Kitchen humidity: the second-largest moisture source in the house
Only the bathroom produces more moisture. The difference is that most kitchens have a range hood that removes nothing.
- Target humidity
- Under 60%
During and shortly after cooking
Cooking is the second-largest moisture producer in most homes after bathing, and unlike a shower it happens several times a day. A pot simmering with the lid off releases a remarkable amount of water — enough that a single evening's cooking can move a whole-house humidity reading.
The problem specific to kitchens is that most people believe they already have extraction, when what they have is a filter.
The recirculating hood problem
A range hood comes in two kinds. A ducted hood moves air out of the building. A recirculating one pulls air through a grease filter and a charcoal cartridge and blows it straight back into the kitchen. It removes grease and some odor. It removes precisely zero moisture.
The difference is invisible from the front, and a large share of kitchens — particularly in apartments and island installations — have the recirculating kind. If you cannot trace a duct leaving the building, it is not extracting moisture.
The other kitchen-specific issue is that moisture spreads. Kitchens usually open onto living space, so the water vapor from cooking migrates into rooms with colder surfaces and condenses there instead.
Where the moisture comes from
- Boiling and simmering without lids — the largest single contributor
- A recirculating range hood that returns all steam to the room
- A dishwasher venting steam at the end of its cycle
- Washing up in a hot sink, and leaving dishes to air-dry
- A washing machine or dryer in the kitchen with no external venting
The plan for this room
Ranked by what it costs you. Work down the list — most rooms are fixed before the paid options.
Put lids on pans. It cuts moisture release dramatically and shortens cooking times.
Turn the hood on before you start and leave it running 10–15 minutes after you finish.
Shut the kitchen door while cooking so the moisture does not migrate into cooler rooms.
Trace your hood ducting. If it does not leave the building, you have no moisture extraction and you should plan around that.
Open a window while cooking in cool weather — a kitchen is the one place where a quick cross-draft is nearly always worth it.
Convert a recirculating hood to ducted if the wall or roof run is feasible. It is the single biggest improvement available in a kitchen.
If ducting is impossible, fit a separate extractor fan in an external wall, sized to the room.
Move the dryer out of the kitchen, or vent it externally. An unvented dryer in a kitchen is two large moisture sources in one room.
What will not work here
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A recirculating hood
Grease filter with a fan. It cannot remove water vapor, whatever the marketing says about odor.
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Leaving the oven door open after cooking "to use the heat"
It releases the moisture from whatever was in it directly into the room, and it is not an efficient way to heat anything.
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A dehumidifier in the kitchen
It cannot keep up with a boiling pot in real time. Extraction at the source is an order of magnitude more effective.
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Air fresheners for the cooking smell
The smell is the least of it. The moisture is the part that ends up condensing in another room.
Through the year
Winter
Peak risk — the moisture has cold surfaces to find. Hood on, lids on, kitchen door shut.
Summer
Less condensation risk indoors, but the load on your AC is real. Extraction still pays.
Common questions
Does cooking cause condensation?
Yes — it is the second-largest moisture source in most homes after bathing. Boiling and simmering without lids releases several pints across a day of normal cooking.
Do recirculating range hoods remove moisture?
No. They filter grease and some odor and return the air, steam included, to the kitchen. Only a ducted hood that terminates outside removes moisture.
Should I open the kitchen window while cooking?
In cool weather, yes — it is one of the most reliably useful times to ventilate. On a humid summer day, use the hood instead.
How long should I run the range hood after cooking?
10–15 minutes. Surfaces and the food itself keep releasing moisture after the burners go off.