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Proposed ASHRAE 90.1 – 2007 Addenda for Data Centers

Introduction: In working on the up-coming LEED Data Centers standard, I needed to take a deep dive into the proposed changes to the ASHRAE 90.1 energy standard. The good news here is that the revised 90.1 standard, to be released this year (2010), will contain very specific language on minimum energy efficiency requirements for data centers. Prior to this, there was really nothing in the standard that discussed how to apply the requirements to data centers, which often caused difficulties in showing conformance with the energy standard.

However, there is still no mention of electrical system efficiency requirements in the proposed addenda from ASHRAE. This is necessitating writing a new procedure to determine minimum electrical system efficiency based on UPS technology, reliability level of the facility, PDU efficiency, etc. More to come on that later.

 Part 1: Overview definitions and system fan power calculations

Items from Addendum cj and bu:

Overarching rules

  • A data center (ASHRAE uses the term computer room throughout the 90.1 document) is defined as room with a load of 20 watts/SF across the conditioned floor area

  • Air conditioning units serving a data center are covered by ASHRAE Standard 127, specifically table 6.8.1H

  • Air or water economizer is required except:

  • o tier IV facilities (as defined by TIA 942 standard)

  • o data centers with a cooling load less than 880 kW and which are not served by a central chilled water plant

  • o data centers with a load less than 175 kW and are served by a central chilled water plant

  • o local authority does not allow a cooling tower

  • o data centers with a load less than 175 kW being added on to a larger facility

  • o greater than (or equal to) 75% of the total load is for an essential facility (defined in the Addendum) such as fire and police facilities, emergency communications centers, critical national defense facilities, data centers in the financial sector providing core clearance and settlement services

  • Water economizer for data centers must cover 100% of the load starting at outdoor conditions of 40F dry bulb and 35F wet bulb temperatures

  • Normative references:

  • o ANSI/ASHRAE Standard 127-2007 Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners

  • o ANSI/TIA-942- 2005 Telecommunication Infrastructure Standard for Data Centers

  • o The Interagency Paper on Sound Practices to Strengthen the Resilience of the US Financial System, April 7, 2003

  • o NFPA 70 Article 708 -2008 - Critical Operations Power Systems(COPS)

Definitions of baseline

  • Small data centers - baseline is air-cooled DX systems - use system 3 or 4 for baseline system as defined in table G3.1.1B

  • Large data centers - baseline is central plant, chilled water with CRAHs and VAV controls - use system 9 for baseline system as defined in table G3.1.1B

  • Large data centers have loads greater than 166 tons or 50 tons if the data center is located in a larger building with a central chilled water system

Fan Power Calculations - the following are functions written in VBA for Microsoft Excel. They are based on the formulae in the ASHRAE documents. With these functions a user will be able to determine the maximum allowable fan brake horsepower of the fans based on the total supply air volumetric rate. Also, based on the brake horsepower, the minimum motor efficiency can be determined. Finally, based on part load, the user will be able to determine the system fan power at part load.

For systems 3 and 4


  • This function calculates the minimum fan efficiency for systems 3 and 4 based on ASHRAE 90.1-2007 table 10.8. Systems 3 and 4 are baseline systems based on DX rooftop units

  • Fan_Motor_Efficiency_System_3_4 = (0.0242 * (Log(System_3_4_BHP) / Log(2.718282))) + 0.834


  • This function calculates the maximum allowable brake horsepower for systems 3 and 4

  • Fan_BHP_per_CFM_System_3_4 = (0.00094 * System_3_4_CFM)


  • This function calculates the maximum allowable system fan power in kW

  • System_Fan_Power_System_3_4 = (System_3_4_BHP * 746/ Fan_Motor_Efficiency_System_3_4) / 1000

For system 9


  • This function calculates the minimum fan efficiency for system 9 based on ASHRAE 90.1-2007 table 10.8. System 9 is a baseline system based on a chilled water plant

  • Fan_Motor_Efficiency_System_9 = (0.0242 * (Log(System_9_BHP) / Log(2.718282))) + 0.834


  • This function calculates the maximum allowable brake horsepower for system 9

  • Fan_BHP_per_CFM_System_9 = (0.00062 * System_9_CFM)

System_Fan_Power_System_9(System_9_BHP, Fan_Motor_Efficiency_System_9)

  • This function calculates the maximum allowable system fan power in kW

  • System_Fan_Power_System_9 = (System_9_BHP * 746 / Fan_Motor_Efficiency_System_9) / 1000

For all systems


  • This function calculates fan power at part load based on ASHRAE 90.1-2007 Table G3.1.3.15

  • System_Fan_Power_Fraction_at_PLR = (0.0013 + (0.147 * Fan_System_Part_Load_Ratio) + (0.9506 * Fan_System_Part_Load_Ratio ^ 2) - (0.0998 * Fan_System_Part_Load_Ratio ^ 3))

Proposed ASHRAE 90.1 - 2007 Addenda for Data Centers - Part  2: Additional Information and Energy Modeling Parameters

This is a high-level summary of the major items contained in the current addenda cj and bu: (Please note that the items listed are the changes proposed in the addenda that apply to data centers only. Additionally, they do not contain all of the language necessary to verify compliance with the ASHRAE 90.1-2007 standard).

Items from Addendum cj and bu:

Exception G3.1.1

  • This was the exception that data centers would fall under prior to these addenda. This no longer applies.


  • Outdoor air economizers shall be included in baseline HVAC Systems 3, 4 and 9 (the systems used for data centers) based on climate as specified in Table G3.1.2.6A.

  • Exceptions to G3.1.2.6: Economizers shall not be included for systems that include gas-phase air cleaning to meet the requirements of Section 6.1.2 of ANSI/ASHRAE Standard 62.1. This exception shall be used only if the
    system in the proposed design does not match the building design.

  • Systems that serve computer rooms that are HVAC System 3 or 4 shall not have an economizer.

  • Systems that serve computer rooms that are HVAC System 9 shall include an integrated water-side economizer meeting the requirements of Section in the baseline building design.

  • If the simulation software cannot model an integrated water-side economizer, then an air-side shall be modeled.


  • If the proposed building has humidification, the set points and schedules shall be the same in both the baseline and proposed buildings

(Note: this provision will only allow for savings if the proposed building uses a more energy efficient humidification process, such as adiabatic as compared to isothermal).

Energy Modeling Parameters

Type and Number of Chillers

  • Electric chillers shall be used in the baseline building design regardless of the cooling energy source, e.g., direct-fired absorption, absorption from purchased steam, or purchased chilled water.

  • The baseline building design's chiller plant shall be modeled with chillers having the number and type as indicated in Table G3.1.3.7 as a function of building peak cooling load.

Piping Losses

  • Piping losses shall not be modeled in either the proposed or baseline building designs for hot water, chilled water, or steam piping.

(Note: need to consider this as analogous to electrical system losses . The concept being that both piping losses and electrical distribution losses are small and difficult to standardize across the multitude of projects).

Chilled-Water Supply Temperature

  • Chilled-water design supply temperature shall be modeled at44°F and return water temperature at 56°F.

  • Chilled water supply temperature shall be reset based on outdoor dry-bulb temperature using the following schedule:

  • 44°F (6.7°C) at 80°F (27°C) and above

  • 54°F at 60°F (12°C at 16°C) and below

  • ramped linearly between 44°F and 54°F (6.7°C and 12°C)at temperatures between 80°F and 60°F (27°C and 16°C).

Chilled-Water Pumps

  • The baseline building design pump power shall be 22 W/gpm (349 kW/1000 L/s).

  • Chilled-water systems with a cooling capacity of 300 tons (1055 kW) or more shall be modeled as primary/secondary systems with variable-speed drives on the secondary pumping loop.

  • Chilled-water pumps in systems serving less than 300 tons (1055 kW) cooling capacity shall be modeled as a primary/secondary systems with secondary pump riding the pump curve.

Heat Rejection

  • The heat rejection device shall be an axial fan cooling tower with two-speed fans.

  • Condenser water design supply temperature shall be 85°F or 10°F (29°C or 5.6°C) approach to design wet-bulb temperature, whichever is lower, with a design temperature rise of 10°F(5.6°C).

  • The tower shall be controlled to maintain a 70°F (21°C) leaving water temperature where weather permits, floating up to leaving water temperature at design conditions.

  • The baseline building design condenser water pump power shall be 19 W/gpm(310 kW/1000 L/s). Each chiller shall be modeled with separate condenser water and chilled water pumps interlocked to operate with the associated chiller.

Computer Room Equipment Schedules

  • Computer room equipment schedules shall be modeled as a constant fraction of the peak design load per the following monthly schedule:

  • Month 1, 5, 9 - 25%

  • Month 2, 6, 10 - 50%

  • Month 3, 7, 11 - 75%

  • Month 4, 8, 12 - 100%

Supply Air Temperature and Fan Control

  • Minimum volume setpoint shall be 50% of the maximum design airflow rate, the minimum ventilation outdoor air flow rate, or the air flow rate required to comply with applicable codes or accreditation standards, whichever is larger.

  • Fan volume shall be reset from 100% air flow at 100% cooling load to minimum air flow at 50% cooling load.

  • Supply air temperature setpoint shall be reset from minimum supply air temperature at 50% cooling load and above to space temperature at 0% cooling load.

  • In heating mode supply air temperature shall be modulated to maintain space temperature and fan volume shall be fixed at the minimum air flow.

ASHRAE Building Labeling Pilot Program - Coming to a Data Center Near You?

ATLANTA – A new program to inform building owners and operators, tenants and prospective buyers on the energy use of buildings, similar to a nutrition label on food or miles per gallon ratings on cars, was launched today to encourage the building industry to find ways to cut energy use and costs.

The Building Energy Quotient program, which will be known as Building EQ, will include both As Designed (asset) and In Operation (as operated) ratings for all building types, except residential. It also will provide a detailed certificate with data on actual energy use, energy demand profiles, indoor air quality and other information that will enable building owners to evaluate and reduce their building’s energy use. The program is administered by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

 “Information on a building's energy use is the critical first step in making the necessary changes and choices to reduce energy use and costs,” Gordon Holness, ASHRAE president, said. “The Building EQ program provides an easily understood scale to convey a building’s energy use in comparison to similar buildings, occupancy types and climate zone, while also providing building owners with building-specific information that can be used to improve building energy performance.”

Holness noted that building energy use disclosure is already mandatory in California; Washington, D.C.; Austin, Texas; Washington State; the European Union; and Australia.

 Those participating in the pilot program are leading building owners and designers, real estate developers and government agencies, including:

·         The Durst Organization, the owner, manager and builder of 9 million square feet of mid-town Manhattan office and residential properties,  will include 4 Times Square, 1155 Avenue of the Americas and One Bryant Park in New York City in the pilot

·         The U.S. General Services Administration, the primary agency responsible for the acquisition and management of federal buildings owns or leases 8,600 properties and maintains an inventory of more than 354 million square feet of workspace for 1.1 million federal employees

·         Hines, a privately owned real estate firm involved in real estate investment, development and property management worldwide headquartered in London and Houston, Texas, will place high-profile properties from five major U.S. market in the pilot

·         The Detroit-Wayne Joint Building Authority will include the Coleman A. Young Municipal Center, which is home of six branches of city and county government including Circuit and Probate Courts, City and County Clerks and the Executive and Legislative branches of the City of Detroit, in the pilot

·         The Michigan Department of Management and Budget, which acquires and  manages properties for many of the state’s agencies       

 Through the pilot program, the Building EQ program will allow fine-tuning and final development of the program. In parallel with this effort, ASHRAE has developed a certification program for building energy modelers. Following completion of the pilot program in mid-June, the program is expected to be fully functional by the end of 2010.  Under the program, new buildings will be eligible to receive an As       Designed, or asset, rating, which provides an assessment of the building based on the components specified in the design and is based on the results of building energy modeling and simulation. An In Operation rating will be available once the building has at least one year of data on the actual ener gy use and is based on a combination of the structure of the building and how it is operated. Existing buildings would be eligible to receive both an As Designed and In Operation rating. “With procedures for both an As Designed and In Operation rating, building  owners can make side-by-side comparisons that could further reconcile differences between designed and measured energy use on an ongoing basis,”  Holness said.

LEED for Data Centers: Finally a Reality?


Many people have been inquiring on the status of the LEED for data centers standard that began as a project funded by the California Energy Commission and managed by Lawrence Berkeley National Labs. See for additional information on that effort.


Well the good news is that the US Green Building Council ( has embarked on a process that they call adaptation of the LEED standard 3.0. Simply put, under this process, credits are modified for a particular type of building that does not work well under the LEED standards due to the special nature of the occupancy, equipment, size, etc. This is a summary of the rules:


Credit Modification

  • Changes are proposed based on the current balloted credit language

  • The overall intent of credit cannot be altered

  • Only 6 modifications can be made (regardless of the number of rating systems being addressed)

  • 1 of the 6 modifications can be adoption of a “new” credit from another rating system

  • Entirely new concepts/credits to LEED are not permitted

  • No modifications are allowed to the minimum project and minimum eligibility requirements (though we will note issues for future deliberation/working groups)

  • Proposed modifications must be approved by LEED Steering Committee

  • Changing point values and weightings is not part of this effort

So we are working within the boundaries of the LEED standard for new construction, but are also looking to LEED for Commercial Interiors and LEED for Existing Buildings: Operations and Maintenance to determine the impacts and/or use credits from these standards that make sense for the New Construction standard.


We had our first meeting at the USGBC offices in Washington, DC last month. The team that is working on this effort is as follows:

  • USGBC: four representatives

  • Industry subject matter expert (liaison between working group and USGBC): Bill Kosik – HP

  • Working group: eleven representatives from consulting engineering firms, data center owners, builders, equipment vendors and researchers

The preliminary timeline is to have draft language to the USGBC’s technical and steering committees by late spring 2010. It is not clear yet when a final standard would be made available and/or when pilot projects will be requested.




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  • I’m a Global Strategist, a certified (PMI) Project Manager, specializing in business to IT alignment, agility consulting, Infrastructure Transformation and Strategic Architecture for Big Data, Mobility, Private Cloud, Unified Communications and Collaboration. I drive the strategy, vision and content of strategic consulting services in the Big Data IT Infrastructure services area at HP. As part of this, I meet with senior level customers to understand their challenges, conduct workshops to determine future vision and roadmaps as well as presenting at industry and analyst events.
  • Craig Partridge is the WW strategy lead for HP Technology Services Networking group. His role now covers strategy for consulting, professional and support services. The major areas of focus are Mobility, UC, Cloud Networking and IPv6. All aligned to core HP networking solutions - simplified, secure, optimized and available.
  • Don has held roles with the business and marketing of consulting for HP. Currently he supports HP's Client and Microsoft Solutions and the emerging Mobility Consulting services. He holds a MBA from UCLA's Anderson School.
  • Over 12 years of consulting, new technology services development and marketing experience covering data center, IT infrastructure, cloud technology domains. Hande holds a M.B.A degree from Bentley College, MA.
  • Having joined HP in 2003 Ian Jagger is the world-wide marketing and program manager for HP Technology Consulting's Strategic Consulting Services, Critical Facilities Services and Energy and Sustainability Management Services, as well as emerging IT services Prior to his current role, he served as the HP Services Marketing Manager for Central and Eastern Europe, Middle East and Africa, having joined HP in a similar role in the Middle East. Prior to HP Jagger had a 15 year international sales career, culminating in being Sales and Marketing Director for Steelcase Inc addressing Northern Europe before focusing more specifically on marketing. His initial focus was consultancy and interim marketing management, primarily for small to mid-sized customers based or looking to expand in the Middle Eastern region. Immediately prior to joining HP he was a strategic marketing consultant addressing investment targets for a technology fund. Born in Rochdale, United Kingdom, Jagger holds an honors bachelor of science degree in economics and a degree in social psychology from Loughborough University, England. He also holds a Masters Diploma in Marketing from the Chartered Institute of Marketing, is a Member of the Chartered Institute of Marketing and a Chartered Marketer. He has one daughter and lives in Cary, North Carolina.
  • Jeff Enters works in the HP Technology Services Networking organization and consults with customers on their IT strategies. He has over 20 years of consulting, design and integration experience in multi-vendor Voice and Data environments.
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  • Editor and writer with 12+ years experience in the corporate software and technology sectors.
  • Jordan owns the strategic direction and evangelism of HP’s mobility and digital workplace services portfolio. He engages with customers around the world to discuss the tremendous potential of mobility for building more responsive, more nimble businesses and agencies by redefining end user productivity and innovation with IT solutions for the New Style of Business
  • Ken Larson has over 30 years of experience in Information Technology aligning business to technology. As an Enterprise Architect, he has delivered many successful architecture related services across business and government sectors in manufacturing, insurance, banking, oil, utilities, US state and federal governments. He is certified in TOGAF and IT Service Management.
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  • Working for EMEA TS Consulting, I am a Specialist in end to end management of customer data, from creation through consumption, to protection and preservation and ultimately (controlled) destruction. This includes, host, connectivity, storage, data protection and backup and archive, from a technical and more importantly, operational perspective. I have worked in the storage and data management industry for over 15 years, on both sides of the desk, as a customer and now as a consultant.
  • Patrick Lownds is a Senior Technology Consultant and is involved in designing and delivering both Client Virtualization and Cloud Computing solutions in the datacenter. Patrick co-authored “Mastering Hyper-V Deployment
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  • Tim Swiader has twenty plus years in the Information Technology industry. He has worked primarily with the fortune 100 and legacy carriers transforming their applications, networks and data center facilities.
  • Tari is a Distinguished Technologist with 30 years of IT and cyber security experience. He is dual board certified in information security/business continuity and is responsible for a wide range of management and technology consulting services encompassing information security, disaster recovery, privacy, and risk management. His problem-solving skills, knowledge of various technology platforms, compliance statutes, industries, as well as his experience in deploying defense-in-depth and InfoSec Program solution architectures is commonly applied when advising CIOs/CISOs as well as leveraged in numerous HP client engagements throughout the world. Tari has designed, built, and managed some of the world’s largest InfoSec programs allowing them to defend against even the most aggressive attackers.
  • I provide technical consulting services at all phases including analysis, planning, design and implementation. I have a wide range of experience in WAN and LAN technologies, as well as providing security solutions and deploying operating system infrastructure. Besides working directly with clients to deploy technology in their data centers, I also find myself architecting or discussing solutions with a business’s chief information officer, helping to lay out a roadmap for the coming years.
  • Bill Kosik, PE, CEM, BEMP, LEED AP BD+C, is a Distinguished Technologist at HP Data Center Facilities Consulting (DCFC). He is responsible for execution of project work, training and mentoring of internal engineering and consulting teams, research and analysis of topics related to data center energy use, and industry presentations and writing assignments. He is one of the main technical contributors who have shaped the DCFC technical expertise in energy use optimization and sustainable design practices in data centers. He is a member of the Consulting-Specifying Engineer Editorial Advisory Board.
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