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Mechanical / HVACaka: airside economizeraka: waterside economizeraka: free cooling

Economizer

In Plain English

An HVAC control that uses cool outdoor air to reduce or replace mechanical cooling when conditions allow.

Definition

An HVAC system component that uses outdoor air for free cooling when outdoor conditions are favorable, reducing or eliminating the need for mechanical refrigeration. Air-side economizers introduce large quantities of outdoor air through the air handler; water-side economizers use a heat exchanger to pre-cool condenser water using a cooling tower without operating the chiller. Economizers are required by energy codes in many climate zones.

Why It Matters in Bidding

Economizers are frequently mandated by energy codes, so an HVAC estimator who overlooks them risks a non-responsive bid that fails plan review or triggers a costly addendum. They also add dampers, sensors, controls, and larger air or water paths that carry real cost, making it important to identify the economizer type from the mechanical schedule rather than assuming a base packaged unit.

Example

Bidding a commercial rooftop replacement, an estimator confirms the local energy code requires air-side economizers, prices factory economizer packages and outdoor-air actuators on each unit, and notes the controls scope so the controls sub can coordinate.

Related Terms

Air HandlerChillerCooling TowerBuilding Automation System

Frequently Asked Questions

Many energy codes require economizers on units above a certain capacity in specific climate zones. Pricing a base unit without the economizer creates a non-compliant, non-responsive bid that fails inspection. Estimators verify the requirement from the mechanical schedules and specs so the right factory package and controls are carried from the start.
Air-side economizers add outdoor-air dampers, actuators, and larger intake openings to air handlers or rooftop units, generally a moderate first-cost add. Water-side economizers require a heat exchanger and integration with the cooling tower and chilled-water loop, often a larger and more coordination-heavy scope priced with the chilled-water system.
Economizer sequences usually fall to the controls or building-automation subcontractor, while the dampers and mechanical components belong to the HVAC contractor. Estimators must define the scope split clearly so sensors, actuators, and sequence-of-operation programming are not double-counted or, worse, left out of both bids.

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