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Mechanical / HVACaka: heating ventilating and air conditioningaka: HVAC&Raka: mechanical systems

HVAC

In Plain English

The combined systems that heat, cool, and ventilate a building to keep occupants comfortable.

Definition

Heating, Ventilating, and Air Conditioning—the technology and systems that control the temperature, humidity, ventilation, and air quality within buildings. HVAC systems encompass all equipment and distribution systems for heating and cooling spaces and delivering ventilation air. HVAC design is governed by ASHRAE standards and local building codes.

Why It Matters in Bidding

HVAC is frequently one of the largest mechanical line items and a common source of bid spread because scope is split among equipment, ductwork, controls, and test-and-balance. Estimators must reconcile what the mechanical drawings, equipment schedules, and controls spec each cover so nothing falls between the HVAC sub and the electrical or controls subs, which is where costly post-award gaps appear.

Example

During scope review, the estimator confirms that the HVAC sub's bid includes test-and-balance and BAS controls wiring, then issues an addendum question because two of three bidders excluded controls, making their numbers look artificially low.

Related Terms

Frequently Asked Questions

Check controls and BAS integration, test-and-balance, startup and commissioning, roof curbs and structural support, smoke/fire dampers, line voltage versus low voltage wiring, and seismic restraints. These items are routinely excluded by one bidder and included by another, so a side-by-side scope sheet is essential before comparing HVAC numbers.
Differences come from equipment manufacturer substitutions, included versus excluded controls and balancing, labor productivity assumptions, and how each sub interprets ambiguous mechanical drawings. Without a leveling sheet, the lowest number often reflects missing scope rather than efficiency, exposing the GC to change orders after award.
Usually only the low-voltage controls wiring; line-voltage power to the units is typically the electrical contractor's scope. Estimators must define this division clearly in both bids so the disconnect, feeder, and final connection aren't double-counted or, worse, omitted by both trades and discovered during rough-in.

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