Yes, it is possible to vent a range hood out through the roof. Venting a range hood through the roof can be an effective way to remove cooking odors, grease, heat, and moisture from the kitchen. There are a few factors to consider when deciding whether to vent a range hood through the roof or through an exterior wall.
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What are the benefits of venting a range hood through the roof?
There are a few potential advantages to venting a range hood through the roof rather than through the wall:
– Improved airflow and ventilation – Venting vertically through the roof provides better airflow as hot air rises. This can result in more effective ventilation and odor removal.
– Shorter duct run – In many cases, venting through the roof requires a shorter duct run than going through an exterior wall. Shorter ductwork can improve airflow.
– More options for ducting – With roof venting, there are often more options for where to place the ductwork without having to maneuver around walls, cabinets, etc.
– Gets odors farther away from house – Venting through the roof pushes odors farther away from the home before they are expelled. This can help prevent cooking smells from re-entering through doors or windows.
– Less visible exterior vent – A roof vent may be less noticeable on the exterior of the home compared to a wall vent.
What are the downsides of venting through the roof?
There are also some potential drawbacks to consider:
– More complex installation – Running ductwork through the attic and roof is often more labor intensive than through an exterior wall. It may require navigating around rafters and roof framing.
– Professional installation recommended – Due to the complexity, working on the roof, and potential for leaks, professional installation is highly recommended for roof venting.
– Leaks possible – Holes cut in the roof need to be properly sealed and flashed to prevent water leaks. Proper slope of the ductwork is also important.
– Access for cleaning and maintenance – Wall vents are more accessible for periodic cleaning. Roof vents are harder to reach.
– Exposed to weather – Roof vents and ductwork are more exposed to the elements like rain, snow, etc. Proper insulation is required.
– May look more obtrusive – In some cases, a roof vent can look more obtrusive than a low profile wall vent on the exterior.
How to Vent a Range Hood Through the Roof
Plan the route
The first step is to plan the route for the ductwork to run vertically from the range hood location up through the attic and roof. Consider the following:
– Shortest possible duct run – This improves airflow and ventilation power.
– Avoid framing members and utilities – Work around roof and floor framing like joists and rafters. Watch for electrical wiring or plumbing pipes.
– Minimize turns and elbows – More turns restrict airflow. Use 45-degree elbows when necessary.
– Determine roof location – Pick a location on the roof that is inconspicuous yet accessible.
– Calculate total duct length – Include vertical and horizontal runs. Try to stay under 35 linear feet.
Select duct material
6” or 7” metal round ductwork is commonly used. Rectangular ducts can also work. Options include:
– Galvanized steel – Most durable and rigid, resists dents. Bare metal conducts heat/cold.
– Aluminum – Lightweight and corrosion resistant, but dents more easily. Bare metal conducts heat/cold.
– Stainless steel – Durable, neutralizes odors. Costs more than other metals.
– Plastic/vinyl – Insulated, blocks cold/heat. Flexible but not as durable.
Insulate the ductwork
It is important to wrap or cover ductwork with insulation in unconditioned attic spaces. This prevents condensation from forming and also improves performance. Fiberglass duct wrap or flexible insulation tubing can be used.
Install roof cap and flashing
A roof vent cap is installed over the opening cut into the roof. The cap allows ventilation while preventing rain, debris, and pests from entering. A flashing kit seals the space between the roof and the cap. The specifics depend on the roof type. Proper slope is crucial for water drainage.
Seal joints and connections
All joints and seams along the ductwork should be sealed with aluminum HVAC tape or mastic. This creates a smooth interior for optimum airflow. Foil HVAC tape helps seal small gaps.
Connect to range hood
Attach the upper end of the ductwork to the outlet of the range hood. Secure with sheet metal screws and seal with tape.
Install make-up air (optional)
When venting a high-powered range hood, makeup air may be needed to balance air pressure in the home. This can be supplied with an inlet connected to the outside.
Test and confirm airflow
Turn on the range hood fan at full speed and hold a strip of tissue at the wall/roof vent to confirm adequate airflow. Make any necessary adjustments.
Key Considerations and Requirements
Here are some important factors and codes to keep in mind:
Duct type and size
– Use rigid round metal ductwork – Flexible vinyl duct can collapse and impede airflow.
– 6” diameter duct – Recommended for airflow up to 600 CFM.
– 7” to 10” diameter duct – For high performance range hoods over 600 CFM.
distances and lengths
– 30 to 35 feet max – Total length from hood to vent cap.
– 2 feet min – Height above roof surface.
– 10 feet max – Horizontal run in attic or roof.
Pitch and slope
– 1/4 inch per foot – Minimum slope of ductwork up toward roof vent. Allows moisture drainage.
Duct supports
– 6 to 10 feet – Recommended support intervals along vertical and horizontal duct runs using metal strapping. Reduces vibrations and sagging.
Make-up air
– Required over 400 CFM – Helps replace exhausted air and balances home pressure. Typically with a 6” inlet duct.
Roof penetration and flashing
– Must seal tightly – Prevents water entry, vermin, and air leakage.
– Flashing kit – Fits roof pitch. Seals shingles and directs water flow.
– Storm collar – Secures vent cap and flashing. Helps seal out water.
Building codes
– IMC and IRC compliance – Installation must follow International Mechanical Code for ducts, makeup air, etc and International Residential Code.
– Roof framing – Cannot cut rafters or trusses without approval. Blocking often required.
– Local permits – Building permits are often required for roof venting work.
Costs and Considerations
Several factors affect the installation costs:
Ducting
– Duct material – 6” rigid metal ducting costs $5-$10 per linear foot. Flexible vinyl is cheaper but not recommended.
– Insulation – Fiberglass duct wrap adds $2-$5 per linear foot.
– Elbows, supports – Approximately $20-$50 each.
Roof work
– Roof type – Simple shingled roofs are $200-$500. Tile, metal, and other roof types cost more.
– Flashing kit – $100-$300 depending on roofing type and pitch.
– Roof repair – Any repairs or replacements add cost. Matching existing shingles or tiles.
Labor
– Professional installation recommended due to roof work.
– $1000-$3000 typical range for venting installation labor.
– More complex homes with longer duct runs cost more.
Total typical range: $1500-$5000
Simple installations in homes with attic access start around $1500-$2000. Larger custom homes with premium roofing can run up to $5000 or more.
Conclusion
Venting a range hood through the roof can provide superior ventilation and odor removal compared to wall venting. However, professional installation is recommended due to the roof work. The total costs range from $1500-$5000 in most homes depending on duct run length, roof complexity, and local labor rates. Careful planning and compliance with ducting and roofing codes is crucial. For homeowners deciding between roof and wall venting, the pros and cons of each method should be weighed carefully.