Sometimes venting a range hood to the roof is the best option, especially if your kitchen hood is far from exterior walls and it's on the upper home level.
The toughest part of venting to the roof will be cutting the vent hole with a reciprocating saw.
And connecting the metal duct from the hood to the roof can also be a challenge, and we recommend adding insulation to the duct to prevent moisture and mold issues.
In this Home Inspector Secrets guide, I will go over…
- Our detailed 10 steps to vent your kitchen hood to the attic
- Why the bottom flashing of the roof cap should be free of roofing cement
- The importance of using custom roof vent caps (made out of metal)
- Using a reciprocating saw to cut the vent hole
- Insulating the duct to prevent moisture and mold problems
Let's get started on the 10 steps to vent a range hood to the attic...
What You Need To Know About Venting A Range Hood Through The Roof?
There are a few important considerations when installing a range hood to the roof:
Roof Hood Cover
For starters, you need to use a specially designed metal roof cap. These metal (not plastic) roof covers have backdraft dampers to keep out the exterior air, screening to keep out pests, and they are engineered to withstand the outdoor weather.
And always use an insulated duct when going through the attic. Unless your climate is warm throughout the year, you should wrap the duct in insulation to prevent condensation problems that can lead to mold or wood damage.
Please use a roof safety anchor if your roof is steep, very high up, or otherwise dangerous. These anchors are installed on the roof ridge, and it connects to you through a rope and harness. It can help prevent a fall and serious injury.
We Recommend A Roofing Pro
Unless you are really handy with these types of projects, going with a professional roofer is recommended due to the skill and danger involved when installing something on the roof.
Supplies You'll Need For Venting A Range Hood Through The Attic
- Reciprocating saw: You will use this to cut the vent hole on the roof through the sheathing. We recommend having a spare blade or two because asphalt shingles tend to chew up blades.
- Corded/Cordless Drill: You will need a drill to make the pilot hole in the roof sheathing. You may also need a drill to install screws into the metal ducting connections.
- Caulk Gun & Asphalt Roof Cement: You will need these tools to apply a bead of sealant underneath the flashing and shingles.
- Roofing Nails: Roofing nails have large flat heads and these nails will be driven into the corners of the roof hood (and covered with sealant).
- Roof Vent Cover: You will need a roof hood cover to do this project. These hoods are made out of metal and are designed to withstand the outdoor elements.
- Metal Ducting: You will need to connect the duct from the hood, through the attic, and attach it to the roof cap. The duct diameter is usually 4-6 inches (consult your manufacturer) and it should be made out of metal and have a smooth interior surface.
How To Install A Kitchen Hood Vent In The Roof? (10 Steps)
- Drill Pilot Hole in Attic
- Use Reciprocating Saw To Cut Hole
- Measure The Roof Cap 'Body'
- Cut And Remove Shingles
- Loosen The Shingles
- Dry Fit The Roof Hood Cover
- Apply Bead of Roofing Cement
- Nail The Corners of Flashing
- Apply Roof Cement To Underneath Shingles
- Connect The Duct
Step 1: Drill Pilot Hole In Attic
The first step is to drill a pilot hole into the roof sheathing from the attic. You want to use a drill bit that is large enough so that the reciprocating saw blade can later fit into it (to start the cut).
You also should first think about where you want your range hood to vent on the roof.
Ideally, you want the roof vent to be as close to the range hood as possible, and make the ducting as vertical as possible while minimizing any bends or turns. If you can keep any turns or bends to a minimum, it will maximize the airflow of the range hood.
Also, you don't want to install the roof vent too close to any other vents such as the ridge vent, passive vents, or attic fans. If it is installed too close, it will conflict with the airflow of the other vent.
Using your drill, work the drill bit entirely through the roof sheathing and shingles. You will need to be able to locate the hole or drill bit when you are on the roof.
Step 2: Use Reciprocating Saw To Cut Hole
Once you are on the roof, and located the exit point of the pilot drill bit, you can now use a reciprocating saw to cut the 4-8 inch circular hole. Always consult with the range hood manufacturer as to the size of the ducting required for that range hood model.
There is usually a short flange on the bottom of the roof vent cover, and this circular flange will go into the hole cut into the sheathing (and you connect the vent from inside the attic).
You can use this circular flange or a paper template to first mark the desired cut with a pencil (or with a utility knife).
After marking where you want to cut, insert the reciprocating hole saw in the middle of the pilot hole, and work your way out to the circle edge. It is also better to cut the hole too small than too large—you can always expand the hole if it is cut too small.
Make sure that the roof cutout doesn't fall into the attic and possibly into the attic insulation.
Read Also >> Is Venting To The Outside Necessary For Range Hoods?
Step 3: Measure The Roof Cap 'Body'
Now that you have your vent hole cut with a reciprocating saw, you will need to trace the square body of the roof vent onto the roof.
I am not talking about the flashing, but just the square body of the roof vent cap.
The upper half of the flashing will need to be inserted underneath the roof shingles which is why some of the roof shingles to the side of the vent hole will need to be removed (to make room for the square body).
Using a tape measure, determine the width of the body, and mark the width of the cutout on the roof. And now measure the vertical dimensions, and mark that on the roof as well.
Step 4: Cut And Remove Shingles
After you have marked the roof cap body, you will need to remove the shingles that are inside of the tracing, and surrounding the vent hole.
Simply take a utility knife and carefully cut the marking that you made and then remove the shingles.
Step 5: Loosen The Shingles
Once you have the circular vent hole cut, and removed the surrounding shingles to make room for the square vent body, now you need to loosen the shingles.
You will need to insert the roof cap flashing underneath the top row or two of shingles, so you need to break the seal of these shingles for it to work.
Remember: you only want the top half of the roof cap to be covered with shingles. The lower half of the flashing should be exposed. Simply take a pry bar or some other tool, working your way underneath the top half rows of shingles
Step 6: Dry Fit The Roof Hood Cover
Now that the shingles are loose (for the upper half portion), you can slide the top half of the roof vent cap underneath the shingles, while leaving the bottom half over the shingles and exposed.
Make sure that the roof cap fits properly and that the vent flange fits into the hole cut.
Step 7. Apply Bead of Roofing Cement
Once you have dry fitted the range hood, you will need to apply a bead of caulking underneath the upper and side flashing.
Don't apply the roofing cement underneath the bottom flashing. The bottom flashing needs to be clear of cement so that any moisture is able to drain out.
After you have applied the beads of roofing cement or caulk, carefully slide the roof cap underneath the shingles, and push it down to set it in place.
Step 8. Nail The Corners of Flashing
After you have applied a bead of roofing cement, you will need to nail the corners of the flashing with roofing nails.
Install at least one roofing nail in each corner, but you can always use more nails if you think it's needed.
We recommend starting first with the bottom two corners of the exposed flashing. And then carefully life up the shingles so you can put two nails into the upper corners. After nailing the flashing, apply some roofing cement to cover the nail heads.
Step 9. Apply Roof Cement To Underneath Shingles
As a last step, we recommend that you apply roof cement underneath the upper and loosened shingles just to keep them down.
Since you loosened these shingles, it is a good idea to apply some roofing cement as a finishing touch.
Read Also >> What Are The Steps To Install A ZLine Range Hood?
Step 10. Connect The Duct
Now you can simply connect the ducting from the range hood to underneath the roof cap.
Most roof vent caps have a 1-2 flange/collar that will be sticking into the attic where you can attach the duct. We recommend that you use smooth metal ductwork since flexible ducting has ridges that can capture grease and which may be a source of grease fires.
We also recommend that you insulate the vent hose inside the attic to prevent condensation and possible moisture (and mold) problems. The duct joints are also usually connected using aluminum foil tape and small self-tapping screws.
It's important to make sure that the duct is sealed in order to prevent particulate matter from building up inside the attic which can become a health hazard.
Final Thoughts On Installing Kitchen Exhaust Fans To The Roof
Venting a range hood to the roof can be a little challenging for the average homeowner, and there are definitely risks involved.
For most people, I would probably recommend having a licensed roof do this job, but if the roof isn't that steep, and if precautions are taken, it can be done in an afternoon.
The most difficult part will likely be cutting the vent hole with the reciprocating saw, as well as connecting the ductwork in the attic to the roof cap. It's also important to insulate the vent hose unless your climate is warm all year round.
I hope you enjoyed this guide, please leave a comment below to share your experience or if you have a question.