Most over-the-range microwaves can be converted to vent outside, improving air quality and keeping your kitchen free of lingering odors and excess moisture. If your microwave currently recirculates air back into the kitchen, upgrading to an external vent is a smart move—especially if you cook often or have a gas range.
While a professional installation can cost $300–$600, a skilled DIYer can tackle this project with the right tools and know-how. In this guide, we’ll walk you through the process step by step, from checking your microwave’s compatibility to properly routing ductwork for optimal ventilation.
Tools and Materials Needed
Here is a list of the tools and materials needed to route a microwave exhaust vent to the outside:
- Screwdriver
- Pliers
- Transition piece
- Ductwork
- Metallic tape
- Laser measuring tool
- Jigsaw
- Roofing tacks and sealant
- Cabinet-grade plywood
- Corner trim
- Primer and paint
Note: It is important to follow safety guidelines and regulations when installing or modifying any electrical appliance. If you are unsure about any of the steps, consult with a professional contractor or electrician.
Interior Steps
1. Rotate the Microwave Motor
Turn off power to the microwave by unplugging it or switching off the circuit breaker.
- Remove the access plate on top of the microwave, usually secured with screws or clips.
- Locate the fan motor inside the microwave and remove its mounting screws.
- Rotate the motor 90 degrees so it blows air upward toward the vent, then reattach it.
If your microwave doesn’t have a rotatable fan, check the manufacturer’s manual to confirm if external venting is possible.
2. Attach the Transition Piece
The transition piece connects the microwave to the ductwork.
- Choose a transition piece that matches your microwave’s exhaust opening and duct size.
- Align it with the exhaust opening and secure it with screws or clamps.
Some microwaves come with a built-in transition piece, so check before purchasing one.
3. Install the Ductwork
Cut openings for the vent in both the cabinet and ceiling.
- Use a jigsaw to cut holes in the top and bottom of the cabinet.
- Mark the ceiling location with a laser measuring tool before cutting.
- Inside the cabinet, seal duct connections with metallic duct tape to prevent air leaks.
For the best airflow, use smooth-walled metal ducting instead of flexible ducting.
Exterior Steps
4. Create the Roof or Wall Exit
From the attic, mark the vent location directly above the duct path. Cut a hole in the roof decking using a reciprocating saw.
5. Install the Exterior Vent Cap
Secure the vent cap to the roof or wall to prevent leaks and pest intrusion.
For a wall vent, install a cap with a backdraft damper to keep out cold air and pests.
On a roof, slide the vent cap’s flange under the shingles and secure it with roofing tacks and sealant.
Finishing Touches
To conceal the exposed duct, build a simple frame using wood studs. This creates a sturdy base for attaching a cover and ensures the vent blends seamlessly into your kitchen.
- Attach cabinet-grade plywood: Once the frame is in place, secure plywood panels over it using screws or nails. Cabinet-grade plywood provides a smooth, durable surface that’s easy to paint or finish.
- Add corner trim: Cover any exposed edges of the plywood with corner trim for a polished, built-in look. This step not only improves aesthetics but also helps protect the edges from wear and tear.
- Prime and paint: Apply a coat of primer followed by two coats of wall paint to match the rest of your kitchen. Using a semi-gloss or satin finish makes cleaning easier, especially in high-moisture areas.
These finishing steps help your vent cover blend seamlessly into your kitchen while maintaining a clean and professional look.
Testing the Microwave’s External Ventilation
After you’ve routed your microwave exhaust vent to the outside, it’s crucial to test it to ensure it’s functioning properly and venting outside correctly. Failure to properly test the microwave could lead to potential hazards such as carbon monoxide buildup, which can be deadly.
To test the microwave and make any necessary adjustments, follow these steps:
- Turn on the microwave and let it run for a few minutes. This will help to ensure the fan is working properly and the air is venting outside.
- Check the exhaust vent outside to make sure that air is flowing out properly. You should be able to feel the air coming out of the vent with your hand.
- If the exhaust vent is not working properly, check the ductwork for any obstructions or kinks. Remove these so the air can flow properly.
- If the ductwork is clear and the exhaust vent is still not working properly, check the fan motor to make sure that it is running properly. Replace the motor if it’s not running.
- Once you have made any necessary adjustments, retest the microwave to ensure that it is functioning properly.
Why External Venting is Important
External venting directs air, moisture, and cooking fumes outside instead of recirculating them back into your kitchen. This helps keep the space fresh, clean, and safe.
- Removes cooking odors. Smoke, grease, and strong food smells can linger for hours. A proper venting system sends them outside, preventing buildup in your kitchen.
- Controls moisture. Cooking releases steam that can lead to mold growth, peeling paint, and warped cabinets. Venting excess moisture outside protects your home.
- Reduces heat. Cooking generates heat, especially when using the stove for long periods. Venting hot air outside keeps your kitchen cooler and more comfortable.
- Improves air quality. Gas stoves and high-heat cooking release pollutants like carbon monoxide and nitrogen dioxide. Removing these contaminants helps maintain healthier indoor air.
- Extends appliance lifespan. Microwaves and range hoods that vent externally last longer since they avoid grease and moisture buildup, which can cause internal damage.
A well-ventilated kitchen is more comfortable, healthier, and better for your appliances.
Microwaves That Can Be Converted to External Ventilation
Not all microwaves are designed for external ventilation. Before making the switch, check the manufacturer’s guidelines to confirm that your model supports venting through a wall or roof.
The two main types of microwaves that can be converted are:
- Over-the-range microwaves. These units are mounted above a stove and typically have built-in exhaust fans. Most can be vented externally by connecting ductwork through the wall or ceiling.
- Built-in microwaves. Installed into a cabinet or wall cavity, some built-in models also support external venting through a properly routed duct system.
Converting a microwave vent to exhaust outside can be tricky, especially if ductwork needs to be installed or rerouted. If you’re unsure about the process, consider hiring a professional to ensure proper installation.
