RTU (Rooftop Unit)
A packaged heating and cooling unit set on a building's roof.
Quick Answer
A rooftop unit (RTU) is a self-contained, factory-packaged HVAC unit installed on a roof or on a curb. It normally houses fans, coils, filters and a cooling and heating section in one cabinet and supplies air through ducts into the building. Estimators count RTUs EA by tonnage, then add the curb, the lift and the connections.
The Full Picture
An RTU puts most of the HVAC equipment for a zone or a building into one weatherproof cabinet. Depending on the model it holds the supply fan, the cooling coil, a compressor, a heating section, filters, and often an outdoor air hood with an economizer. It is common on one-story and low-rise commercial buildings such as retail, schools and offices because it frees interior space and needs no separate plant room. The unit connects to the building through supply and return ducts that drop through the roof, plus power, control wiring and, where required, gas piping and a condensate drain.
The mechanical plans show RTUs on a roof plan with a tag such as RTU-1, and the equipment schedule lists capacity, airflow, electrical data, weight, and options. Capacity is expressed in tons of cooling, where one ton is 12,000 BTU per hour. The schedule is the primary source for the count and the size of each unit, and details show the curb, duct connections and clearances. The specification, in Division 23, covers the equipment, controls, start-up and warranty. The structural drawings should show framing for the unit weight and the curb opening.
The takeoff unit is EA by tag, grouped by tonnage and by type, since gas-electric, heat pump and economizer options all change price. Items that tie to the unit are counted as their own lines: the roof curb or rails, the curb adapter when a new unit replaces an old footprint, a disconnect, the controls, thermostat or sensors, the duct connections and the roof penetrations or flashing. The crane lift is a separate cost. OSHA's crane rules in Subpart CC apply to power-operated equipment that can hoist, lower and horizontally move a suspended load, and assembly and disassembly of a crane has its own requirements, so the lift is planned and priced for the crane, the crew and the set-up time, not just the equipment weight.
Common mistakes are missing the curb, which may be furnished by the unit supplier or by the roofing contractor and is easy for both to assume the other has; pricing a lift by unit count when the picks are far apart or the roof access is poor; and skipping the roofer's work around the curb. On replacements, the old unit has to come out, so demolition, disposal, a possible curb adapter and the electrical reconnection belong in the number. Confirm weight against the structure, and carry the start-up and balance as separate lines.
Real Examples
Common Misconceptions
People assume: An RTU price is the unit price from the schedule.
Actually: The equipment is one line. The curb, crane, rigging, disconnect, controls, roof work, start-up and balancing are each separate, and on a small unit they can add up to a large share of the installed cost.
People assume: An RTU and an air handling unit are the same.
Actually: An RTU is a packaged unit that usually includes its own cooling and heating source. A typical air handling unit moves and conditions air using water or refrigerant supplied from a separate plant.
Does MeltPlan Solve This?
Partially — adjacentRTU tags, tonnages and curbs are counted from the plans, and MeltPlan's takeoff service covers that counting work: AI pulls quantities from plans and US-based experienced estimators review and adjust them. Crane selection, lift planning and roof coordination stay with your estimator and your mechanical subcontractor.
Get rooftop units and curbs counted from your plans →Frequently Asked Questions
What does RTU stand for in HVAC?
RTU stands for rooftop unit. It is a packaged HVAC unit that sits on a roof or a curb and serves the space below through ductwork.
How is an RTU taken off?
Count each unit EA from the equipment schedule and group them by tonnage and type. Then count the curbs, disconnects, controls and duct connections as their own items.
How many BTU is one ton of cooling?
One ton of cooling is 12,000 BTU per hour, so a 5 ton unit is 60,000 BTU per hour of cooling capacity.
Does the RTU estimate include a crane?
A crane or a lift is usually a separate line. It depends on unit weight, roof access and the number of picks, and it carries its own mobilization and planning.