4 inch Duct Intake & Exhaust Flanges (for damper)

4" Wall Pass-Through Duct Flange Set

This is a two-piece 4" wall pass-through flange designed for clean, professional duct installations through drywall, OSB, or similar wall materials.

The design uses four M5 bolts and nuts to clamp both flanges securely together, sandwiching the wall material for a rigid, airtight installation without relying solely on screws into the wall.

Features

• Designed for standard 4" ventilation ducting
• Two-piece flange system clamps securely through the wall
• Uses M5 bolts, nuts, and washers for a strong installation
• Large flange footprint hides rough wall cutouts
• Ideal for 3D printer exhaust systems, grow tents, workshop ventilation, and other low-pressure duct applications

Integrated Backdraft Damper Support

A key feature of this design is the integrated backdraft damper capture.

The internal geometry has been designed to securely retain a standard 4" backdraft damper between the two flanges. Clearance has been intentionally built into the model to allow the damper blades to swing freely without contacting either flange, ensuring unrestricted airflow while preventing reverse airflow when the exhaust fan is off. (damper used ASIN: B099KGNZRL). Any damper with OD of 97-101MM will work. 

This allows the damper to become part of the wall assembly rather than requiring separate mounting hardware.

Gasket Provision

The intake-side flange includes a recessed sealing surface that allows users to install adhesive-backed EVA foam or similar gasket material.

This creates a tighter seal against the wall, helping to:

• Reduce air leakage
• Minimize vibration
• Prevent rattles
• Improve the overall finished appearance

Recommended Hardware

• (4) M5 bolts (length depends on wall thickness)
• (4) M5 nuts
• (4) M5 washers (recommended)
• 1/8" (3 mm) EVA foam weatherstrip (optional but recommended)
• Standard 4" backdraft damper
• Standard 4" flexible duct and worm-drive clamps

This design was created for my own Bambu Lab printer exhaust installation to void VOCs and odors, but it should work well for many other 4" ventilation projects where a clean, secure wall pass-through is desired.