Skip to main content
Back to Glossary
Mechanical / HVACaka: RTUaka: rooftop package unitaka: commercial rooftop unit

Rooftop Unit

In Plain English

A self-contained heating and cooling unit mounted on the roof that connects to the building's ductwork below.

Definition

A packaged HVAC unit installed on the roof of a building that provides heating, cooling, and ventilation through an internal duct distribution system. Rooftop units (RTUs) are among the most common HVAC systems for low-rise commercial buildings due to their low first cost, simple installation, and easy rooftop service access. They may be single-zone or multi-zone and may include gas heat, electric heat, or heat pump heating.

Why It Matters in Bidding

RTUs are frequently the largest single line item on a commercial HVAC bid, and their long lead times make them a scheduling and cash-flow risk an estimator must flag. Beyond the unit price, the bid must capture roof curbs, structural support, crane/rigging, gas and electrical connections, and controls integration, which are easy to overlook when pricing only the equipment.

Example

A mechanical estimator pricing a strip-mall buildout carries five 5-ton packaged RTUs plus roof curbs, a one-day crane rental for set, and the associated gas, electrical, and economizer controls in the bid.

Related Terms

Frequently Asked Questions

Carry roof curbs or rails, structural curb adapters, crane and rigging for the lift, ductwork transitions, gas piping, electrical disconnects and feeders, condensate, and controls or building-automation integration. Roofing patch-in around the curb may belong to another trade, so clarify scope splits to avoid gaps or double-counting.
Packaged units, especially larger tonnages or units with special options, can carry long manufacturer lead times that affect the project schedule and your procurement cash flow. Estimators should note lead times in the proposal, lock pricing where possible, and account for potential escalation or substitution if the awarded schedule slips.
Tonnage comes from the engineer's load calculation or equipment schedule, not from rules of thumb at bid time. Estimators bid the units and capacities shown on the mechanical schedule and drawings. If you must value-engineer, propose an alternate that meets the specified capacity and efficiency rather than guessing at size.

Need more than definitions?

Get AI-powered bid alerts, automated form filling, and proposal drafting.

Start Free Trial

© 2026 ConstructionBids.ai — A LaderaLabs Product