Logistics & Installation · SOP
Rangehood Ducting Connection Seal
Standard procedure for properly sealing rangehood ducting connections using foil tape and mastic to ensure airtight performance and compliance with building codes.
Estimated Time
30 min
Difficulty
Intermediate
Regulation
CSA B365 / HVI
Version
1.0
Purpose
This SOP ensures consistent, leak‑free sealing of rangehood duct connections to prevent backdrafting, energy loss, and moisture accumulation. Proper sealing is critical for maintaining indoor air quality and meeting building code requirements for exhaust systems (CSA B365, HVI).
Scope
Applies to all residential and light commercial rangehood installations using 4‑inch or 6‑inch round ductwork. Covers connections between rangehood transition, intermediate duct joints, and wall/roof cap terminations. Excludes flexible duct runs and non‑ducted recirculating hoods.
Safety Precautions
- Ensure power to the rangehood is disconnected at the breaker. Apply lockout/tagout per company policy before any electrical or mechanical work.
- Wear safety glasses and cut‑resistant gloves when handling metal ductwork, cutting foil tape, or using a utility knife.
- Use an N95 respirator if applying solvent‑based mastic in an enclosed or poorly ventilated space.
Required Tools & Materials
- 4‑inch or 6‑inch aluminum foil tape (UL 181A‑P rated)
- Water‑based mastic (UL 181B‑M rated)
- Putty knife or small brush (for mastic application)
- Utility knife
- Magnetic duct connectors (if not pre‑installed)
- Tape measure
- Marking pen
- Clean rag
- Screwdriver (for damper assembly verification)
Procedure: Step-by-Step
1
Power Isolation — Turn off the rangehood at the breaker panel. Apply lockout/tagout per site safety procedures. Verify zero voltage with a multimeter.
2
Duct Inspection & Cleaning — Inspect the duct ends (rangehood transition, intermediate joints, and roof/wall cap collar). Wipe away dust, grease or moisture with a clean rag. Ensure the duct is dry.
3
Apply Foil Tape to Duct Joints — For each round joint, apply UL 181A‑P foil tape overlapping the seam by at least 50 mm (2 in). Press firmly around the entire circumference using a gloved hand or tape roller. Smooth out any wrinkles or air pockets.
4
Mastic Sealing (Optional – High Temp Zones) — If the duct run passes through unconditioned space or a chimney chase, apply a continuous bead of water‑based mastic (UL 181B‑M) over the taped joint using a brush or putty knife. Feather the edges to 25 mm beyond the tape.
5
Connect Duct Sections — Slide the male end of the next duct section into the previously sealed collar. Secure with 3 sheet‑metal screws equidistantly spaced. Tape or mastic the new joint as per steps 3–4.
6
Seal Transition to Rangehood — Attach the duct transition to the rangehood outlet using the manufacturer’s bracket. Ensure the built‑in backdraft damper opens freely. Seal the transition collar with foil tape, overlapping onto the hood surface by 25 mm.
7
Wall / Roof Cap Connection — At the termination end, connect the duct to the cap collar. Check the spring‑loaded damper for free movement. Tape the joint and apply a secondary mastic collar if required by local code.
8
Final Tape Pass & Inspection — Visually inspect every joint. Re‑tape any area with visible gaps or exposed screw heads. Use a smoke pencil or tissue to detect leaks with the fan running. Re‑seal any identified leaks.
9
Restore Power & Confirm Operation — Remove lockout/tagout, restore power, and run the rangehood on all speeds. Check for fan noise, vibration, and proper exhaust flow at the exterior termination.