How to Route Your Microwave Exhaust Vent to the Outside

Many times, you can convert an over-the-range microwave vent to exhaust to the outside.

A microwave is an essential appliance in most households, but installing one that vents to the outside can be a daunting task. However, with the right tools and knowledge, the installation process can be straightforward and stress-free. 

This article provides a step-by-step guide on how to route a microwave exhaust vent to the outside, or external venting, allowing you to upgrade your kitchen while keeping it safe and functional.

In This Article:

• Why External Venting is Important
• Microwaves That Can Be Converted to External Ventilation
• Tools and Materials Needed
• Steps to Convert a Microwave to External Venting
• Testing the Microwave’s External Ventilation

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Why External Venting is Important

External venting is the process of directing air, moisture, and other pollutants to the outside of the house instead of recirculating them back into the kitchen. 

Here are a few reasons why external venting is important in a kitchen:

1. Removal of Cooking Odors: Cooking odors such as smoke, grease, and other cooking fumes can quickly build up in the kitchen, causing an unpleasant odor. A proper external venting system removes cooking odors from the kitchen and directs them outside, ensuring that the kitchen smells fresh and clean.
2. Moisture Control: Cooking food generates a significant amount of moisture, which can lead to mold growth and other hygiene issues if not adequately controlled. A venting system removes this excess moisture from the kitchen, preventing the buildup of humidity and moisture-related issues.
3. Heat Control: Cooking also generates heat, which can be uncomfortable in the kitchen, particularly during the summer months. External venting helps to control the heat generated by cooking and directs it outside, keeping the kitchen cooler and more comfortable.
4. Air Quality: A venting system helps to remove pollutants such as carbon monoxide and nitrogen dioxide from the kitchen, improving the overall air quality in the house. These pollutants can lead to respiratory issues and other health problems if not adequately controlled.
5. Increased Appliance Lifespan: Appliances such as microwaves and range hoods that vent externally tend to last longer than those that are not. This is because venting helps to reduce the accumulation of moisture and cooking odors, which can cause damage to the appliance over time.

In conclusion, proper ventilation ensures that the kitchen remains fresh, comfortable, and safe for all who use it.

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Microwaves That Can Be Converted to External Ventilation

Not all microwaves can be converted to external ventilation. Before attempting to convert your microwave, check the manufacturer’s guidelines and specifications to ensure that the appliance is suitable for external venting.

Here are two types of microwaves that can be converted to external ventilation:

• Over-the-Range Microwaves: Over-the-range microwaves are mounted above a range or cooktop. They typically have built-in exhaust fans and can be vented externally through a duct that runs through the wall or roof of the house.
• Built-In Microwaves: Built-in microwaves are installed into cabinets or wall cavities. These microwaves can be vented externally through a duct that runs through the wall or roof of the house.

The process to convert a microwave vent to exhaust outside can be challenging, so you may want a professional to do it. It is crucial to follow the manufacturer’s guidelines and specifications and hire a qualified professional if you are unsure about the process.

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Tools and Material 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

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Steps to Route a Microwave Exhaust Vent to the Outside

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

Rotating the microwave motor

Turn off the power to the microwave by unplugging it or turning off the circuit breaker that supplies power to the unit.

Remove the access plate on the top of the unit in order to reach the motor. The access plate is usually held in place by screws or clips. If it’s held in place by screws, use a screwdriver to remove them. If it’s held in place by clips, use a flathead screwdriver to carefully pry them off.

Once you’ve removed the access plate, locate the motor mounting screws on the back of the microwave. Then, use a screwdriver to remove these screws, and carefully take out the motor.

Next, rotate the motor 90 degrees so that the fan motor now blows upward. This directs the exhaust up and out of the microwave, so it can vent to the outside instead of back into the room. Once you’ve rotated it, reattach it to the microwave using the mounting screws you removed earlier.

Attach transition piece

The next step is to attach the transition piece that will connect the microwave to the ductwork leading outside. Purchase a transition piece that matches the dimensions of the microwave exhaust vent and the ductwork or hood above it. Transition pieces are available in a variety of sizes and shapes, so be sure to choose the one that is appropriate for your needs.

Carefully align the transition piece with the exhaust opening on the back of the microwave, then use screws or clamps to secure it in place.

Attach ductwork

Using a jigsaw, cut a hole in the top and bottom of the cabinet so the duct can pass through.

To ensure that the hole in the ceiling is in the right location, use a laser measuring tool to mark a dot on the ceiling that identifies the center of the hole. This will make it easier to cut the hole accurately.

Inside the cabinet, use metallic duct tape to seal the joints between the transition piece and the microwave. This prevents any air from escaping through the gaps.

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Exterior Steps

In the attic, mark a spot directly above the duct so you can cut a hole in the roof decking. Use a reciprocating saw or other saw to cut a hole in the roof decking that is the same size as the ductwork.

On the roof, tuck the flange of a roof vent under the shingles above the opening and secure it with roofing tacks and roofing sealant. This will ensure the vent is securely in place and prevent any leaks.

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Finishing Touches

To hide the exposed duct in the kitchen, use wood studs to build a frame around the exposed duct. This will create a structure that you can attach the plywood to, and provide support for the cover.

Once the frame is in place, cover it with cabinet-grade plywood. This will create a clean, finished look and hide the ductwork from view.

To finish the cover, add corner trim to cover any exposed edges of the plywood. This will create a professional-looking finish that matches your kitchen decor.

Apply a coat of primer and two coats of wall paint to finish. This will give the frame a polished look and blend it into the rest of the kitchen.

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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:

1. 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.
2. 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.
3. If the exhaust vent is not working properly, check the ductwork for any obstructions or kinks. Remove these so the air can flow properly.
4. 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.
5. Once you have made any necessary adjustments, retest the microwave to ensure that it is functioning properly.

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Further Reading

• What Is A Home Warranty?
• The Best Home Warranties For 2020
• America’s Preferred Home Warranty Review