Range hood venting is the part of a GTA kitchen renovation that gets the least attention and quietly causes the most regret. The hood itself is the easy decision — pick a width, pick a finish, decide whether it has to be a statement piece. The hard decisions are the ones nobody talks about until they bite: how many cubic feet per minute do you actually need, are you ducting it outside or recirculating it through a charcoal puck, does Ontario code force you to add a makeup air unit, and is your existing ductwork actually capable of moving the air the spec sheet promises. We spend a lot of spring kitchen jobs untangling those four questions on homes where the previous renovation answered them with a shrug. This is the guide we wish every Toronto homeowner had before they walked into a showroom.
Why range hood venting is the part of your kitchen reno that quietly fails
Almost every range hood we pull off a 1990s or 2000s GTA kitchen has the same set of problems. The duct is undersized — 4 inches when it should be 6 or 8. It is corrugated flexible aluminum when it should be smooth galvanized or stainless. It runs through the joist bay with three sharp 90-degree turns and an extra ten feet of run because the previous installer did not want to cut a new hole in the rim joist. The hood itself is rated 600 CFM on the box but is moving closer to 250 CFM through that duct. And then the homeowner upgraded to a gas range with a 60,000 BTU front burner two years ago, which is now dumping unburned combustion byproducts into the house every time the family makes Sunday dinner.
None of this is a fire-and-brimstone story. It is just slow, cumulative, and invisible until the kitchen window starts fogging up in winter, the upper cabinet finishes start hazing, and somebody develops a cough that does not quite go away. We see it constantly in spring kitchen consultations because spring is when people start opening windows again and noticing the smells from last winter’s cooking that never actually left the house.
The fix is not exotic. It is taking the four questions seriously, in order: sizing, ducting, termination, and makeup air. Get those four right and the hood you pick is almost incidental.
The CFM math: how big does your hood actually need to be?
The two rules of thumb that actually hold up in the field are the linear-foot rule and the BTU rule. Use whichever produces the larger number.
The linear-foot rule: take the width of your cooking surface in feet, multiply by 100 if you have a gas cooktop, by 50 if you have an induction or radiant electric. A 30-inch gas range is 2.5 feet wide, so 250 CFM minimum. A 36-inch gas range is 3 feet, so 300 CFM minimum. A 48-inch pro-style range with side-by-side gas and griddle is 4 feet, so 400 CFM minimum.
The BTU rule: take the total BTU output of your cooktop, divide by 100. A four-burner residential gas cooktop with a 17,000 BTU power burner and three 10,000-12,000 BTU side burners totals roughly 50,000 BTU at full tilt, which suggests 500 CFM. A pro-style 36-inch gas range with two 18,000 BTU burners and four smaller burners can hit 80,000-100,000 BTU, which suggests 800-1,000 CFM. The 48-inch dual-fuel and gas pro ranges with grills, griddles, and infrared broilers can push past 120,000 BTU, which is where the 1,200 CFM hood numbers come from.
The two rules disagree all the time, and the BTU rule is almost always the right one. Linear-foot sizing was developed for residential burners that topped out around 9,000 BTU. Modern gas ranges put out so much more heat that you cannot reasonably size a hood for them on width alone.
Two important caveats. First, CFM ratings on the box are usually measured at zero static pressure — the hood blowing into open air with no duct attached. As soon as you connect ducting, every elbow, transition, run length, and termination cap eats CFM. A 600 CFM hood with a thirty-foot duct run, two 90-degree elbows, and a backdraft damper at the wall is realistically delivering 350-450 CFM. Always size up by 25-40% to account for static pressure losses. Second, induction is genuinely different from electric coil radiant. Induction has almost no radiant heat loss, so the cooking surface itself is not heating the kitchen air the way a gas flame does. Many induction users get away with smaller hoods than the linear-foot rule would suggest, but you still need to capture cooking effluent — steam, grease aerosols, particulate from searing — and that part does not change.
Ducted vs. recirculating: when each one is honest
A ducted range hood pulls air through a grease filter, into a duct, and out of the building. A recirculating range hood pulls air through a grease filter and then through a charcoal filter, and exhausts the result back into the kitchen. Recirculating hoods are sometimes called ductless or ventless.
The honest answer about recirculating hoods is that they remove some of the smell and some of the grease but they do not remove the moisture, they do not remove the carbon monoxide from a gas burner, and they do not actually ventilate your kitchen. They are filters, not vents. They have a place — apartments where the building does not allow exterior penetrations, condos with no exterior wall on the kitchen, basement secondary suites where a long duct run is impossible. Outside of those constraints, recirculating is a compromise that gets sold as a feature.
Ducted is the right answer for any standalone GTA house with a gas range. Period. The argument we hear most often against ducted is “the duct run is too complicated and it would cost too much to do right.” The argument we have for that is that the cost of doing it right is real, but the cost of doing it wrong — moisture damage to upper cabinets, slow indoor-air-quality decline, eventual mould remediation — is real too, and it shows up later when the receipts are harder to read.
If you are stuck with recirculating because of building constraints, the realism is this: replace the charcoal filter every three to six months depending on cooking frequency, accept that you are not actually ventilating, and run the bathroom fan on the same floor while you cook to give the moisture somewhere to go. We have a parallel guide on bathroom exhaust ventilation at Ontario Bathroom Exhaust Fan Code and Upgrade Guide 2026 that covers CFM sizing and code for bathroom fans — useful background if your kitchen and bathroom share a moisture-management problem.
Makeup air: when Ontario code forces the conversation
The sentence that triggers the most callbacks on our kitchen quotes is “your hood is going to need a makeup air unit and the math just changed your project budget.” It is worth understanding why Ontario building code makes this call.
The Ontario Building Code, in Article 9.32.3.6, requires a mechanically-supplied makeup air system whenever the dwelling unit contains a fuel-burning appliance that is neither direct-vent nor uses a mechanical-draft venting system, and an exhaust system in that dwelling unit can move more than 400 CFM. In plain language: if your house has an atmospherically vented gas water heater, gas fireplace, or older gas furnace — the kind that draws combustion air from inside the house and vents through a B-vent up the chimney — and your kitchen exhaust can move more than 400 CFM, you need to mechanically supply replacement air to the house when that exhaust runs.
The reason is backdrafting. A 600, 800, or 1,200 CFM hood running in a tight modern home creates negative pressure that the makeup air has to come from somewhere. Without an intentional makeup air supply, that air comes from the easiest path of least resistance, which is often the chimney of an atmospheric appliance. Reverse flow down a B-vent pulls combustion gases — including carbon monoxide — back into the house. This is not theoretical. It is the leading cause of CO scares in newer-construction GTA homes that retrofit a high-CFM hood without considering the existing combustion appliances.
The 400 CFM threshold is not arbitrary. It is the number building code reviewers landed on as the largest exhaust draw a typical Ontario home of average air-tightness can absorb through normal envelope leakage without depressurizing enough to backdraft. Above that, you need to actively replace the air.
Three practical paths to makeup air compliance:
The cheapest is a passive backdraft damper tied to the hood circuit, drawing outdoor air through an insulated wall sleeve. Material cost $400-$900, install $500-$1,200. Works on paper, but in a Toronto winter the incoming air is below freezing and you are dumping it into your kitchen at floor level whenever the hood runs. The wife-acceptance factor is low.
The middle path is a tempered makeup air unit — an inline electric or hydronic preheater conditioning the incoming air to roughly room temperature before it enters the kitchen. Equipment $1,500-$3,000, install $1,500-$3,000 depending on duct routing and electrical or hydronic source. This is the path most Toronto homes end up on for hoods in the 600-1,200 CFM band.
The premium path is a coupled HRV/ERV system where the existing whole-home ventilation increases supply when the hood runs. This requires either an HRV that already has the capacity headroom or an upgrade. Total $4,500-$8,500. Right answer for new builds and gut renovations where the HRV is already being designed in.
The simplest way out of the makeup air requirement is to either size the hood at or below 400 CFM, or replace the atmospheric gas appliances in the house with direct-vent or sealed-combustion equivalents. We have seen kitchen renovations where the right answer was actually a high-efficiency gas water heater swap as part of the kitchen scope, because the old atmospheric water heater was the only reason the makeup air conversation existed.
Ducting matters more than the hood
This is the part of the conversation where homeowners get frustrated, because it is the part where the contractor stops talking about beautiful copper hood liners and starts talking about whether you can fit an 8-inch round metal duct through the joist bay above the kitchen ceiling.
The rules that hold up across every install we have done:
Smooth metal — galvanized steel or stainless — for the entire duct run. Flexible foil duct doubles or triples the static pressure loss per foot compared to smooth metal because the corrugations create turbulence at every ridge. A 600 CFM hood on flex duct is usually delivering 300-400 CFM at the cooktop. The cost difference between smooth metal and flex on a typical run is $80-$150 in materials and maybe an extra hour of labour. Spend the money.
Diameter sized to the hood. Six-inch round is the floor for hoods up to 400 CFM. Eight-inch round is the standard for 400-900 CFM. Ten-inch is required above 900 CFM. The hood manufacturer always specifies a minimum duct diameter — follow it, and prefer one size up if the run is long or has bends.
Run length matters. Every 90-degree elbow adds the equivalent of 5-15 feet of straight run depending on the elbow radius. Two elbows and a 15-foot run is closer to 35-45 equivalent feet of resistance. Plan the duct route before you finalize the hood model.
Termination matters. A roof termination with a backdraft damper and screen is best for performance — straight up, minimal back pressure. A wall termination is fine if you use a full-flow exterior cap, not a louvred dryer-style cap. The cheap plastic dryer caps that get installed by default on too many GTA jobs cut effective CFM by 30-50%. A good wall cap with a properly sized opening costs $80-$200; a bad one costs $20-$40. The bad one will cost you $200 worth of CFM forever.
Real GTA spring 2026 range hood install costs
The numbers below assume a competent kitchen-trade contractor working in a standard Toronto-area home, materials and labour, no HST. Spring 2026 pricing — material costs are still elevated relative to pre-2024 baselines and labour rates have continued climbing.
Replacement of an existing ducted 30-inch hood with a same-size new hood, using existing ductwork: $400-$900. The hood itself is on top of that — a competent residential 30-inch hood runs $300-$1,200 retail.
New ducted 30-inch hood install where ducting needs to be run for the first time, single-storey home with attic access: $1,200-$2,200 plus the hood. Ranch bungalow with straight-up routing through the attic is the easy version of this job.
New ducted 36-inch hood install in a two-storey home with a long horizontal run through joist bays to an exterior wall: $1,800-$3,400 plus the hood. The labour goes up because routing through finished ceilings means drywall opening and patching. If the route requires soffit construction below the ceiling, add $600-$1,500.
Pro-style 48-inch hood at 1,200 CFM with new dedicated 10-inch ducting plus passive makeup air supply: $4,800-$8,500 plus the hood and makeup air equipment. The hood alone in this category runs $2,500-$8,000 retail.
Recirculating hood install with no exterior penetration: $300-$700 plus the hood. The cheapness is the entire reason this category exists; the actual cost gets paid later in air quality.
Tempered makeup air unit retrofit, residential, 600-1,000 CFM range: $4,500-$7,500 all-in. The tempering is what makes Toronto installs different from southern US installs where untempered makeup air is acceptable for more of the year.
These numbers cluster around the high end on older Toronto core homes — Etobicoke, East York, Riverdale — because the framing is unpredictable and the ductwork rarely takes the easy path. They cluster on the low end on newer suburban builds — Vaughan, Markham, Mississauga subdivisions — where the framing is consistent and contractors have done dozens of identical kitchens in the same model.
What a competent kitchen-vent spec actually looks like
When we hand a homeowner a quote for a kitchen renovation that includes range hood work, the ventilation portion of the spec covers, at minimum: hood model and CFM rating; duct material, diameter, and total developed length including elbow equivalents; termination type and location; makeup air strategy if exhaust exceeds 400 CFM; gas appliance inventory in the home and combustion-safety status of each; and the test we plan to run after install to verify actual CFM delivery is within 15% of rated CFM. That last one is the part that almost no quotes from non-specialists include.
A useful in-the-real-world reference for what a high-end install looks like — including the gas line work, makeup air integration, and full process — is the documentation our community has on a 36-inch Wolf range upgrade in Oakville at Upgraded to a 36-inch Wolf range in our Oakville kitchen — gas line, makeup air, full process. Worth reading for the cost line items and the install sequencing.
The other thing a competent spec includes is an honest answer about what your existing combustion appliances mean for the project. If the answer is “your atmospheric water heater is the reason this hood requires makeup air,” that should be in the quote, with a path. If the answer is “we replaced the water heater with a direct-vent equivalent and the makeup air requirement disappears,” that should be in the quote with the dollar value of the avoided makeup air install. Most homeowners do not get told this trade-off exists.
Spring 2026 contractor red flags
If a contractor quotes a 36-inch pro range install with a 600+ CFM hood and there is no mention of makeup air, walk. They are either unaware of OBC 9.32.3.6 or they are hoping you will not catch it. Either is a problem.
If the quote specifies flex duct anywhere in the run, push back. Flex is acceptable only as a short last-foot connection between the hood and rigid duct, and even there it is suboptimal. Anything longer is a CFM thief.
If the quote does not list duct diameter and total developed length, ask for both before signing. The numbers determine whether the hood will actually perform, and a contractor who is not tracking them is a contractor who has never had to.
If the quote is for a recirculating hood in a standalone house with a gas range, ask why. There is sometimes a real answer — historic property with no exterior penetration permitted, two-storey loft above the kitchen with no attic — and there are sometimes lazy answers. The lazy answer is “ducted is harder,” which is not a reason.
If the quote does not include a post-install combustion-safety check on the existing gas water heater, furnace, and fireplace, get one done independently. A simple worst-case-depressurization test with a pressure pan and CO meter takes a contractor about 90 minutes and costs $250-$500. That is the cheapest insurance against the worst version of this project going wrong.
Bottom line
Range hood venting is one of the few parts of a kitchen renovation that is deeply technical, regulated, and easy to get wrong in ways that show up years later. Spring 2026 in the GTA is a good window to do this right because the trades are still pre-summer-busy, gas-range upgrades have been the dominant kitchen-spec change of the last 18 months, and Ontario has continued tightening enforcement on makeup air and combustion safety in homes that retrofit higher-CFM hoods. If you are renovating, do not let the hood be the last decision. Start with the BTU rule, work backward to ducting, decide makeup air honestly, and treat the hood model as the cosmetic decision it actually is.
Track $RENO earnings on this topic — top contributors at the homeowner-and-trades intersection are tier-up candidates. Welcome to $RENO and the leaderboard at Welcome to $RENO — Quests, Rewards, Leaderboard. Link a Solana wallet on signup and helpful answers in this thread accrue toward your tier.
LF Builders handles kitchen renovations including ventilation upgrades across the GTA — see full services at lfbuilders.ca. LF Builders supports Samm Simon’s 251 km run for cancer research.