What balanced air looks like
A correctly balanced commercial kitchen runs slightly negative at the hood plane (in the −0.01 to −0.03 inch-water-column range) and very close to neutral at the front door of the dining room. The air the exhaust fan pulls out has to come from somewhere; if it does not come from the makeup-air unit, it comes through the dining room and the entry vestibule. That is why your dining room is freezing in February even though your thermostat says 71°F.
The reference standard is ASHRAE 154-2024, which gives sizing and pressure-balance targets for commercial kitchen ventilation. The target we hold to is conservative compared to ASHRAE because Houston has long, hot, humid summers and the cost of pulling unconditioned air across the dining room is real, both in customer comfort and in the operator's electricity bill.
How we measure
We map static pressure at three points on the line, three points around the dining-room boundary, and one point at the front door. We use a Dwyer Magnehelic series 2000 differential gauge for the hood plane and a digital manometer for the slower-moving door measurements. Readings are taken with the kitchen at representative load — not at idle, and not at peak.
What we adjust
Three things. The makeup-air unit's belt and sheave — most commercial-grade MUAs are belt-driven, and an old belt slips enough to drop CFM by ten to fifteen percent without anyone noticing. The MUA's outdoor-air damper — these get stuck on the linkage, especially on coastal-air units that see salt-laden humidity twelve months a year. The exhaust-side damper on the roof — adjustable on most commercial systems, and surprisingly often set wrong by the original installer.
Where the MUA is undersized for the load — a common condition on retrofits where the kitchen has expanded since the original install — we will quote a replacement unit. We do not sell the unit. We coordinate with a TDLR-licensed installer.
Why we do this seasonally and not quarterly
Two reasons. First: a small Houston kitchen will see its makeup-air conditions shift twice a year — at the start of the long humid summer and at the start of the cool winter. Each shift can change the indoor-outdoor pressure differential at the front door by enough to matter. Second: balancing is most usefully done after a season of operation, not after a single quarter; we have more data to read.
What we will tell you in the report
One number for the hood plane. One number for the dining-room boundary. One number for the front door. A flag list. A recommendation. Photographs of the MUA's belt and the rooftop damper. Total readout: one page of pascals and inches-water-column with one paragraph of plain English at the bottom.