Project Delivery Method: Design-Bid-Build (D-B-B)

Owner Team: Commercial property management owner, owner representative (consultant), capital projects manager, and a facility manager (out-source staff)

Project Delivery Team: D-B-B project manager; job superintendent; mechanical-electrical coordinator; equipment manufacturer technician; and architect, acoustical, plumbing, electrical, structural, fire protection, and security consultants 

HVAC Project Team: HVAC project manager subcontractor; building automation systems technician subcontractor; third-party commissioning consultant (CxC); and testing, adjusting, and balancing (TAB) technician 

Application: 2019 ASHRAE Handbook, “Commercial and Public Buildings,” Chapter 3, and “Data Centers and Telecommunication Facilities,” Chapter 20

Systems: 2020 ASHRAE Handbook, “HVAC System Analysis and Selection”

Project Type: Tenant fit-out

References: 2019 ASHRAE Handbook, “HVAC Applications;” 2020 ASHRAE Handbook, “HVAC Systems and Equipment;” and, for additional reference, view the codes and standards portion located at the back of each ASHRAE Handbook

Other References: ASHRAE GreenGuide: “Design, Construction, and Operation of Sustainable Buildings;” “ASHRAE UFAD Guide and O&M Guide Set;” “ASHRAE Humidity Control Design Guide for Commercial and Institutional Buildings;” ASHRAE Standard 90.4, “Energy Standards for Data Centers;” and ASHRAE Standard 202, “Commissioning Process for Buildings and Systems”



  • The HVAC system selection and design intent is based on the process outlined in ASHRAE Handbook 2020, Chapter 1, “HVAC System Analysis and Selection,” and includes the following:
    • Building owner’s program goals and any additional goals 
    • System constraints and constructability constraints
    • The finalized system selection shall be a decentralized HVAC system with decentralized HVAC air systems and terminal units with central plant heating and central plant air conditioning
    • Specialized systems shall include a data center within an existing building
    • Automatic controls shall include temperature controls, equipment furnished controls, a BACnet interface, an internet interface, an existing BAS interface, and an existing computerized maintenance management software (CMMS) system interface
  • Program and Project Goals
    • Functional goals: (refer to Chapter 1, 2020 Handbook)
    • Budget goals: first cost
    • Timeline goal(s): occupancy due date 
    • Management goals: property management and out-source mechanical and electrical services via a service contract
  • Available Utilities
    • Electrical power, emergency power, and central plant chilled process water 
    • Central air system(s) and supply air for ventilation
    • Central air systems: new underfloor supply air plenum with constant air volume, fixed return air (RA) flow to a computer room air conditioning (CRAC) unit mounted intake plenum, and air filters are MERV 14 in the new CRAC units 


  • The HVAC design criteria shall be in sync with the project delivery method and the owner’s project requirements 
  • A decentralized heating and cooling system shall consist of four CRAC units and two CRAC standby units with underfloor discharge air to the raised computer room space and equipment. Each unit shall be 20 ton with electric reheat and distilled water humidifiers to maintain 75°F and 50% relative humidity 24 hours a days and fitted with a MERV-14 filter. 
  • Raised floor 2-by-2-foot floor tiles shall be coordinated in anticipation of the data center equipment’s arrival. The underfloor supply air shall also be provided directly below specific pieces of computer equipment.
  • Each CRAC unit shall be served by an existing chilled water supply and return pipes for tenant use from the existing air-cooled chiller on the roof operating year-round. 
  • The design team shall provide contract drawings and specifications coordinated with equipment weight; electric data, including emergency power requirement; and plumbing criteria to solicit general contractor bids.
  • Field fabrication drawings shall become the record drawings at closeout.
  • CRAC units shall be furnished with operation and maintenance (O&M) manuals. The preventive maintenance work orders shall be uploaded to the outsource O&M contractor’s computerized maintenance management software (CMMS) system.
  • The D-B-B contractor shall provide system training to the building’s O&M staff regarding the air conditioning, humidification, and electrical systems.

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