When installing a new range hood, one of the most important considerations is selecting the right type of vent pipe to use. The vent pipe carries cooking grease, smoke, odors, and other exhaust from the range hood outside of the home. Choosing the wrong material or size of vent pipe could lead to reduced efficiency and even safety hazards.
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Key Factors in Selecting Range Hood Vent Pipes
There are several key factors to take into account when selecting a vent pipe for your new range hood:
- Vent pipe material – The most common options are galvanized steel, stainless steel, and aluminum.
- Vent pipe shape – Round or rectangular/flat vent pipes are available.
- Vent pipe size – Match the size to the range hood CFM and length of run.
- Pitch – A minimum 1/4″ per foot upward pitch is recommended to allow grease drainage.
- Joints – Smooth interior joints are preferred to avoid grease buildup.
- Termination fitting – A wind-resistant roof or wall cap is required.
- Code compliance – Vent pipe must comply with local building codes.
Taking these factors into account will help ensure your venting solution maximizes air flow while also handling grease buildup and meeting code requirements.
Most Common Range Hood Vent Pipes
The three most commonly used types of vent pipe for residential range hoods are:
Galvanized Steel
Galvanized steel vent pipe consists of thin steel that has been coated with a layer of zinc to resist corrosion. This is an inexpensive and readily available option.
Key features of galvanized steel vent pipe:
- Low cost
- Easy to find
- Rigid
- Prone to rusting when exposed to grease and moisture over time
Stainless Steel
Stainless steel vent pipe is a premium option made from steel containing chromium to resist corrosion. It is more expensive but stands up well to grease and moisture.
Key features of stainless steel vent pipe:
- More expensive but long-lasting
- Corrosion-resistant
- Easy to clean
- Can last decades
Aluminum
Aluminum vent pipe is lightweight, naturally corrosion resistant, and easy to work with. It is more expensive than galvanized steel but cheaper than stainless steel.
Key features of aluminum vent pipe:
- Lightweight and easy to install
- Naturally corrosion resistant
- Relatively inexpensive
- Prone to dents and scratches
Round vs. Rectangular Vent Pipes
Vent pipes for range hoods come in either round or rectangular shapes:
Round Vent Pipes
Round vent pipe is the most common choice for range hood venting. It has the following pros and cons:
- Pros: Maximizes air flow, easy to find fittings, rigid
- Cons: Takes up more space, limited sizes available
Rectangular Vent Pipes
Rectangular or flat vent pipes allow fitting in tight spaces. The pros and cons include:
- Pros: More size options, fits in tight spots, takes up less space
- Cons: Reduced airflow, joints prone to leaks, less rigid
In general, round vent pipe is preferred for performance, while rectangular works well for fitting in small spaces if needed.
Choosing the Correct Vent Pipe Size
Selecting the proper vent pipe diameter is crucial for allowing optimal air flow and venting of smoke, grease, and odors. The key factors in vent pipe sizing are:
- Range hood CFM rating – Higher CFM models require larger pipes.
- Length of vent pipe run – Longer runs may need wider pipes.
- Number of elbows – More elbows increase resistance and need wider vents.
- Smooth or ribbed pipe – Ribbed has more resistance requiring wider pipes.
Always consult the range hood manufacturer’s venting recommendations for the model CFM rating. But in general, the following diameters are typical for common residential range hood CFMs:
| Range Hood CFM | Minimum Vent Diameter |
| 100-300 | 4 inches |
| 301-600 | 5-6 inches |
| 601-900 | 7-8 inches |
| 901-1200 | 8-10 inches |
| 1201-1500 | 10-12 inches |
When in doubt, go slightly wider rather than too narrow to ensure good airflow.
Special Considerations for Vent Pipe Runs
Properly installing and routing the vent pipes is just as important as selecting the right pipe itself. Here are some key considerations for vent pipe runs:
Maintain Upward Pitch
Maintain at least a 1/4″ per foot upward pitch when possible so grease will drain back to the hood. Avoid dips and low spots where grease can collect.
Minimize Elbows
Use as few elbows or bends as possible for maximum airflow. Each bend adds resistance and reduces venting performance.
Make Joints Airtight
Seal all joints thoroughly with approved tape or sealant to prevent grease leakage and maximize air flow velocity.
Support Properly
Support horizontal sections every 4-6 feet and vertical sections every 8-10 feet for safety and to avoid sagging or loosening of joints.
Clean Regularly
Inspect and clean vent pipes regularly, especially after a grease spill or fire. Burnt grease can build up and clog vents over time.
Choosing a Vent Pipe Termination Fitting
Proper vent termination is crucial to prevent backdrafts while also keeping out the elements. The main types of termination fittings are:
- Roof Cap – Standard for vertical roof terminations.
- Wall Cap – Required for horizontal sidewall terminations.
- 45 or 90 Degree Elbow – For directing vent through roof or wall.
The termination should have a built-in grease baffle to catch drips. Make sure to caulk around the termination to seal it to the roof or wall.
Key Code Requirements
Range hood venting must follow local building codes for fire safety and proper ventilation. Some key requirements include:
- Venting outside only, not into interior spaces or attics.
- Maintaining minimum clearances to combustibles.
- Not sharing ventilation with other systems.
- Using proper roof and wall terminations.
- Restrictions on concealed venting.
Always check local codes and get any required permits before installing. Many areas require range hood vents to be inspected.
Conclusion
Selecting the proper venting system for a new range hood involves many important considerations from material, sizing, routing, and termination. The vent pipe material should suit the budget while still providing long service life. Diameter must be matched to range hood CFM and run length. The system should be routed to minimize bends while still venting outside. And roof or wall caps must terminate correctly while sealing out elements. Following manufacturer specifications and local code requirements will ensure optimal, safe venting performance.