Cooling a kitchen

Every other room on this site is cooled against the outdoor climate. A kitchen is different: it contains appliances that convert energy into heat and steam by design, for an hour or two at a time, at exactly the moment somebody is standing in front of them.

That changes the correct answer. The first move is not cooling.

Cooking puts three things into a kitchen: heat, moisture, and grease and combustion products.

A range hood ducted outdoors captures all three in the rising plume, before they disperse into the room. An air conditioner deals with two of them — expensively — after they have already mixed with the room air, and does nothing at all about the third.

The moisture point is the one people underestimate. Boiling water puts a substantial latent load into the air, and removing moisture is the part of an air conditioner’s job that costs the most energy. Venting it outside as steam is close to free by comparison.

So the sequence is: capture at the source, then ventilate, then cool the residual. Reversing it means paying to remove heat you are still making.

Range hoods are certified under the same ENERGY STAR ventilating fan program as bathroom and in-line fans, tested at 0.25 inches of water gauge. We hold data for 86 US-market certified hoods.

The caveat we are not going to skip past: eight of the 86 certified range hoods are filed at 0.0 sones. A fan moving 200 CFM produces sound, and a value of exactly zero is not a measurement of anything.

We include the Best hood because its airflow and efficacy figures are useful and there is no reason to doubt them. We would not buy it on the acoustic figure, and neither should you — go and listen to one.

For comparison, the same dataset contains bathroom fans filed at 0.1 sones, which is a small but non-zero and plausible value. More on how sones work.

• Switch it on before you start cooking, not when the pan starts smoking. A hood captures a rising plume; it cannot recover heat that has already dispersed into the room.
• Leave it running afterward. Residual heat and moisture keep rising from hot cookware and a hot hob for a good while after the burners are off.
• Use the back burners where you can. They sit further under the capture area on most hoods.
• Clean the grease filters. A loaded filter is the kitchen equivalent of a blocked air conditioner filter — airflow falls and capture falls with it. Most are dishwasher-safe.
• Give it make-up air. Pulling air out of a closed kitchen creates negative pressure that the fan then fights, so it moves far less than its rating. Crack a window on the other side of the room.

Airflow on the cook, not on the hob. A fan aimed at the stove disrupts the rising plume the hood is trying to capture, and across a gas flame it is worse than that. Place it behind or beside the person, blowing across them.

Shift the timing. The oven is the largest single heat source in most kitchens, and it runs longest. Batch-cooking in the morning, or using a countertop appliance instead of a full oven, does more for a hot kitchen than any fan.

Then, and only then, cooling. If the kitchen is still too warm when nobody is cooking, that is an ordinary room-cooling problem — size a unit from the room rather than from the cooking load, which is intermittent.