Is it OK to vent your range hood into the attic?

Venting a range hood into the attic is generally not recommended. There are several reasons why venting into the attic can cause problems.

Moisture and Condensation

One of the main issues with venting a range hood into the attic is that it can introduce a lot of moisture into the attic space. Range hoods are designed to remove grease, smoke, odors, and moisture from cooking. All that moisture has to go somewhere, and an attic is not the right place.

When warm, moist air from the kitchen vent enters the attic, which is often cooler, the moisture can condense on the underside of the roof. This can lead to mold and mildew growth, rotting roof decking and rafters, and other moisture-related damage. The attic needs to be properly ventilated to allow that moisture to escape.

Grease Buildup

Range hoods remove grease from cooking vapors. That grease will collect on the vents, attic rafters, insulation, and other surfaces. Grease buildup is a major fire hazard, as grease-laden surfaces can easily ignite.

The National Fire Protection Association does not recommend venting range hoods into attics for this reason. All that flammable grease accumulating in an attic is a recipe for disaster. Grease buildup also attracts pests like mice and insects.

Odors

Venting the range hood into the attic can make odors from cooking accumulate in the attic. This includes unpleasant and lingering cooking smells. The attic is not designed for proper ventilation like your home’s kitchen, so odors will tend to stick around up there.

Indoor Air Quality

Introducing cooking pollutants like grease, smoke, fumes, chemicals, and odors into your attic space can worsen your home’s indoor air quality. Many range hood filters do not capture smaller particles and gases/vapors that can be hazardous or irritating if inhaled in large amounts.

Attic Ventilation

Attics require proper ventilation separate from a range hood vent. They need soffit vents low on the eaves and gable or ridge vents high on the roof peak to create airflow through the attic. Just venting a range hood into the attic is not enough – those other vents need to be adequately sized to handle the added moisture and airflow.

Ducting Issues

Running a range hood vent ductwork through an attic space invites issues like crushed or disconnected ducts. The ductwork needs to be properly supported. Hot grease-laden air can also overheat plastic ducts. Rigid metal ductwork is recommended for range hood venting.

Proper Venting Methods

While venting a range hood into the attic is not advised, there are a few proper venting methods to use instead:

• Vent through the roof – Route the ductwork through the attic and vent it to the outdoors through the roof. Have at least a 3″ clearance from combustible materials.
• Vent through the exterior wall – Duct the range hood vent directly through the closest exterior wall. Short, straight duct runs work best.
• Vent through soffit – Carefully duct the range hood to a soffit vent, ensuring the soffit has adequate airflow capacity.

Any venting through the roof or exterior walls should have a backdraft damper installed to allow ventilation while preventing cold air from entering the home. Venting codes must be followed, and vent ducts require proper slope, sizing, and materials.

Using Makeup Air

When venting a range hood to the exterior, it can create negative pressure in the home as it pumps out indoor air. This can backdraft chimneys and pull dangerous gases like carbon monoxide into the home from furnaces, water heaters, and other combustion appliances.

To counteract this, a makeup air system can be installed along with the range hood venting. This supplies fresh replacement air from outside to balance the air expelled by the hoods fans.

Conclusion

Venting a range hood directly into the attic can cause moisture damage, grease buildup, odors, air quality issues, ventilation problems, and fire hazards. It is greatly preferable to vent range hoods directly outdoors through the roof or wall, or through a soffit vent designed for the added airflow.

Care must be taken to install proper ducting and follow all codes. Using rigid metal ductwork, adequate duct sizing, backdraft dampers, and makeup air systems can maximize ventilation while preventing issues.

While adding a new vent through the roof or wall can be more complex and costly, it is worth it to properly vent range hoods and avoid the many problems associated with improper venting into attics and other indoor spaces.

Frequently Asked Questions

Why can’t you vent a range hood into the attic?

Venting a range hood into the attic introduces excessive moisture, grease buildup, odors, and pollutants into the attic space. This can lead to mold, fire hazards, pest infestations, and indoor air quality issues. Attics are not designed for proper ventilation like a kitchen.

What are the fire hazards of venting a range hood into the attic?

Grease and other flammable particles exhausted by the range hood will accumulate on attic surfaces. Grease buildup greatly increases the risk of a fire starting and spreading rapidly. The National Fire Protection Agency warns against venting range hoods into attics.

How can venting a range hood into the attic damage the attic?

The moisture and humid air introduced into the attic can cause problems like mold growth, rotting of wood structures, insulation degradation, and damage to stored items. Grease deposits also attract pests and make attic insulation less effective.

What is the proper way to install range hood venting?

The hood should vent directly to the home’s exterior through the roof or wall. Rigid metal ductwork, proper slopes, and backdraft dampers should be used. Ventilation codes must be followed. Venting through soffits is also an option if designed for the added airflow.

How do you vent a range hood without causing problems?

Vent it directly outdoors and use makeup air if needed to balance the ventilation system. Follow codes for duct sizing, materials, and termination. Make sure other attic and home vents are adequately sized. Routinely clean the hood and ducts to reduce grease buildup.

Can you vent a range hood into a chimney?

No, it is not recommended to vent range hoods into chimneys, even unused ones. Chimneys are not designed for grease buildup and moisture like range hood ducting is. Additionally, shared ventilation can allow odors to mix between the fireplace and kitchen.

Key Takeaways

• Venting a range hood directly into an attic can cause moisture, grease, odor, pest, fire, and ventilation issues.
• Proper venting to the exterior through the roof or wall is recommended instead.
• Codes and requirements for materials, ducting, and termination must be followed.
• Attics need their own separate balanced ventilation system.
• Makeup air may be required to prevent backdrafting from increased ventilation.
• Regular cleaning of hoods and ducts reduces venting hazards like grease buildup.

Venting Recommendations By Type of Range Hood

Range Hood Type	Recommended Venting Method
Under-cabinet	Through roof or exterior wall
Chimney or wall-mounted	Through roof or soffit
Downdraft	Through floor or exterior wall
Island mount	Through roof or high wall
Built-in/insert	Through roof, wall, or soffit
Vented microwave over range	Through roof or exterior wall

The key is ducting all types of residential range hoods directly outdoors, not into attics or other interior spaces. Professional installation is recommended to ensure proper venting for the specific range hood type.

Conclusion

Venting a range hood directly into an attic is inadvisable and can lead to many problems down the road. It is important to properly vent range hoods outdoors through the roof, side walls, or soffit vents designed for the airflow. Following building codes and using rigid, sloped metal ducts with backdraft dampers will maximize ventilation while preventing issues like fire hazards, moisture damage, grease buildup, and odors.