ASHRAE 90.1— 2007 and beyond

Engineers talk about the present and future standard for energy efficiency.

By Patrick Lynch, Associate Editor, and Michael Ivanovich, Editor-in-Chief March 16, 2010

CSE: What areas—building systems, energy performance, efficient technology—does the new version of ASHRAE 90.1-2010 focus on that was not addressed by previous versions of the standard?

Mick Schwedler : Since ASHRAE/IES 90.1 covers the entire building, all aspects are being addressed by addenda to the standard. This includes the building envelope, lighting power densities, power, equipment efficiencies, and HVAC and service water heating system requirements. In addition, there has been substantial work on control of lighting, daylighting, and HVAC systems. The Energy Compliance Budget (ECB) and Appendix G (used for LEED) modeling requirements have also been updated.

Michael Tillou : The things in the 2010 version of the standard that I am excited about are new regulations for data center energy efficiency, specific air barrier requirements, and the move away from treating ventilation as energy neutral in recognition of the fact that good ventilation system design not only improves IAQ, but increases building energy efficiency.

Jason Gerke : The proposed updates to ASHRAE 90.1 include a requirement for commissioning of lighting control systems by a person not involved in the design or construction of the project. Experience as a commissioning agent on various new buildings, along with retro-commissioning activities in existing buildings, has shown me that lighting controls are often left to the installing contractor for verification. Lighting controls are rarely programmed correctly to match building occupancy schedules, and the calibration of daylight sensors must be checked prior to project completion. ASHRAE 90.1 requires that automatic lighting controls are provided in buildings so it should be expected that operation of these control devices and programs are verified to operate according to the requirements of the design team.

Peter McDonnell : The standard has really continued to evolve since the 1999/2001 edition. The latest addendums (effective Jan. 1, 2010) have further defined equipment efficiencies by setting specific values or defining the parameter that manufacturers use to rate the efficiency (for example, Addendum S for heat pumps). I would have to say that current edition of the standard has continued to push in all three areas listed.

CSE: How does ASHRAE 90.1-2010 factor regional climate differences into a building’s energy performance? In future versions of the standard, what climate considerations need to be included when evaluating how a building performs?

Tillou : The 2010 version of the standard uses climatic zones to prescribe building envelope requirements, and some HVAC requirements like air-side economizers and energy recovery. Looking into the future, I think climatic considerations need to be factored into the selection of baseline system types in the Appendix G Building Performance Rating methodology. For example, buildings with heat pump systems in cold climates currently get to claim a significant improvement in energy performance because Appendix G stipulates a baseline that uses electric resistance reheat coils.

Schwedler : The standard defines eight climate zones. They range from Climate Zone 1 (hot) to Climate Zone 8 (arctic). Building envelope requirements are defined for each of the climate zones. In addition, three major climate types are defined: moist (designated as A), dry (B), and marine (C). Marine climates include portions of the United States’ West Coast.

A number of HVAC requirements differ depending on the climate type. For example:

  • Chicago is in Climate Zone 5A (moist). Presently the minimum system size for which an economizer is required is 135,000 Btu/h.

  • Las Vegas is in Climate Zone 5B (dry). Presently the minimum system size for which an economizer is required is 65,000 Btu/h.

CSE: There have been some rumblings about the advantages air systems have over hydronic systems within 90.1. What’s your perspective on this issue?

Gerke : System selections are always application specific, and Standard 90.1 should not compel design teams to choose between an air- or water-based systems for a project based on perceived efficiency requirements. The design team should always be given the opportunity to select the most efficient system for the project at hand and not have to select an air or water system based on adopted code bias for specific building types. Standard 90.1 should not dictate a system type and then penalize the design team for not following the requirements set forth by a committee.

Schwedler : The Standing Standard Project Committee (SSPC) uses the same economic criteria to guide its professional judgment—no matter the system type. If people have questions or concerns about portions of the standard, ASHRAE processes allow anybody to submit a Continuous Maintenance Proposal. This offers the opportunity for people to submit specific changes they feel would address the issue, and the committee must respond. As I’ve told people in every 90.1 presentation I’ve given, we’re very interested in changes that practitioners feel would help the standard be clearer, more enforceable, and more efficient.

McDonnell : A consensus standard such as 90.1 will keep a balance between the system types, so long as the voting membership also represents a balance. Historically, 90.1 committee’s leadership has worked hard to be well balanced, which remains a very difficult task to achieve.

Tillou : The intent of the standard is to set minimum efficiency requirements for systems that are included in a proposed design, so I don’t think air- or water-side systems are favored in any way.

Interestingly, I was on a panel discussing Standard 90.1 at the 2008 Northeast Sustainable Energy Assn . conference and this very question came up. In that case, it turned out to be a lack of understanding about how to apply the standard. The concern arose because an extremely innovative design using natural ventilation and hydronic heating was flagged by a local code official for not meeting certain mandatory requirements for air-side systems. What the code official had not realized was that the requirements were not applicable because the design did not include any air-side systems.

CSE: As ASHRAE continues to make 90.1 broader, deeper, and stricter, how might it be overly limiting engineers and architects from presenting creative solutions?

Tillou : I do not accept the notion that changes to the standard limit the creativity of engineers and architects. By improving Standard 90.1, ASHRAE has changed the definition of “standard engineering practice” and raised the bar of building system design by discouraging inefficient engineering practices. As engineers, we can no longer rely on “rules-of-thumb” and design practices passed down by previous generations of engineers as acceptable solutions to the current challenge of designing energy-efficient buildings.

Schwedler : The committee makes it a top priority to keep options available to design teams. As the world focuses on energy reduction, the requirements of the prescriptive path become more stringent. Sometimes the committee allows multiple paths within the prescriptive section. In addition, the energy cost budget (ECB) method path is always available to project teams. It’s important to understand that even in modeling there are mandatory requirements, such as equipment efficiencies, that may not be traded off. This path allows for extreme creativity.

Gerke : ASHRAE 90.1 provides three compliance methods for the building design team to follow. The ECB method allows the designers to prove compliance of nonstandard designs and systems using new or unique materials. The standard will continue to allow design teams to be creative as long as the ECB method remains a compliance path option.

McDonnell : The standard has provided an alternative method to calculate compliance that can always be used. The mandatory provisions could be considered limiting; however, these have resulted in pushing design teams to follow better design practices and the equipment manufacturers to increase their efficiencies to remain competitive.

In the end, I believe that the standard actually gives architects and engineers better opportunities to be creative while being energy responsible. As the standard continues to move forward, the opportunity to use alternative methods for compliance must (and will) be maintained. People need to recognize that the prescriptive method is just one way to achieve compliance. It is important to also consider that the prescriptive method is intended to be a guide.

CSE: With 90.1 being both complex and continually evolving, what can be said about the ability to enforce it in the field?

McDonnell : The reality is that adoption and enforcement of 90.1 are at the state or local level. I have worked with building departments that require a standardized energy code calculation be submitted in order to obtain a building permit and others that do not have any requirement for submission. Additionally, there are states that are very proactive in adopting energy codes quickly and others that do not have a state energy code. The standard and the U.S. Dept. of Energy (DOE) have also provided forms to show compliance.

The main point is that the adoption of an edition of 90.1 is only the first step in the process. Education of the building officials and construction community (architects, engineers, owners, and contractors) in that jurisdiction then must continue the process for it to be successful. Standard 90.1 will evolve at a faster rate than adoption, and folks just need to understand this.

Schwedler : First, there are code officials and former code officials on the committee, so enforceability is often discussed as proposals are considered. In addition, a number of SSPC members have had the privilege to speak at the energy codes meetings sponsored by the DOE. Education of building practitioners and code officials is imperative if we are really going to save energy. I love it when there are code officials in the audience during 90.1 presentations, because then the design and code communities have the same understanding of the standard’s requirements and discuss any issues.

Gerke : ASHRAE 90.1 is written in code language, which allows governing authorities to adopt it as their energy code. The standard is also written in a format similar to existing energy codes allowing individual sections to be adopted, amended, or references removed. The standard allows governing authorities to pick and choose which sections to apply depending on local conditions and governing body energy goals.

Tillou : There is no doubt that enforcing the requirements of the standard is a challenge. In my experience many code officials just do not have the time to perform anything more than a cursory review of energy performance, especially when there are more important life safety concerns that must take precedence. Ironically, the U.S. Green Building Council (USGBC) has become the de facto energy code authority on many building projects throughout the country as they continually strengthen their review of the energy performance credits for the LEED rating system. However, although I am encouraged that the recent American Recovery and Reinvestment Act legislation requires states to improve energy code enforcement, I know the reality is that without significant funding and oversight, the necessary improvements will happen much more slowly than they need to.

CSE: How are 90.1, 189.1, and the International Energy Conservation Code (IECC) related?

McDonnell : Standard 90.1 is an American National Standards Institute standard and therefore transcends the ASHRAE and Illuminating Engineering Society (IES) organizations that participate in the formation of this standard. The International Conference on Climate Change (ICCC) 2009 Chapter 5 (Commercial Energy Code) allows you to comply with ASHRAE 90.1-2007 as an equivalent to the balance of the chapter. Overall, 90.1 is the default basis of these and other codes and standards such as LEED and NFPA.

Schwedler : Chapter 5 (Commercial Energy Efficiency) of IECC 2009 states, “…commercial buildings shall meet either the requirements of ASHRAE/IESNA Standard 90.1 … or the requirements in this chapter.” Standard 90.1-2007 is referenced. The rest of Chapter 5 defines requirements that must be met if 90.1 is not the chosen path. Many of the requirements are similar, but not identical, to those in 90.1. It’s also noted that NFPA references 90.1-2007 directly, and some local and state codes directly reference versions of 90.1.

Tillou : Standard 90.1 and the IECC both regulate building energy efficiency and are similar in terms of the stringency of their regulations. Standard 189.1 regulates all aspects of a sustainable building, not just energy efficiency.

CSE: How are LEED rating systems and 90.1 related?

Tillou : LEED rating systems reference ASHRAE Standard 90.1 as the baseline for determining the energy performance of buildings. In the latest version of LEED New Construction (NC), a building must comply with the mandatory requirements of the standard and demonstrate a 10% improvement in annual energy performance. Using the Building Performance Rating Method in Appendix G of ASHRAE Standard 90.1, a user creates a typical baseline building design that minimally complies with the standard as a basis of comparison for the proposed building design.

Gerke : The LEED rating system and ASHRAE 90.1 have a number of similarities. These similarities include both ASHRAE Standard 90.1 and LEED requirements for design teams to plan new buildings or upgrade existing facilities with the most energy-efficient equipment available and minimize building energy use. This applies to energy-consuming systems in the building including HVAC systems, service water heating, and lighting. The LEED rating system also uses Standard 90.1, Appendix G as a compliance path in the Energy and Atmosphere credits. Proposed buildings may be modeled using the Performance Rating Method. This interaction between these programs indicates how each entity has an end goal of energy reduction.

Schweder : The answer varies depending on the vintage and version of LEED. Assuming NC or major renovation LEED certification is being sought, LEED NC v2.2 requires that buildings have 14% lower energy cost than a building as defined by 90.1-2004. LEED NC 2009 requires the energy cost to be 10% lower energy cost than a building as defined by 90.1-2007.

The LEED documents refer to Appendix G of the respective 90.1 standards to define project modeling requirements. The ECB Subcommittee of 90.1 works closely with the USGBC Energy & Atmosphere Technical Advisory Group (EA TAG) to address energy modeling issues. At least four members of the 90.1 committee have served on the EA TAG, so there is good communication between the groups.

CSE: Do you think ASHRAE 90.1 should be expanded to cover industrial processes? Why or why not?

Tillou : This is a great question that has raised a lot of debate. Obviously, Standard 90.1 has no place regulating industrial processes or equipment necessary for the success of American business and industry. However, the purpose and scope of the standard does need to be expanded to address the opportunities to improve the energy efficiency of process systems and equipment that can and should be regulated.

Data centers are a great example of buildings with process cooling systems that are currently exempt (from ASHRAE 90.1) but shouldn’t be. Because the primary purpose of the air conditioning systems in data centers is for something other than providing human comfort, they are not required to meet any minimum efficiency criteria. However, these systems typically use commercially available equipment that is currently regulated by Standard 90.1 so there is really no good reason for their exemption.

In my opinion, the standard committee has done a good job crafting a new title, purpose, and scope for Standard 90.1 that strikes a balance between allowing the regulation of process equipment efficiencies and exempting equipment not specifically regulated by the standard. As with any regulation, there is always the potential for abuse, but I think it would be extremely difficult for ASHRAE to begin regulating process and industrial systems that have no place in Standard 90.1.

Schwedler : Presently, equipment and portions of building systems that use energy primarily for industrial processes are outside the scope of 90.1. There are no plans to add industrial processes. Why is this? My brother is in the printing business; today we do not have expertise to define requirements for a printing press. It is possible that at some time in the future, industrial processes will be brought into the scope of the standard. If so, the SSPC will continue to work with the ASHRAE Technical Committees covering industrial processes, as well as industrial stakeholders.

Gerke : The ASHRAE 90.1 Standard has a number of components that could currently be used when designing and specifying industrial process systems. The standard covers minimum equipment efficiencies, lighting and temperature controls for building areas, and requirements for service water heating. Design teams presently may use the standard for reference when specifying process system components and materials. It may be impractical for ASHRAE 90.1 to attempt to provide minimum efficiency goals for industrial processes due to the diversity of process applications.

McDonnell : I do not believe that industrial processes should be included in the 90.1 standard. First, this could have a negative impact on our economy in the long term. Second, the fact is that companies will find ways to reduce energy consumption in their industrial processes to reduce costs and increase profits. The industrial market will lag behind the commercial and institutional markets in terms of energy conservation, but it has also been at the forefront on pollution reduction (rightly so). As the cost of energy continues to rise, the industrial market will increase its efforts in conservation.



Jason R. Gerke , PE, LEED AP

Associate, GRAEF, Milwaukee

Peter W. McDonnell , PE, LEED AP

Senior Mechanical Engineer, McClure Engineering Assocs., St. Louis

Mick Schwedler , PE, LEED AP

Chair, ASHRAE/IES 90.1 (responding as an individual) Manager Applications Engineering, Trane, La Crosse, Wis.

Michael Tillou , PE, LEED AP

Associate Vice President, Director of Energy Services, Cannon Design, Grand Island, N.Y.