Key takeaways
- Passive damper: Opens from pressure difference. It is inexpensive but airflow changes with wind, house pressure, and hood speed.
- Motorized damper: Opens when the hood or a dedicated control calls for makeup air. This is usually the most predictable residential choice.
- Fan-assisted system: Uses a blower to deliver a controlled amount of air. It is preferable when the duct run is long, the house is tight, or the required airflow is substantial.
- Tempered-air system: Heats or otherwise conditions incoming air before it enters the living space. It costs more but can prevent uncomfortable cold-air dumping in winter.
The best makeup air damper for a kitchen is one sized to deliver the range hood’s actual exhaust rate, with a motorized control, a properly sealed exterior hood, and a rating that matches your climate and local mechanical code.
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Best makeup air damper by kitchen situation
| Kitchen situation | Best choice | Typical target | Why it fits |
|---|---|---|---|
| Occasional cooking, hood below 400 CFM | Passive or pressure-assisted wall damper | 4–6 inch duct; up to about 200 CFM | Lower cost and simpler installation, provided the home does not need controlled tempered air |
| Typical residential hood, 400–800 CFM | Motorized six- or eight-inch makeup-air damper | 200–400 CFM of makeup air | Good balance of controllability, weather sealing, and installation space |
| High-output hood, 800–1,200 CFM | Motorized eight- or ten-inch damper, often with an interlocked fan | 400–600 CFM or more | Reduces excessive negative pressure and is easier to coordinate with code-required ventilation |
| Cold or very hot climate | Motorized damper with tempered-air or dedicated HVAC integration | Matched to calculated exhaust airflow | Unconditioned outdoor air can cause drafts, condensation, freezing, or unnecessary heating and cooling loads |
How much makeup air does a range hood need?
Start with the hood’s rated CFM, but do not assume that rating equals the amount of replacement air required in every jurisdiction. Some codes and standards trigger makeup-air provisions when a dwelling’s exhaust appliance exceeds a specified airflow, commonly around 400 CFM. The exact threshold and required control method vary by location, appliance type, building tightness, and adopted code edition.
As a practical sizing exercise, a 900-CFM hood does not necessarily require a 900-CFM outdoor-air damper. Existing house leakage, other exhaust fans, and the hood’s real operating speed affect the result. A designer may specify 300 to 600 CFM of controlled makeup air, or a system that supplies air equal to the hood’s exhaust under certain operating conditions. Have the final airflow and interlock reviewed by the HVAC contractor or local building department.
Worked sizing example
Suppose a hood is rated at 600 CFM and the design calls for makeup air equal to 60% of hood exhaust:
600 CFM × 0.60 = 360 CFM of makeup air.
A nominal six-inch round duct has an area of about 0.196 square feet. At 360 CFM, the average air velocity would be roughly 1,840 feet per minute, which can be noisy and restrictive. An eight-inch duct has about 0.349 square feet of area, reducing velocity to approximately 1,030 feet per minute. The eight-inch option may therefore be quieter and less resistant, even if a six-inch damper appears to meet the airflow number on paper.
Actual delivered airflow depends on duct length, elbows, screens, grilles, damper pressure drop, and the fan used to move the air. Ask for a fan curve or pressure-drop data rather than choosing by nominal diameter alone.
What to look for in the best makeup air damper for kitchen use
1. A confirmed airflow rating
Look for a published CFM range at a stated static pressure, such as 0.2 or 0.4 inches water column. A claim such as “eight-inch damper” tells you the connection size, not how much air the assembly will deliver. For a high-output hood, prioritize a complete system rating that includes the outdoor grille, filter, duct, damper, and supply fan.
2. Correct damper type
- Passive damper: Opens from pressure difference. It is inexpensive but airflow changes with wind, house pressure, and hood speed.
- Motorized damper: Opens when the hood or a dedicated control calls for makeup air. This is usually the most predictable residential choice.
- Fan-assisted system: Uses a blower to deliver a controlled amount of air. It is preferable when the duct run is long, the house is tight, or the required airflow is substantial.
- Tempered-air system: Heats or otherwise conditions incoming air before it enters the living space. It costs more but can prevent uncomfortable cold-air dumping in winter.
3. Weather sealing and drainage
The outdoor termination should include a hood or louver that resists wind-driven rain, insects, and snow. A backdraft flap or motorized blade should close tightly when the system is off. Look for a corrosion-resistant exterior, such as aluminum or stainless steel, and a design that sheds water rather than directing it into the duct.
Common failure points include a warped plastic flap, a clogged insect screen, deteriorated gasket material, and an exterior hood installed too close to an obstruction. A damper that leaks when closed can create winter drafts and allow moisture into the wall assembly.
4. Control and interlock compatibility
The damper should open before, or at the same time as, the range hood starts. Many installations use a 120-volt motorized damper controlled by a relay, while others use low-voltage controls or a dedicated makeup-air controller. Confirm whether the damper is normally open or normally closed, what voltage it requires, and whether the hood provides a compatible dry-contact signal.
Do not connect a motorized damper directly to a hood circuit unless the manufacturer’s wiring instructions permit it. A relay or control module may be needed. The system should also fail in a manner accepted by the installation instructions and local code; a damper that never opens could leave the house under excessive negative pressure.
Installation details that affect performance
- Choose the intake location. Place the outdoor opening away from dryer exhaust, plumbing vents, vehicle exhaust, combustion vents, and areas where snow accumulates. Follow local separation distances.
- Keep the duct short and smooth. Use the manufacturer’s approved duct size. Avoid unnecessary elbows and abrupt reductions because they increase pressure drop and noise.
- Install the damper in an accessible position. It will eventually need inspection, cleaning, or replacement. Do not bury the motor behind permanent framing.
- Seal every joint. Use approved foil HVAC tape or mastic on duct seams. Seal the wall penetration with appropriate exterior-grade flashing and sealant, not household tape.
- Insulate cold-air ductwork. Insulation helps prevent condensation on the duct and reduces the chance of cold surfaces damaging nearby materials.
- Provide a suitable indoor discharge point. Supply air should not blow directly across a cooktop, onto occupants, or into a confined cavity. A diffuser or connection to the return-air system may be required.
- Test the interlock. Turn on each hood speed and verify that the damper opens, the fan operates if provided, and the flap closes after the hood is switched off.
Code, combustion, and HVAC considerations
Makeup air is not only a comfort feature. A powerful hood can depressurize a tight home, interfere with naturally drafted water heaters or furnaces, pull flue gases into the building, and increase door-closing forces. If the home has gas, oil, or wood-burning appliances, ask a qualified HVAC professional to evaluate combustion air and pressure relationships.
Local requirements may specify a maximum hood airflow, a dedicated makeup-air system, automatic activation, tempered supply air, testing, or a particular control sequence. The hood manufacturer’s installation manual may also impose minimum duct sizes and maximum equivalent duct lengths. Obtain permits where required and avoid treating a small wall grille as a substitute for a code-compliant system.
Ownership realities: what needs maintenance?
- Exterior grille: Inspect seasonally for leaves, lint, insects, ice, and snow. Blockage can sharply reduce airflow.
- Filter: If the system has an intake filter, clean or replace it according to the pressure-drop indicator or service schedule. A dirty filter makes the hood system louder and less effective.
- Damper blade and hinge: Dust and grease can make the blade stick, especially if the intake is connected near kitchen air rather than directly outdoors.
- Motor and actuator: Listen for clicking, buzzing, or repeated cycling. These symptoms can indicate a worn gear, failed end switch, or incorrect control voltage.
- Seals and insulation: Check for daylight, drafts, water staining, or condensation around the wall penetration. Replace damaged gaskets and renew exterior sealant when necessary.
A frequent mistake is selecting a damper by duct diameter while ignoring pressure drop. Another is installing an oversized passive opening that creates a cold draft whenever the hood runs. A third is placing the intake where it can draw in dryer exhaust or combustion products. These problems are harder to correct after drywall and siding are finished, so confirm the layout before installation.
Bottom line
For most kitchens with a 400–800 CFM hood, the best makeup air damper for kitchen ventilation is a motorized six- or eight-inch unit with a published airflow rating, tight closed-position sealing, a weather-resistant exterior termination, and a control interlocked with the hood. Choose a fan-assisted or tempered-air system for larger hoods, long duct runs, very tight homes, or cold climates. Match the complete system to measured airflow and local code, then have the wiring, combustion safety, and final pressure performance checked by qualified professionals.
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