HVAC Scope of Work: Equipment Schedules, Ductwork Sealing, and TAB Reports

An HVAC scope of work template that's generic is worse than useless — it gives the impression of completeness while leaving the real gaps unaddressed. HVAC is the trade where split responsibilities between the HVAC sub, the controls sub, the electrical sub, and the plumbing sub create the most expensive disputes. This guide is an HVAC scope of work template for commercial GCs, organized by the sub-trade specific requirements, package items, and the coordination requirements that define trade boundaries.

HVAC Equipment Supply and Installation

Tip: The best GCs specify every piece of HVAC equipment by tag number, not just by type. Tags create accountability — "RTU-1" cannot be omitted the way "one rooftop unit" can be quietly excluded.

• Rooftop units (RTUs): Specify each unit by tag, cooling capacity (tons or kW), heating capacity (kW or MBH), supply airflow (L/s or CFM), efficiency rating (EER, SEER, IEER per ASHRAE 90.1), and BMS integration protocol (BACnet or Modbus). Roof curbs — specify whether furnished by the RTU manufacturer or fabricated by the sheet metal sub. Confirm minimum ventilation rates per ASHRAE 62.1.
• Split systems: Specify indoor unit type (cassette, wall-mount, ducted), outdoor unit location, refrigerant line set length and routing, and maximum allowable line set length per manufacturer specifications. Exceeding manufacturer's maximum line length requires additional refrigerant charge — this must be in scope explicitly.
• VRF/VRV systems: Specify number of outdoor condensing units, number and type of indoor units, refrigerant piping configuration (2-pipe vs. 3-pipe heat recovery), BMS integration, and commissioning requirements. VRF systems require a factory-authorized start-up — specify it. Most VRF manufacturer warranties are void without factory commissioning documentation.
• Air handling units (AHUs): Specify AHU tag, supply airflow, heating and cooling coil capacities, filter section type (and MERV rating per ASHRAE 52.2), economizer requirements per ASHRAE 90.1, and supply air temperature setpoints. For custom AHUs, specify casing construction (double-wall vs. single-wall) and thermal break requirements for units in unconditioned spaces.
• Fan coil units: Specify by tag, pipe configuration (2-pipe or 4-pipe), cooling and heating capacities, airflow, filter type, drain pan depth and material, and whether auxiliary drain pans are required above sensitive ceiling areas.
• Unit heaters and radiant panels: Specify by tag, heat output (kW or MBH), fuel type, and mounting configuration. Specify hydronic unit heaters vs. electric — do not leave the choice to the sub.

Ductwork

• Construction standard: SMACNA HVAC Duct Construction Standards — specify pressure class (typically Class 2" w.g. for low-pressure supply; Class 3" w.g. for return and exhaust). Sheet metal gauge must follow the SMACNA table, not the sub's preference.
• Sealant class: Specify SMACNA Seal Class A for all supply ductwork (all transverse joints, longitudinal seams, and all connections) for ASHRAE 90.1 compliance. Class C (transverse joints only) on supply systems is insufficient for energy code compliance on most commercial projects.
• Duct liner: Specify internal duct liner requirements — acoustic liner on first 3m of supply and return ductwork from each AHU. Note: internal liner is not appropriate in high-humidity applications (kitchen exhaust, pool exhaust) — specify external insulation in those zones.
• Flexible ductwork: Maximum 1.8m (6 ft) length for any flexible duct connection to a diffuser per SMACNA. Flexible duct run fully extended — sagging flex duct increases static pressure and reduces airflow. Require inspection before ceiling closure.
• Fire and smoke dampers: At every duct penetration of a fire-rated wall or floor assembly per the IBC. Specify UL/ULC listing, actuator type (spring-return for smoke dampers), and the sub's responsibility to provide access doors at each damper location for inspection and reset per NFPA 80 and NFPA 105.

Refrigerant Systems

• Pipe sizing and routing: Sub provides refrigerant pipe sizing calculations confirming suction and liquid line sizes are within manufacturer's allowable range for the actual installed length and elevation change. Do not accept field sizing without documentation.
• Pressure testing: Pressure test all refrigerant piping to the manufacturer's required test pressure (typically 1.5× MAWP for the refrigerant used) using dry nitrogen. Electronic leak test after pressure test before charging. Test records required.
• Refrigerant charge: System charged to manufacturer's specified weight. Weigh-in method required — not "charge to operating superheat and subcooling" without recorded charge weight. Required for warranty compliance on most VRF and split system manufacturers.
• Refrigerant detection: Required by ASHRAE 15 (and CSA B52 in Canada) in mechanical rooms or enclosed spaces containing refrigerant-containing equipment. Specify sensor type, alarm setpoints, and tie-in to BMS. This is omitted on more than half of HVAC scopes — and flagged at final occupancy inspection.

Testing, Adjusting, and Balancing (TAB)

• TAB responsibility: Specify whether TAB is performed by the HVAC sub's own AABC- or NEBB-certified technician or by an independent TAB firm. Independent TAB is strongly recommended on projects with a commissioning authority. All airflows balanced to ±10% of design.
• TAB report: Required at closeout — must include design vs. actual airflow for every diffuser, grille, and terminal unit in the building. Without this report, HVAC systems that are out of balance will generate comfort complaints and energy waste. Most AHJs and commissioning agents require the TAB report before occupancy.
• Hydronic balancing: If hydronic HVAC systems are in scope, specify flow measurement and balancing at each terminal unit and coil. Balancing valves must be tagged and set position recorded.

• Equipment start-up and commissioning: Factory-authorized start-up is required for all VRF systems, large chillers, high-efficiency boilers, and energy recovery ventilators. Specify that start-up documentation (factory commissioning reports, refrigerant charge records, warranty registration) is a closeout deliverable.
• Filter media at substantial completion: Specify that all HVAC equipment is fitted with new, clean filter media at substantial completion — not the construction-phase filters that were installed during building work. Specify MERV rating per ASHRAE 52.2 for each unit type.
• Vibration isolation: Spring isolators and inertia bases for all rooftop and mechanical room equipment. Specify isolation efficiency requirement (typically 98% for rotating equipment on occupied floors). Flexible canvas connections at all AHU and fan duct connections. This is frequently omitted as a cost-saving measure — specify it explicitly.
• Permits and gas inspections: HVAC sub obtains and pays for all mechanical permits. Gas piping pressure tests are witnessed by the gas utility inspector — sub schedules and attends. Gas permits are separate from mechanical permits in most jurisdictions.
• Hoisting and rigging: Crane costs for setting rooftop equipment are the HVAC sub's responsibility unless explicitly stated otherwise. On urban projects with restricted crane access, specify that the sub provides a rigging plan and crane logistics plan before mobilization.
• Temporary heat: If the GC schedule requires temporary heating during construction, it must be an explicit line item. It is not automatically in the HVAC sub's scope.
• Drip pans: Provide auxiliary drip pans beneath all fluid-conveying equipment located above electrical equipment, server rooms, or occupied finished ceiling areas. Required by most electrical codes for equipment above electrical panels.

• Electrical: Power supply to each HVAC unit — confirm voltage, phase, ampacity, and whether a disconnect switch is by the electrical sub or by the HVAC sub. VFDs for variable-speed fans and pumps — must be ordered with BACnet communication cards. Confirm who supplies, installs, and programs VFDs. After-the-fact BACnet card additions to VFDs can cost more than the VFD itself.
• Controls/BMS: Thermostat and sensor wiring: confirm which trade provides the wiring from thermostats and sensors to HVAC equipment controllers. HVAC sub typically provides equipment controllers and wiring within equipment; controls sub provides BMS points and integration wiring. Define the interface point in both subcontracts.
• Plumbing: Condensate drain connections from all HVAC equipment to the nearest floor drain or drain stub-out provided by the plumbing trade. Confirm condensate drain locations and invert elevations before HVAC equipment is set. Make-up water connections for humidifiers and hydronic systems — confirm the plumbing sub provides the connection point.
• Structural: Equipment operating weights must be confirmed with the structural engineer before any rooftop equipment is ordered. Dunnage frames (steel support rails for rooftop equipment) — confirm whether provided by the structural sub, the HVAC sub, or the steel sub. Spring-isolated rooftop equipment requires a different dunnage configuration than rigidly mounted equipment.
• Architectural: Ceiling types in all areas must be confirmed before diffuser frames are ordered — T-bar vs. drywall frames are different products with different lead times. Louver sizes and locations must be confirmed on architectural elevations before penetrations are made in the building envelope.
• Roofing: All roof curbs and penetrations must be coordinated with the roofing sub before the roofing membrane is installed. The roofing sub typically installs the curb flashing; the HVAC sub sets the equipment on the curb. Confirm this sequence and the flashing responsibility in both subcontracts.