Ducting FAQ - Venting Your Range Hood

What size should my ducting be?
It is very important to make sure your duct size matches the ducting on your range hood. If your ducting reduces to a smaller size at any point, this will reduce the CFM output of your hood and make it much louder. The only time it is acceptable to reduce ducting is if your existing duct is larger than the duct size on the unit. Only in this scenario, it is okay to transition from the larger existing duct to the smaller duct on the range hood as this will not affect suction negatively.

How long should the ducting be?
For optimal efficiency your ducting should be as short as possible with minimal elbows. The longest your ducting should ever be is 50ft, but the shorter it is the more efficient your range hood will be. To calculate your duct length with elbows, please see the example below.

• Each 90 degree elbow = minus 9ft
• Each 45 degree elbow = minus 5ft
• Each round to rectangle transition = minus 7ft
• Wall/Roof vent cap with damper = minus 7ft

Example: 50 feet - two 90 degree elbows - Wall cap = maximum duct length of 25ft

If your ducting is long and/or has more than one elbow, we recommend using a duct bigger than 6" and a range hood stronger than 600CFM.

Where should I install elbows in my ducting?
You should never install an elbow within 12 inches of the range hood. If you have multiple elbows in your ducting they should also be at least 12-18 inches apart. The closer your elbows are to your hood and/or each other, the louder and less efficient your range hood will be.

What type of ducting is best for ventilation?
Range hoods should always be vented using metal ductwork. Smooth ducting is better than flexible or ribbed because smooth straight ducting won't reduce or restrict the airflow as much as a flexible duct will.

Always also make sure that your ducting never reduces down lower than the size the range hood comes with. For powerful hoods with more than 600CFM, you will need 8" round or larger ducting.

How do I make sure I have enough room for my ducting to vent out the wall behind my range?
The distance you will need for an elbow changes with each size. 6" ducting needs 9", 8" ducting needs 12" and 10" ducting needs 15". Once you know the desired height from the cooktop to your range hood, add the height of the hood (without chimney covers for chimney hoods) and the height of duct transition. All of our range hoods have their specific dimension diagrams available on the store page and in their manual.

Once you have found the very top of the where the exhaust from the hood fan will be, add the appropriate required space for the elbow and this is the minimum height your ducting should be from the floor. However we recommend elbows should be at least 12" from the top of your hood when possible.

There is no space for an elbow, can I duct into a fabricated box to connect the duct?
No, if you duct into a box or an open space this will completely kill the suction of your range hood and make it extremely loud. If you do not have space to install the ducting properly with your existing duct then we highly recommend replacing your ducting.

What is Make-up air?
Make-up air is additional air that you may require if you run a high-CFM hood often or for long periods of time. If you suck too much air out of your kitchen, it creates negative air pressure and will affect how your hood functions. To address this issue, purchase a make-up air kit that directs fresh air air from outside your home, which will recirculate throughout your kitchen.

Do you sell Make-up air units?
No, we do not offer any make-up air units. If you need make-up air or not sure if you need to install it, please contact an HVAC specialist

Do I need to install a separate vent for my range hood?
Yes. Most range hoods require a minimum 6" duct size.

What are the differences between ducted and ductless range hoods?
A ducted range hood requires a minimum 6" duct to the outside. Ductless range hoods typically recirculate the air within the kitchen and do not exhaust anything outside the home.

Can I use flexible ducting for my range hood installation?
It is recommended to use rigid ducting when possible. Flexible duct can be used in some cases, but it is not as effective and can cause more grease to build up over time.

How do I connect the range hood to the ductwork?
Ensure to seal and duct joints with aluminum tape.

How many bends or turns can I have in my ducting?
One or two duct turns maximum. Using more than two duct turns will increase static pressure and noise levels. Using too many turns will reduce CFM and suction as well.

How can I ensure my ducting is properly sealed?
Only use aluminum tape.

What are the benefits of using rigid ducting over flexible ducting?
Air travels smoother through rigid duct. This creates less friction, leading to a more powerful and quiet fan.

Can I vent my range hood through the wall or ceiling?
Yes, most range hoods can be vented either through the wall or roof. Please ensure to choose the correct model. Contact us for details if you require assistance at info@victoryrangehoods.com

What local building codes should I be aware of regarding range hood ducting?
The common ones are that the minimum distance between gas stoves and range hoods is 24" in most areas. Some building codes set a maximum allowable CFM. Please check with your city to ensure all your local codes are followed for your specific installation.