Where AHU energy actually goes — and what a closed loop recovers

In a typical commercial building, HVAC is the largest energy consumer, and the air handling units are where most of that energy is spent — fan power to move air, and cooling energy to condition it. The waste hides in one place: the gap between what the building needs right now and what static setpoints assume it needs.

The physics of the waste

Fan power scales roughly with the cube of speed. Run a fan at 80% of the speed the moment actually requires and you spend about half the energy of running it at 100%. That cube law is why over-delivery is so expensive: a duct static pressure setpoint chosen for the worst summer afternoon quietly taxes every mild morning of the year. Cooling is the same story — chilled-water valves held open for a design-day load keep overcooling long after the load has fallen away.

Why commissioning-day setpoints decay

• Loads move: occupancy patterns, tenant churn, and weather never match the assumptions the setpoints were tuned for.
• Equipment drifts: sensors go out of calibration, filters load up, coils foul — the plant the rules were written for no longer exists.
• Nobody retunes: re-commissioning is periodic at best; the building operates on stale assumptions between visits.

None of this is operator failure. A human team cannot re-derive optimal setpoints for dozens of AHUs every few seconds. It's a control-loop problem, and it needs a control-loop answer.

What closing the loop recovers

A closed-loop system estimates, from physics, what each AHU should be doing given the live load, occupancy, and weather — then writes the setpoints that close the gap at the lowest energy, continuously. Comfort is a constraint, not a casualty: occupied spaces hold their ~24°C setpoints throughout; the savings come from delivering exactly the airflow and cooling the moment requires, not from letting spaces drift.

In our reference deployment — 68 AHUs across roughly 550,000 sq ft, running autonomously for over 12 months — that recovered 17–22% of HVAC energy in the first year, with zero comfort or safety incidents. No new chillers, no new sensors, no capex: the same equipment, operated continuously instead of statically.

How to size the opportunity in your building

A quick field test: trend one AHU's supply fan speed and valve position over a mild week. If the fan hardly modulates while the load clearly does, the cube law says you're paying for air nobody asked for. That gap — visible in a week of trend data — is what a closed loop is built to close.