Make-up air — the conditioned outdoor air supplied to replace kitchen exhaust — is perhaps the least appreciated aspect of kitchen ventilation design. Poor make-up air design undermines even the best ESP system, causing capture failure, drafts, temperature discomfort, and energy waste. This guide covers the principles of good make-up air design for ESP-equipped kitchens.
| Parameter | Specification |
|---|---|
| Air Balance Target | Kitchen slightly negative to adjacent spaces (-0.02 to -0.05 in. w.c. / -5 to -12 Pa); prevents odor migration while allowing door operation |
| Make-Up Air Volume | 80-90% of exhaust volume (the remaining 10-20% is transfer air from adjacent spaces) |
| Supply Air Temperature | Heated to 10-15°C in winter (tempered, not fully heated); Cooled to 27-29°C in summer (not fully cooled) — energy-efficient tempering strategy |
| Supply Air Distribution | Low-velocity displacement from perimeter; NOT directed at hoods (disrupts capture) |
| Energy Recovery | Run-around coil or heat pipe recovering 50-60% of exhaust heat for supply air pre-conditioning |
Application Scenarios
- Restaurant comfort problem diagnosis: A restaurant with excellent ESP performance was receiving staff complaints about kitchen temperature (35°C+ at cooking line). Investigation found: make-up air was being supplied at outdoor temperature (34°C in summer), directed at the cooking line at high velocity, and the kitchen was excessively negative (-30 Pa) — causing hot outdoor air to be pulled in through every opening. The fix: rebalanced make-up air to 85% of exhaust, tempered supply air to 28°C, redirected diffusers away from hoods. Kitchen temperature dropped to a comfortable 28°C. Staff turnover decreased.
- Energy recovery implementation (cold climate): A restaurant in Harbin, China (-30°C winter) installed a run-around coil energy recovery system between the ESP exhaust and make-up air intake. The system captures 55% of exhaust heat, pre-heating -30°C outdoor air to -5°C before the main heating coil. Energy savings: approximately 35,000 kWh per heating season, payback in 3 years.
- Transfer air from dining room: A restaurant designed make-up air as 70% direct outdoor supply + 30% transfer air from the air-conditioned dining room (via transfer grilles in the kitchen wall). The strategy reduced the make-up air heating/cooling load by 30% compared to 100% outdoor air — and improved dining room comfort by creating positive pressure relative to outdoors (reducing drafts at entrance doors).
- Commissioning verification: An independent commissioning agent verified the make-up air system of a new restaurant kitchen. Key tests: (1) air balance measurement at all supply and exhaust points, (2) pressure differential between kitchen and adjacent spaces, (3) supply air temperature at diffusers, (4) smoke visualization of capture at hoods, (5) kitchen temperature mapping at cooking line. Three deficiencies were identified and corrected before the restaurant opened — avoiding post-opening complaints and retrofit costs.
