Every building needs conditioned air, but not every building needs the same system. The HVAC system an architect selects shapes the building in ways that outlast the initial design decision: it determines floor-to-floor height, dictates ceiling plenum depth, drives first cost and operating cost, and constrains what's possible in mechanical rooms and shafts.

The core HVAC families you need to know for the ARE are variable air volume (VAV) systems, variable refrigerant flow (VRF) systems, fan coil units (FCU), radiant heating and cooling, packaged rooftop units (RTU), and dedicated outdoor air systems (DOAS). Each has a different operating principle, a different spatial footprint, and a different sweet spot for building type and climate.

Selection is never a single-variable problem. A system that delivers excellent energy performance might be too expensive for the construction budget. A system that fits the program might struggle in the local climate without supplemental dehumidification. A system that works beautifully in an office tower becomes impractical in a 20,000-square-foot K-12 school.

NCAR Objective 3.1 asks you to evaluate these systems against real criteria: function, cost, size, availability, programmatic needs, and energy and water usage. That means you need to understand not just what each system does but when to choose one over another, and what tradeoffs you're accepting when you do.