Project Delivery Method: Construction management at risk (CM) with guaranteed maximum price (GMP)

Project Type: Construction renovation

Owner Team: The data center owner, owner representative (consultant), project manager of capital projects, and facility manager

Project Delivery Team: CM project manager, mechanical-electrical coordinator, and security consultants

HVAC Project Team: HVAC project manager; automatic temperature control (ATC) technician subcontractor; sheet metal subcontractor; third-party commissioning consultant (CxC); and third-party testing, adjusting, and balancing (TAB) technician

Application 2023 ASHRAE Handbook: Chapter 20, Data Centers and Telecommunication Facilities

Fundamentals 2021 ASHRAE Handbook: Chapter 20, Space Air Diffusion, and Chapter 21, Duct Design

HVAC Systems and Equipment 2020 ASHRAE Handbook: Chapter 4, Air Handling and Distribution

References: Construction Management Association of America (CMAA)

Other References: ASHRAE Underfloor Air Distribution (UFAD) Guide and UFAD Operation and Maintenance (O&M) Guide, ASHRAE Standard 202 (commissioning process for buildings and systems), and ASHRAE standard practice for inspection and maintenance of commercial building HVAC systems


  • This optimum HVAC system selection and the project’s design intent is based on the analytical process outlined in ASHRAE Handbook 2020, Chapter 1, HVAC System Analysis and Selection (refer to this month’s Tomorrow’s Environment column) and includes the following:
    • Owner’s project requirements (OPR), building program goals, and additional goals
    • The finalized system selection shall be a new central AHU with return air-exhaust air economizer to provide HVAC comfort to a previous data center raised-floor computer space adjacent to an existing raised floor computer room
    • New system automatic controls shall be interfaced with the existing building automation system (BAS) controls, equipment furnished controls, BACnet interface, internet interface, and populating new equipment data into the existing computerized maintenance management software (CMMS) system from in-house operation and maintenance (O&M) staff
  • Program and Project Goals:
    • Functional Goals: (refer to Chapter 1, 2020 Handbook)
    • Budget Goals: First cost and operating cost
    • Timeline Goal(s): Installation due date and pre-purchased equipment date
    • Management Goals: Data center management, in-house mechanical and electrical services for new equipment, and capital projects management
  • Available Utilities: Existing electrical service, central chilled water supply and return (CHWS and CHWR) and hot water supply and return (HWS and HWR), and the BAS
  • Chilled Water and Hot Water Pipe Distribution: Schedule 40 black iron steel with fiberglass insulation per the state energy code
  • Air System: A new single-zone, UFAD system serving 4,000 square feet of interior renovated raised floor space
  • Pumps: A new in-line circulator with an additional standby pump, each with its own variable-speed drive (VSD) drive


  • The HVAC BofD criteria shall be in sync with the project delivery method and aforementioned OPRs
  • The utility shall consist of the existing electrical 480-V power
  • Existing CHWS, CHWR, HWS, and HWR shall be connected to a new single-zone UFAD unit. The chiller and boiler already exist. In-line circulators with associated standby pumps shall serve UFAD unit heating and cooling coils with new VSD, in lieu of ATC valves at the coils
  • Air distribution from the UFAD system shall be directed into a 15-inch underfloor air plenum. Each office cubicle a floor supply air register shall be located to provide spot heating, cooling, and ventilation. Return air ductwork, evenly distributed over the 16 work cubicles, shall draw back 80% of the supply air leaving the office space under a positive pressure
  • Airside Economizer: Return air/exhaust fan shall operate based on enthalpy controls discharging the air back to the UFAD unit or discharging the return air to outdoors
  • New UFAD unit shall be furnished with MERV-14 filters upstream of the heating and cooling coils and fan section
  • Sheet Metal: Shall be sealed on the supply air distribution. The UFAD plenum shall be sealed (pipe, electrical, and cable penetrations in and out of the raised floor) and pressure tested for 1-inch positive pressure
  • The UFAD system (air and water) shall be tested, adjusted, and balanced by a TAB technician and commissioned by the commissioning agent
  • Conceptual/Schematic Phase General Notes:
    • The HVAC design engineer shall provide system flow diagrams with the OPR, DID, and BofD along with ATC sequences of operation that are integrated with the existing BAS control system and electrical one-line diagram
    • The HVAC design engineer shall include an electrical data sheet to coordinate with the electrical design engineer and a plumbing data sheet to coordinate with the plumbing design engineer

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