Core HVAC System Requirements
Marriott MIDS (Mechanical Infrastructure Design Standards) sets stringent technical requirements for HVAC systems. Chiller integrated COP shall be no less than 6.3, and part-load IPLV no less than 10.5, which is far higher than the energy-saving evaluation value of GB 50189. Refrigerants must be environmentally friendly with GWP not exceeding 700. The chilled water system adopts Primary-Only Variable Flow design with a supply-return water temperature differential of 5.5–6.0°C. The cooling water system is designed with a 5°C temperature differential, and cooling tower approach shall not exceed 3°C. Guest room air conditioning adopts a four-pipe fan coil unit (FCU) system capable of simultaneous cooling and heating, with FCU noise in standard guest rooms not exceeding 28dB(A). The fresh air system adopts a Dedicated Outdoor Air System (DOAS), with guest room fresh air volume no less than 50m³/h per room and lobby fresh air volume no less than 30m³/h per person. All fresh air handling units must be equipped with energy recovery devices with sensible heat recovery efficiency no less than 65%. Air conditioning terminals adopt EC (electronically commutated) brushless DC motors for stepless speed control. The kitchen area is provided with an independent once-through air conditioning system maintaining negative pressure.
Electrical System and Emergency Power Requirements
MIDS standards have detailed tiered requirements for electrical systems. The power supply system shall adopt dual independent power sources, and transformers shall adopt N+1 redundant configuration. Emergency generator capacity must satisfy simultaneous operation of fire loads plus 50% of standby loads, with fuel storage sufficient for at least 72 hours of full-load operation (higher than the 3-hour requirement of GB 50016). Generators must auto-start and accept load within 10 seconds. UPS shall provide at least 60 minutes of backup time for ELV rooms and fire control rooms (higher than the national standard of 30 minutes). The lighting system requires overall lighting power density (LPD) to be at least 15% lower than the ASHRAE 90.1 baseline. Guest room lighting adopts stepped dimming control providing four scene modes: reading, leisure, sleep, and night light. The emergency lighting system meets NFPA 101 life safety code requirements. ELV systems shall include structured cabling (Category 6 or above), building automation system (BAS based on BACnet protocol), room control unit (RCU), and energy management system (EMS). MIDS requires the BAS to monitor energy consumption data of all MEP equipment and generate monthly energy reports.
Plumbing and Fire Protection System Technical Requirements
The most prominent MIDS plumbing requirement is 5-second hot water delivery—the time from opening the hot water tap to the water temperature reaching 49°C shall not exceed 5 seconds. This means the hot water circulation system requires refined design: circulation pump flow is determined to ensure 5-second hot water delivery, return pipes are provided with thermostatic valves to ensure uniform circulation across branches, and pipe insulation thickness is increased by 20% over the national standard. Domestic hot water is maintained at 60°C with a high-temperature disinfection function in storage tanks (once weekly at 74°C for 30 minutes) to kill Legionella. The water supply system's vertical zoning pressure shall not exceed 0.45MPa. Sanitary fixtures must be water-efficient—toilets not exceeding 4.0L per flush, faucets not exceeding 5.0L/min. The fire protection system must meet NFPA 13 (automatic sprinkler), NFPA 14 (standpipe systems), and NFPA 20 (stationary fire pumps) standard requirements while complying with local fire codes. The automatic sprinkler system covers all hotel areas including guest room wardrobes, public areas, and back-of-house areas.
MIDS Audit Process and Compliance Requirements
MIDS standard implementation is carried out through two phases: project design review and site inspection. In the design review phase, the following documents shall be submitted to Marriott Asia-Pacific Engineering Department after schematic design completion: a Compliance Matrix cross-referencing all clauses of the 12 MIDS volumes with compliance status marked item by item; an ASHRAE 90.1 energy simulation report demonstrating energy consumption at least 10% below baseline; technical specifications for all equipment with budget parameters meeting MIDS minimum requirements; and water system calculations verifying 5-second hot water delivery. The site inspection phase is conducted by a third-party plan review agency designated by Marriott: Shop Drawing Review, Factory Witness Testing, Site Inspection during installation, and Commissioning Witness. Key equipment brands must be on Marriott's Pre-approved Brand List, including chillers, cooling towers, pumps, boilers, generators, and switchgear. Any design change deviating from MIDS standards requires submission of a Variance Request and written approval from Marriott's Director of Engineering.