A powerful kitchen range hood seems like the perfect solution: it extracts smoke, odours and grease before they spread through the house. But what happens if the hood is too powerful for your home? And what does it have to do with your fireplace?
In a modern, airtight home (with external wall insulation and latest-generation aluminium windows), starting a large range hood creates enormous negative pressure. The air the hood extracts cannot be replaced. This is not just ineffective - it can become dangerous.
In this guide you will learn how to correctly calculate m³/h, why you need Makeup Air, and how your range hood can make your fireplace blow smoke into the living room.
The right range hood is not "the most powerful one". It is the one that matches your space exactly. Many consumers buy units rated at 700-900 m³/h for a 12 m² kitchen - result: jet-engine noise, negative pressure and wasted kilowatts.
Take the kitchen dimensions in metres (Length × Width × Height) to find the volume in cubic metres. Multiply by 10 air changes/hour (ASHRAE standard for residential kitchens). For a kitchen 3×4×2.7 m = 32.4 m³ → 324 m³/h.
If you fry often or use an indoor grill/charcoal, increase the multiplier to 12-15. If you mainly boil or use the oven, 8-10 is enough. Oversizing creates noise and energy waste.
A range hood at high speed can reach 65-75 dB (washing machine noise). At medium speed, it drops to 50-55 dB. Tip: Buy a slightly larger unit and use the medium speed - less noise, same effectiveness.
The hood canopy must be equal to or larger than the cooking hob. Ideally it overhangs by 5-10 cm on each side. If the canopy is smaller, smoke "escapes" from the sides - whatever m³/h you specify.
This scene plays out every winter in thousands of Greek homes: you light the fireplace, turn on the range hood, and suddenly smoke starts pouring into the room instead of going up the chimney.
The range hood "sucks" air out of the house. In an airtight home, there is not enough replacement air. Strong negative pressure builds up. The only open "hole" the air can find to re-enter is the fireplace flue. Result: air flows backwards through the chimney, bringing the smoke with it!
If you use a closed stove (cassette) or pellet stove indoors, backdraft does not only bring smoke - it brings carbon monoxide (CO), an odourless, invisible and lethal gas. If you are sleeping nearby, the risk is extremely serious.
In an old house with timber windows and gaps everywhere (n50 > 6), air enters freely. But in a renovated home with thermally insulated frames (n50 < 2-3), the range hood has to suck air from somewhere - and the chimney becomes its only source.
A 500 m³/h range hood in an open-plan kitchen: in 6 seconds it sucks up the air volume of a typical 3×4 m room. Without a source of fresh air, pressure drops below atmospheric, and the open-flame appliance (fireplace, gas stove) reverses immediately.
The solution is not to buy a smaller hood. The solution is to ensure an equal intake of fresh air (Makeup Air) for every cubic metre of air that goes out.
Open a window near the range hood (or in the adjacent room) while cooking. Practical but not automatic: in winter cold air rushes in, and you will not always remember.
A small opening in the external wall (Ø150-200 mm) with a louvre or metal mesh. The airflow created by the hood automatically draws fresh air through this opening. Cost: €20-50. Downside: permanently open hole (noise, cold, draught).
The ideal solution: a damper on the wall opening that opens only when the hood runs (due to negative pressure). When it stops, it closes by itself. Optional extra: an electric servo motor interlocked with the hood.
The free area of the intake opening must be equal to or greater than the exhaust outlet. For a 400 m³/h hood, you need at least a Ø150 mm open outlet. If the intake free area is insufficient, performance drops dramatically.
In a combined kitchen-living-dining room (open plan), many people calculate m³/h based on the entire open space (kitchen + living room + dining = 100+ m³). This leads them to machines rated at 700-1000 m³/h - overpowered, noisy and energy-hungry.
In open plan, calculate only the cooking zone volume, i.e. the space directly above and around the hob. This volume rarely exceeds 25-35 m³. Multiply by ×10-12 and you get 250-420 m³/h - not 1000!
A kitchen island with no overhead cabinets is the most challenging type for extraction. Smoke can escape from every side. You need a canopy 20-30 cm larger than the hob, or alternatively downdraft extraction (which pulls smoke downward).
If you cannot run an exhaust duct (e.g. high floor of an apartment block without a light well), there are recirculation hoods: the air is filtered (activated carbon) and returned to the room. Effectiveness: only 50-60% compared to ducted extraction.
Every cubic metre of air that exits in winter takes warmth with it. A 400 m³/h hood running for 1 hour "throws away" warm air worth 0.3-0.5 kWh. Correct sizing and makeup air reduce losses to a minimum.
🍳 A bigger range hood ≠ a better range hood. The right hood matches the kitchen volume, ensures makeup air intake, and does not "choke" your fireplace or stove.
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