Types

• Air Handling Units
  Central fan, coil, filter, and damper assemblies that condition and move air through ductwork, used in medium and large commercial and institutional buildings.
• Chillers
  Refrigeration machines that produce chilled water for building cooling, air-cooled or water-cooled, with scroll, screw, centrifugal, or magnetic-bearing compressors.
• Ductless Mini-Split Heat Pumps
  Inverter heat pumps with an outdoor unit piped to one or a few indoor heads, used to heat and cool homes, additions, and commercial rooms.
• Ductwork and Air Distribution
  Supply, return, and exhaust ducts with diffusers, grilles, dampers, and fittings, used to deliver and remove air from spaces in HVAC systems.
• Energy and Heat Recovery Ventilators
  Ventilation units that exchange heat (HRV) or heat and moisture (ERV) between exhaust and outdoor air, for efficient ventilation in homes and commercial buildings.
• Fan Coil Units
  Room-level units with a fan, filter, and chilled and hot water coils, used for zone heating and cooling in hotels, apartments, offices, and schools.
• Heat Pumps and Electrification
  Heat pump efficiency ratings and ENERGY STAR cold-climate criteria for replacing fuel-fired heating with electric heat pump systems.
• Hydronic Boilers
  Gas-fired or electric boilers that heat water for space heating systems, including condensing and non-condensing types, used in central plants for commercial and residential buildings.
• Rooftop Units
  Packaged rooftop HVAC units combining fans, cooling, heating, filters, and controls in one cabinet, used to condition low-rise commercial buildings.
• VAV Terminal Units
  Ducted terminal boxes that modulate supply airflow to each zone, with optional reheat and fans, used in variable air volume systems in commercial buildings.
• VRF Systems
  Variable refrigerant flow heat pump systems with outdoor units piped to many indoor units, used for zoned heating and cooling in offices, hotels, and multifamily.

Code reference

Always verify the adopted code edition and local amendments for the project jurisdiction.

Governing editions

Equipment access and location

• IMC 2024, Section 304.11: guards where appliances, equipment, fans, or other components requiring service are within 10 ft of a roof edge or open side more than 30 in. above grade; guards extend 30 in. beyond each end and do not pass a 21 in. sphere; anchorage per ANSI/ASSE Z359.1 is an exception (rooftop units, VRF systems, energy and heat recovery ventilators)
• IMC 2024, Section 306.1: appliances accessible for inspection, service, repair, and replacement, with a level working space at least 30 in. deep and 30 in. wide in front of the control side (all equipment)
• IMC 2024, Section 306.3: equipment in attics: passageway at least 30 in. high and 22 in. wide, not more than 20 ft long, with an opening at least 20 by 30 in. (ductless mini-split heat pumps, energy and heat recovery ventilators)
• IMC 2024, Section 306.5: permanent access to equipment on roofs or elevated structures more than 16 ft above grade; portable ladders not permitted; ladder side rails extend 42 in. above the roof edge (rooftop units, VRF systems, chillers)

Condensate

• IMC 2024, Section 307.2.1: condensate drain piping slope at least 1/8 in. per ft (fan coil units, air handling units, ductless mini-split heat pumps)
• IMC 2024, Section 307.2.3: auxiliary drain pan, secondary drain, or water-level detection where damage to building components could occur from overflow (fan coil units, air handling units, ductless mini-split heat pumps)

Ventilation and controls

• IMC 2024, Section 401.5: outdoor air intake openings protected with screens of specified mesh size (rooftop units, air handling units, energy and heat recovery ventilators)
• IMC 2024, Section 404.1: enclosed parking garage ventilation, with full operation at 0.75 cfm per sq ft and standby at 0.05 cfm per sq ft, and CO and NO2 detection per UL 2075 where controls are used
• IMC 2024, Section 405.1: systems controls for mechanical ventilation (all air-moving equipment)
• IECC 2024, Section C403: commercial HVAC efficiency, controls, economizers, energy recovery, and fan power; requirements depend on climate zone and system size (all types)

Duct systems

• IMC 2024, Section 602.2: materials exposed within plenums have a flame spread index of 25 or less and smoke-developed index of 50 or less (ductwork and air distribution, VAV terminal units)
• IMC 2024, Section 603.2: duct sizing per ACCA Manual D or ASHRAE methods (ductwork and air distribution)
• IMC 2024, Section 603.4: metallic ducts constructed per SMACNA duct construction standards (ductwork and air distribution)
• IMC 2024, Section 603.5: nonmetallic ducts listed to UL 181 as Class 0 or Class 1 (ductwork and air distribution)
• IMC 2024, Section 604.3: duct insulation and coverings with flame spread index 25 or less and smoke-developed index 50 or less (ductwork and air distribution)

Refrigeration

• IMC 2024, Chapter 11: refrigeration systems, including A2L refrigerants, refrigerant quantity limits, machinery rooms, and listed equipment per UL 484, UL/CSA 60335-2-40, and UL/CSA 60335-2-89; aligned with ASHRAE 15-2022 (VRF systems, ductless mini-split heat pumps, rooftop units, chillers)

Referenced standards

Sources

• UpCodes: 2024 IMC Chapter 3 general regulations (Department of Defense adoption; model-consistent provisions only), https://up.codes/viewer/department-of-defense/imc-2024/chapter/3/general-regulations
• UpCodes: 2024 IMC Chapter 4 ventilation, https://up.codes/viewer/department-of-defense/imc-2024/chapter/4/ventilation
• UpCodes: 2024 IMC Chapter 6 duct systems, https://up.codes/viewer/department-of-defense/imc-2024/chapter/6/duct-systems
• UpCodes: 2024 IMC Chapter 11 refrigeration, https://up.codes/viewer/department-of-defense/imc-2024/chapter/11/refrigeration
• ICC: 2024 International Energy Conservation Code, https://codes.iccsafe.org/content/IECC2024V1.0