing over the connection.

L. Repeat Connection at the Register Boot

1. Repeat the connection at the register boot. Perform the same liner engagement, clamping, sealing, insulation coverage, and jacket closure steps described in Sections J and K at the register-boot end of the branch.

M. Support, Bends, and Route Protection

1. Support the duct using wide approved straps that do not compress the insulation. Install straps at each marked support point.
2. Maintain the specified support spacing and maximum sag. Verify spacing against the approved design or manufacturer maximum before continuing.
3. Form long-radius bends and avoid kinks, crushing, sharp offsets, and contact with damaging surfaces. Adjust the route at each direction change to preserve the duct's full internal diameter.
4. Keep the duct off the ground and away from water or pest exposure. Confirm supports hold the duct clear of any wet or contaminated surface along the route.

N. Restoration, Airflow Test, and Correction

1. Restore equipment. Reverse the Project 2 shutdown procedure and confirm normal startup.
2. Inspect the full branch under airflow for collapse, movement, leakage, vibration, and excessive sag. Walk the full route while the system operates and note any deficiency.
3. Verify register airflow using the approved comparison or measurement method. Confirm delivery at the register matches the expected result for the approved design.
4. Correct support, bend, or connection failures. Re-isolate power or shut down equipment before making any correction, then repeat the affected steps.
5. Document route, length, supports, closures, and inspection results. Complete the worksheet before considering the branch finished.