How Is Make-Up Air Designed for Commercial Kitchens?

Commercial kitchen make-up air design provides replacement air for kitchen exhaust hoods per the mechanical code: sizing make-up air units for the total exhaust volume, tempering the air for comfort and code, distributing it without disrupting hood capture, and balancing the kitchen slightly negative to the dining areas. The design coordinates with the hood exhaust and the building HVAC as one air-balance system. The air balance is the whole game. Too little make-up air and the kitchen starves; too much and cooking odors push into the dining room. The engineer calculates the balance explicitly — exhaust totals, make-up totals, transfer air from the dining area, and the resulting pressure relationship — and documents it. The health department and the building department both look at kitchen ventilation, so the design answers both.

Sizing starts with the hood schedule: each hood's exhaust rate per its listing and the cooking equipment beneath it. The make-up air total follows, typically replacing the large majority of the exhaust, with the small remainder made up by transfer air from adjacent spaces — which is what keeps the kitchen negative to dining. The unit gets selected for the airflow, the tempering load, and the filtration the application needs. Distribution is where good designs separate from bad. Make-up air dumped at high velocity near the hoods destroys their capture efficiency — the air curtain pushes effluent right past the filters. I distribute make-up air low and slow, away from the hoods: perforated diffusers, displacement-style delivery, or dedicated make-up plenums at the back of the cook line. The goal is replacing air without creating the cross-drafts that defeat the exhaust system.

Conditioning thousands of cubic feet of outside air per minute is expensive, which is why the energy code cares about kitchen ventilation and why I design the controls thoughtfully. Demand-controlled kitchen ventilation — sensors that ramp hood exhaust and make-up air with actual cooking activity — cuts the energy penalty dramatically during idle periods. Heat recovery from the exhaust stream can preheat make-up air where the application allows. In California, the kitchen ventilation design documents to the 2025 California Energy Code (2025 Standards), effective January 1, 2026, including its kitchen exhaust and demand-control provisions. The permit package shows the hood exhaust design, the make-up air sizing and distribution, the air-balance calculations, the control sequences, and the energy compliance — the complete kitchen air system, engineered as one.

• Air balance: make-up air sized to exhaust, kitchen held slightly negative to dining
• Tempering: heated/cooled make-up air for comfort, code, and energy compliance
• Distribution: low-velocity delivery away from hoods to protect capture efficiency
• Demand control: sensor-based modulation cutting energy during idle cooking periods
• Coordination: hood exhaust, make-up air, and building HVAC as one balanced system