4" Round Duct Adapter

The 4” Round Duct Adapter lets you redirect airflow from any standard floor vent to exactly where you need it. Connect a standard dryer vent hose and route heated or cooled air to cold corners, home offices, workshops, or anywhere your HVAC system doesn’t quite reach.

How It Works

The adapter features a tapered rectangular base that friction-fits into your floor vent opening, replacing the standard grille. The top transitions smoothly from the rectangular footprint to a 4-inch round opening sized to accept standard flexible dryer vent hose.

A raised ridge around the round opening provides a secure grip for the hose, and you can add a standard hose clamp for a completely airtight seal. The internal geometry is optimized for minimal airflow restriction.

Common Applications

Home Office Comfort: Route warm air directly to your desk in a basement office or garage conversion. Stop fighting with the household thermostat.

Workshop Heating: Redirect heat from an underused room to your workshop or garage. Combine with an inline duct fan for longer runs.

Humidity Control: Send dry, heated air to damp basements or bathrooms to reduce moisture without running a dehumidifier.

Pet Comfort: Create warm zones in pet crates or beds. Perfect for older pets who need extra warmth.

Grow Operations: Maintain optimal temperatures for seedlings or indoor plants without dedicated grow room HVAC.

Hose Compatibility

This adapter is designed for standard 4-inch (102mm) flexible aluminum or vinyl duct hose, the same type used for dryer vents. These are available at any hardware store for $10-20 for a 25-foot length.

For permanent installations, we recommend semi-rigid aluminum duct over the cheaper vinyl options—it maintains better airflow and is more durable.

Material Requirements

PETG is required for this print. Unlike the sheet fort clip which sees only moderate temperatures, this adapter is in constant contact with heated air and needs to handle sustained temperatures of 120°F+ (49°C+). PLA will warp and deform within days of use.

For even higher temperature applications (near furnace registers, for example), consider printing in ABS or ASA.

Installation Tips

1. Remove your existing vent grille
2. Press the adapter firmly into the vent opening—it should snap in with a satisfying click
3. Slide your flexible duct over the round opening
4. Secure with a hose clamp for airtight seal (optional but recommended)
5. Route the duct to your desired location
6. Consider an inline duct booster fan for runs over 15 feet

Airflow Considerations

A single 4” × 10” floor vent typically delivers 50-100 CFM depending on your HVAC system. The adapter’s smooth internal transitions preserve most of this airflow, but expect some reduction with longer duct runs.

For runs over 15 feet, an inline duct booster fan (available for ~$25-40) will maintain strong airflow. These plug into a standard outlet and can be controlled with a simple switch or thermostat.

Safety Notes

• Never completely block a vent—always ensure some airflow path
• Do not use with flexible vinyl duct near furnace registers
• Keep duct runs as short and straight as possible
• Inspect periodically for dust buildup in the adapter