Why Your Commercial Kitchen Is Too Hot (And Why It Is Usually Not the AC)

One of the most common calls in commercial kitchens is some version of "the air conditioning is not keeping up." The kitchen is uncomfortable, the line is miserable, and the obvious conclusion is that the cooling equipment is undersized or failing. Often it is neither. The kitchen is hot because the building is losing far more air than it is getting back, and no amount of additional cooling will fix an air balance problem.

What the exhaust hood is actually doing

A commercial exhaust hood is not a fan that removes smoke from above the range. It is a system that continuously removes a very large volume of air from the building — heat, grease-laden vapour, smoke, and combustion products. That air has to come from somewhere. Every cubic foot the hood removes is a cubic foot the building has to replace.

What make-up air is supposed to do

A make-up air unit exists to replace the air the hood removes, usually tempered so it is not dumping outside air straight onto the line. When the make-up air unit is working and balanced against the hood, the kitchen stays at roughly neutral pressure and the cooling system only has to handle the actual heat load.

When make-up air is failing, undersized, switched off, or out of balance, the building goes into negative pressure. It still has to replace that air, so it pulls it in through whatever gaps it can find — door frames, gaps around windows, the dining room, and sometimes back down other vents.

Signs the problem is air balance, not cooling

• Exterior doors are hard to pull open, or they slam shut on their own.
• You can feel air rushing in around a door frame when it is opened.
• The hood no longer captures smoke properly and it rolls out into the kitchen.
• The dining room is comfortable but the kitchen is not, even though both are on cooling.
• The problem is noticeably worse when the hood is on full and better when it is off.
• Pilot lights or gas appliances behave inconsistently.

Why adding more air conditioning does not fix it

If the building is in negative pressure, unconditioned outside air is being pulled in continuously through every gap in the structure. Adding cooling capacity means you are now paying to cool a larger volume of outside air that keeps arriving. The kitchen may improve slightly, the energy cost rises, and the underlying problem — the hood and make-up air being out of balance — is untouched. The hood also still will not capture properly, which is a safety and comfort issue rather than just a temperature one.

What actually gets checked

• Whether the make-up air unit is running at all, and whether it is interlocked to start with the hood.
• Whether the make-up air volume is matched to what the hood is exhausting.
• Whether filters in the make-up air unit are loaded and choking airflow.
• Whether the hood filters are clean, since loaded filters change the whole system behaviour.
• Whether dampers and belts are in working order.
• Whether the cooling equipment itself is also underperforming, which can happen alongside an air balance problem.

Why this is worth diagnosing properly

A hot kitchen is a staffing problem as much as an equipment problem. It also tends to arrive together with a hood that is no longer capturing smoke and grease the way it should. Because the hood, the make-up air unit, and the cooling system are one interacting system, they are worth looking at together rather than one at a time.

If your kitchen is not holding temperature and you are not sure whether it is a cooling problem or an air balance problem, book a service call and have the whole system checked.