Quick answer
- Exhaust CFM without equal (or designed) replacement air creates pressure and smoke problems.
- Tempered MUA is often required for comfort and code — do not assume raw outdoor air is enough.
- Coordinate hood, MUA, and dining HVAC so one system does not fight the others.
When this applies
New hood or exhaust upgrade
You are adding a cook line, replacing a hood, or upsizing exhaust. MUA capacity and tempering must be resized with the exhaust, not guessed from the old RTU.
Dining room comfort complaints during service
Drafts, hot/cold swings, or hard-to-open doors during peak kitchen hours often point to pressure imbalance from missing or undersized MUA.
Health department or inspector flags
Smoke escape, grease, or ventilation notes on inspection reports — treat as a system balance issue, not only a hood cleaning issue.
How it works
Match exhaust and makeup as a pair
Start from hood design CFM and capture requirements. Size MUA to replace exhausted air per the design method (dedicated MUA unit, transfer air strategy, or approved combination). Document assumptions so the GC and mechanical bids align.
Decide tempering and delivery location
Untreated outdoor air can wreck kitchen and dining comfort in Central Valley summers and cool South Bay evenings. Tempered MUA, diffuser placement, and interlocks with the exhaust fan are part of the design — not optional finish work.
Commission pressure and interlocks
At start-up, verify fan interlocks, MUA flow, and building pressure under cooking and idle modes. Adjust so the hood captures without starving the dining HVAC.
Failure modes to avoid
Relying on the dining RTU as makeup air
Comfort units are rarely sized or ducted to replace kitchen exhaust. The result is negative pressure, smoke spill, and comfort complaints.
Installing MUA without tempering or controls
Raw OA dumps create cold kitchens in shoulder seasons and overload AC in summer. Spec tempering and exhaust-tied controls.
Ignoring grease, clearances, and roof penetrations
MUA and exhaust roof work must respect fire clearances, grease duct rules, and roofing warranties. Late field changes are expensive.
Proof & local context
- • We coordinate restaurant HVAC and makeup air for light commercial kitchens in San Jose / South Bay and Central Valley markets.
- • Bids call out MUA tempering, interlocks, and pressure goals so exhaust upgrades do not orphan the dining room.
- • CSLB #1056688 · bilingual crews · Perfection Guaranteed.
Next step
Guidance reflects light-to-mid commercial HVAC, refrigeration, and server/edge cooling practice across San Jose / South Bay and Central Valley (Hanford, Clovis) jobs. Not for hospitals or hyperscale data centers. Confirm site conditions, Title 24 path, and manufacturer data before bidding.
FAQs
Can we transfer air from the dining room instead of dedicated MUA?
Sometimes, within design and code limits — but only when engineered. Transfer air is not a free substitute for a properly sized MUA strategy on high-exhaust kitchens.
Does MUA need heating and cooling?
Many California restaurant projects need tempered MUA for staff comfort and to avoid overloading dining HVAC. Exact tempering depends on climate, exhaust rate, and design.
Who designs the hood vs. the MUA?
Hood manufacturers and kitchen designers often set exhaust; mechanical design must close the air balance. Require a single responsible narrative in the RFP so responsibility is clear.