Kitchen HVAC — Condensation Diagnosis & Fix

Measure the problem, then model exhaust / make-up air to bring the dew point below the cold surface.

1 · Measured at the problem spot

Current Dew Point
Humidity ratio: Wet-bulb:

2 · Air balance

MUA as % of exhaust
Transfer/infiltration draw: Net:
About the 80–90% target

Commercial kitchens must run net-negative so heat, grease and odours don't migrate into dining/front-of-house. Best practice is MUA at ~80–90% of exhaust, with the remaining 10–20% drawn as tempered transfer air from adjacent conditioned spaces. MUA at 100%+ pushes the kitchen positive (code fail); too little MUA over-extracts, causing door-pull, hood spillage and pulling unconditioned humid air through every gap.

3 · Moisture balance & predicted fix

Predicted dew point after this ventilation
Predicted kitchen W: Ventilation rate:
How the prediction works & estimating the load

Steady-state moisture balance: incoming air enters at its humidity ratio W_in; cooking/steam adds the latent load G; the exhaust carries the mixed kitchen air out. At equilibrium the kitchen settles at W_kitchen = W_in + G ÷ (1.2 × Q), where Q is the governing extract in CMH and 1.2 kg/m³ is air density. That W is converted back to a dew point at the incoming-air temperature. Raising exhaust (bigger Q), drying/cooling the incoming air (lower W_in), or cutting the load all push the predicted dew point down.

Rough latent loads: light prep kitchen ~4–8 kg/h; busy hotel à-la-carte ~10–20 kg/h; heavy steam/wok/dishwash zones 20 kg/h+. Tune until the verdict matches what you observe, then you have a calibrated model to size the fix.