Range Hood Makeup Air Rules in Massachusetts

If your Massachusetts kitchen hood pulls more than 400 cubic feet per minute, the state's mechanical code requires the house to supply roughly that much makeup air back, and the cheapest way to comply in a typical MA home is almost always to size the hood at 395 CFM or fix the appliance side first, not to add a $2,000 to $5,000 makeup-air unit. The rule comes from 780 CMR 51.00, Massachusetts's residential building code, which adopts IRC Section M1503.6 with the 400 CFM trigger intact. The reason it bites here, and bites harder than it used to, is that a decade of Mass Save air sealing has made the housing stock tight enough for an oversized hood to backdraft an old gas water heater straight into the basement.

This guide walks through what 780 CMR actually says, which appliances in your house make the risk real, and the three ways out. We'll be honest about cost: makeup-air units are quoted in a wide band in Massachusetts and the published numbers online are not local primary data, so we'll point you to the questions to ask your contractor instead of inventing a price. For the broader permit picture, see our Massachusetts kitchen and bath permits walkthrough; this guide focuses on the hood-and-makeup-air decision specifically.

Does Massachusetts require makeup air for a range hood?

Yes, when the hood exhausts more than 400 CFM. Massachusetts's residential building code (780 CMR 51.00) adopts the IRC, currently the 10th Edition Residential, and Section M1503.6 of that code reads, in substance: exhaust hood systems capable of exhausting in excess of 400 CFM shall be provided with makeup air at a rate approximately equal to the exhaust air rate. The dampers in that makeup-air path have to be automatic and gravity-balanced or motor-actuated, and the air has to be supplied by an outdoor source.

Two things to notice in that sentence. First, the trigger is the hood's exhaust capacity, not how hard you run it. A 600 CFM hood throttled down to "low" still has 600 CFM of capability, and the inspector treats it as a 600 CFM hood. Second, "approximately equal" is a real word in code: matched supply, not a token vent. That's why a real makeup-air system is engineered ductwork with a damper and often a heater, not a hole in the wall.

The 400 CFM threshold, exactly as 780 CMR adopts it

The number is 400 CFM, full stop, and it applies to residential range hoods served by the IRC mechanical chapter. The IRC threshold has held at 400 CFM through the code cycles Massachusetts has adopted, and the state's amendments to 780 CMR 51.00 leave that figure in place. Town inspectors in Boston, Cambridge, Worcester, Springfield, and the smaller building departments all apply the same number.

Hood exhaust capacity	Makeup air required by 780 CMR / IRC M1503.6?
200 CFM	No
395 CFM	No
400 CFM	No (the rule says "in excess of 400 CFM")
401 CFM	Yes
600 CFM	Yes
900 CFM (pro-style)	Yes
1200 CFM (commercial-style)	Yes

The practical implication for most Massachusetts kitchens: a hood rated at 395 CFM, common on Broan, Best, Zephyr, and Bosch undercabinet and chimney-style models, sits one cubic foot under the line and triggers nothing. Plenty of pro-style ranges, including Wolf 30-inch and 36-inch dual-fuel, pair well with hoods in the 300 to 600 CFM range. You give up some peak smoke clearance over a hard sear, you save the makeup-air install. For most homes, that trade is worth it.

Which appliances actually trigger the backdraft risk

The 400 CFM rule exists because a large hood can pull more air out of a house than the rest of the building can replace through normal leakage, and the easiest path for replacement air to come back in is sometimes down the flue of a combustion appliance. That reverses the flue and pushes exhaust, including carbon monoxide, into the living space. The rule applies regardless of what's in the basement, but the safety stakes depend entirely on which appliances you have.

Appliance	Vents how?	Backdraft risk if hood is oversized?
Atmospheric gas water heater (old-style, draft hood, B-vent)	Natural draft up a flue	High
Atmospheric gas or oil boiler / furnace	Natural draft up a flue	High
Open masonry fireplace	Natural draft up a chimney	High
Wood stove with a draft control	Natural draft, but actively burning	Moderate
Sealed-combustion (direct-vent) gas water heater	Pulls combustion air from outside through a concentric vent	Very low
Sealed-combustion / 90%+ AFUE condensing furnace or boiler	Outside combustion air, plastic vent	Very low
Heat-pump water heater	Electric, no combustion	None
Electric water heater	Electric, no combustion	None
Cold-climate heat pump (heating)	Electric, no combustion	None
Induction or electric range (the cooktop itself)	n/a, the hood is the issue	n/a

If everything in your mechanical room is sealed combustion or electric, the makeup-air conversation is about comfort and code compliance over 400 CFM, not life safety. If you still have an atmospheric gas water heater in the basement (very common in pre-1990 Boston triple-deckers, Cambridge two-families, Somerville singles, and Worcester three-deckers), the backdraft risk is real and the cheapest fix is often to swap the water heater, not to add a makeup-air unit. More on that in a moment.

Why this is a Massachusetts problem now

Two MA-specific things turned a national code rule into a local headache: Mass Save weatherization made houses much tighter, and the housing stock still has a lot of atmospheric appliances sitting in those tighter basements. Twenty years ago a 600 CFM hood in a leaky 1920s colonial pulled makeup air through the rim joist and the window sashes, nobody noticed. The same hood in the same house after Mass Save air sealing, dense-packed cellulose, and new triple-pane windows pulls it down the water-heater flue.

Our Massachusetts home air sealing guide covers the weatherization side of this, including the combustion-safety test (CAZ test) that a real Mass Save assessor runs before and after sealing. If your house has been through that program in the last decade, you have already crossed into "tight enough that a big hood matters" territory. That's the context inspectors are quietly applying when they ask about makeup air on a kitchen permit.

The three ways out

You have three options when designing a Massachusetts kitchen with a serious cooktop. Pick deliberately, because they have very different costs.

Option 1: size the hood at 395 CFM or below. Cheapest, fastest, no makeup-air equipment, no extra inspection. Trade-off: peak smoke clearance is lower, which matters most over a 36-inch or 48-inch pro range with a high-BTU griddle. For a 30-inch gas range or any induction cooktop, 395 CFM is usually plenty. Many Bosch, Zephyr, and Broan models offer 395 CFM SKUs precisely because of this rule.

Option 2: fix the appliance side first. If the only atmospheric appliance left in the basement is the water heater, swap it for a sealed-combustion direct-vent gas unit, a heat-pump water heater, or a tank-style electric. A heat-pump water heater carries a Mass Save rebate that can take a meaningful bite out of the equipment cost. Once the last natural-draft flue is gone, the life-safety reason behind the makeup-air rule mostly goes with it, and the inspector's conversation is about comfort and code over 400 CFM rather than carbon monoxide. You still need to comply with M1503.6 if the hood exceeds 400 CFM, but the failure mode if something goes wrong is far less dangerous.

Option 3: install a real makeup-air unit (MUA). A whole-house MUA is engineered ducted supply air with an automatic damper interlocked to the hood, almost always with a heater so January air doesn't blast onto the cooktop at 5 degrees. It's the right answer if you genuinely want a 900 or 1200 CFM hood over a Wolf 48 or a BlueStar Platinum. It is not the right answer for someone who picked a 600 CFM hood because the salesperson upsold it.

What does a makeup-air unit actually cost in Massachusetts?

Honest answer: ranges quoted online are wide and most of them are not Massachusetts data, so the only number worth giving you is "ask two MA HVAC contractors and a kitchen-bath GC for itemized quotes." A heated, ducted MUA system involves new exterior penetrations, balanced ductwork, a heater (electric or hydronic), a damper, the controls that interlock it with the hood, and a permitted gas or electrical tie-in. None of that is cheap in a finished house.

For context inside a kitchen budget overall, see our Massachusetts kitchen and bath remodel cost guide and the breakdown of why kitchen quotes vary so much. An MUA line on a kitchen quote is one of those items that's invisible if the contractor assumed a 395 CFM hood and very visible if they assumed a 1200 CFM commercial-style. Make sure the assumption is written down.

A practical rule for budgeting: if your contractor is pricing a hood over 400 CFM and there's no MUA line in the quote, ask why. Either they're planning to fail the inspection, they know about a sealed-combustion mechanical room you forgot to mention, or they're going to bill the MUA later as a change order.

Permits, inspections, and who actually pulls them

Range-hood makeup-air work in Massachusetts is mechanical-permit territory, with gas, electrical, and sometimes building permits stacked alongside depending on what changes. The licensed HVAC contractor or sheet-metal contractor pulls the mechanical permit for the MUA. The plumber/gasfitter pulls the gas permit if a gas appliance is being swapped. The electrician pulls the electrical permit for any new circuit feeding the MUA heater or interlock. The general contractor coordinates all of it.

Inspectors look for three things on the rough inspection: the makeup-air ductwork is sized for the hood it serves, the damper is automatic (not a manual slider the homeowner can leave closed), and the supply is interlocked with the hood so it opens when the hood runs. They also check that the supply is from outside, not from a vented attic or an attached garage.

What about induction or electric ranges?

If your cooktop is induction or electric, you still have to follow the 400 CFM rule for the hood itself, because M1503.6 is about exhaust capacity, not what's being cooked. The realistic answer is that almost nobody needs more than 400 CFM over induction; the cooktop produces no combustion products, no flame, and no grease aerosol you can't catch with a 300 to 395 CFM hood properly mounted at the right height. The pro-style 1200 CFM hood over an induction range is almost always a mismatch sold on aesthetics.

This also means: if you're converting from a gas range to induction (a common Mass Save adjacent move, often with a panel upgrade), you can usually drop your hood size at the same time, eliminate the makeup-air requirement, and stop running a flame in the house. It's one of the cleaner decisions in a 2026 MA kitchen remodel.

A note on rebates and tax credits

The state rebates that touch this decision are mostly on the appliance side, not the hood side. Mass Save offers rebates on heat-pump water heaters and on certain induction-range pilots that have rotated through Eversource and National Grid territories. Those rebates can shift the math toward Option 2 (fix the appliance side) by lowering the cost of a sealed-combustion or electric replacement.

What does not apply: the federal 25C Energy Efficient Home Improvement Credit, which used to cover certain envelope and equipment work, expired December 31, 2025, and does not apply to 2026 work. Don't let an old blog post or a salesperson tell you it does.

FAQ

Does Massachusetts require makeup air for a range hood? Yes, when the hood exhausts more than 400 CFM. The state residential code 780 CMR 51.00 adopts IRC Section M1503.6, which requires makeup air at approximately the exhaust rate for any hood capable of more than 400 CFM. At or below 400 CFM, no makeup air is required by code.

Do I need makeup air if I have an induction range? Only if the hood itself is rated over 400 CFM. The rule is about the hood's exhaust capacity, not the cooktop. The good news is induction rarely needs more than 300 to 395 CFM, so most induction-range kitchens land under the threshold by design.

Do I need makeup air if my furnace and water heater are sealed combustion? You still need to comply with M1503.6 if the hood exceeds 400 CFM, but the life-safety reason behind the rule, backdrafting an atmospheric flue, doesn't apply when all combustion appliances pull air from outside. The inspector still applies the code; the actual carbon-monoxide risk is much lower.

Can I install a smaller hood to avoid the makeup-air requirement? Yes, and it's often the smart move in a Massachusetts kitchen. A 395 CFM hood sits one cubic foot under the threshold, triggers no makeup-air requirement, and is enough for most 30-inch gas and induction cooktops. For a 48-inch pro range with a high-BTU griddle, you'll likely want more, and then the MUA is honest engineering, not a tax.

Does the rule apply to a remodel or only new construction? A remodel that installs a new hood with a capacity over 400 CFM has to comply, because the new equipment triggers the mechanical permit and the inspection. An existing oversized hood that predates your purchase of the house is not retroactively required to add MUA, though it's worth thinking about anyway if the basement still has an atmospheric flue.

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Ready to size the hood and decide between "395 CFM" and "real MUA"? Get matched with Massachusetts kitchen-bath contractors who'll quote both options against your specific mechanical room at /get-estimate. For the broader project picture, browse Massachusetts kitchen and bath remodelers.