Best Practice Guide

Commercial Office Buildings

Planning an Energy Program

Assessing Energy Performance

Sunset Sierra Properties, an ENERGY STAR building. Photo courtesy of Transwestern Commercial Services.View Details.

The best way to assess how well a building performs in terms of energy management is to track the energy profile over time, establish baseline data, and then compare the performance results against other, similar properties.

Without establishing a baseline for energy performance, facility managers have no way to know a building's potential for saving resources, both financial and natural. This is similar to timing a runner. Without a stopwatch, we only know that the runner runs, not that she runs fast, or that she runs faster today than yesterday. Comparing energy use against an established baseline does the same thing for energy management that a stopwatch does for the runner.

There are two primary ways to establish baseline data:

  1. Use an energy accounting system to analyze historical energy use, carefully taking into account any changes in operations, extreme seasonal weather or other factors that might affect the energy use intensity or energy costs at a building or property.
  2. Model energy use in the building, also referred to as calibrated simulation. This involves the use of complex computer software to predict energy use in a building.

Often, energy efficiency and energy conservation measures are adopted to address discernible problems, such as uncomfortable indoor temperatures or wide fluctuations in utility bills. An energy accounting system that tracks the energy performance of a building and compares this to baseline data can help detect and confirm such problems, including malfunctioning cooling equipment that appears as a spike in energy demand of the heating, ventilating, and air conditioning (HVAC) system.

Modeling a building's predicted energy use goes a step further identifying buildings with suboptimal performance that may not have discernible problems. A building with an oversized HVAC system running at full capacity, for example, will provide adequate climate control, but may consume as much as 50 percent more energy than is necessary to do the job. Modeling can predict which subsystems should be downsized without compromising air quality or comfort.

In addition to analyzing energy performance against a baseline, owners and managers can use benchmarking to compare a building with properties of similar characteristics, such as climate, size, operations and age. This comparison demonstrates whether a building's energy performance is in line with expectations. A new facility developed following California's stringent building codes, for example, should expect to perform as well as, if not better than, older buildings of similar size and operations. A low ranking in this case might alert building staff to conduct an energy audit that would identify areas for improvement. A high ranking, on the other hand, would demonstrate that the building is truly energy efficient and could be marketed as a best-in-class property.

Tracking Historical Energy Use to Establish Baseline Data
The easiest way to establish baseline data is to make a statistical comparison of historical energy performance. Depending on the scope of the existing energy accounting system, much of this information may already be in hand. Useful data streams and sources might include:

  • Total demand, peak demand and energy cost - available from the local utility.
  • Degree-day data - available from online sources like the National Climate Data Center.
  • Building occupancy - available from building or company management, such as the human resources department or leasing office.
  • Building operations - available from building staff and tenants.

When setting up an energy management system or energy accounting system, it is important to collect the right data. These systems can literally track hundreds of individual data points, quickly overwhelming the end user with too much information. To narrow and better target the information collected, adapt the energy goals and objectives expressed in the energy policy into key performance indicators. These indicators will then determine which data points are most useful to collect - data should be aligned with and consistent to the key performance indicators. This winnowing process reduces the number of superfluous data streams, making the information gathered easier to analyze and manage.

Advanced meters and submeters further facilitate data collection. In addition to providing real-time information about onsite energy demand and the related costs, advanced meters and submeters may also detect operational inefficiencies, equipment in need of repair, and billing errors. For more information, see Operations and Maintenance.

A number of outside sources can help establish both expectations and methodology for establishing baseline performance. Title-24 (California's Energy Efficiency Standards for Non-Residential Buildings) and the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) 90.1 Energy Standard for Buildings, for example, both provide information on the minimum performance levels a new building should attain in terms of energy efficiency. Businesses can adopt and adjust these standards to set their own goals and objectives.

Example: lighting systems should beat Title-24 efficiency standards by 10 percent.

The International Performance and Measurement Verification Protocol (IPMVP) is particularly useful because it describes concrete steps for establishing baseline data. Similarly, ISO 14001, an internationally used standard for developing an environmental management system, includes guidelines for establishing an energy baseline and tracking energy performance. Businesses and organizations that adhere to management quality methodologies, such as Six Sigma and ISO 9000, should find that these programs, too, are consistent with and offer tips for performance tracking.

Modeling Energy Use to Predict Energy Use and Establish Baseline Data
Sophisticated software programs allow users to model, or simulate, a building's energy performance. Often done when there is an absence of usable historical or post-retrofit data - or when it is difficult to isolate individual energy efficiency or energy conservation methods - modeling can estimate how much energy is being used and make predictions about future energy use and costs. Modeling can also be used to predict which energy efficiency or energy conservation measures will be the most cost-effective - all while pointing out potential tradeoffs between options. .

Modeling is a complicated process that requires training and experience to administer properly. Software must be carefully selected and set-up to ensure that it has the capabilities needed to correctly model a building's specific features. Inputs into the computer simulation must be as accurate as possible, and may take considerable time and resources to collect and verify. Similarly, software must be carefully "calibrated" to ensure that predictions reasonably resemble actual conditions. Results must then be assessed and shown to be reasonably accurate -- often anomalies arise that require further investigation.

As modeling is expensive and timely, local governments taking this track should be prepared to invest time and money to ensure that the program generates the desired results. It is not unusual to have 8760 hours of trend logging, for example, as part of the energy modeling - that's 24-hours a day, 7-days a week, 365-days per year. Using an energy accounting system and benchmarking performance are both quicker and less costly ways to assess a building's energy performance.

Benchmarking to Compare Performance
Benchmarking allows owners and managers to compare a building's energy use intensity (EUI) against buildings of comparable operations, size, and climatic region. EUI is generally expressed as the annual average kilo-British thermal units and kilowatt-hours per square foot (kBtu/sq. ft. and kWh/sq. ft.), or as the total annual energy cost per year per square foot ($/sq. ft.). Although benchmarking cannot identify potential energy savings, it might suggest when energy demand or costs are out of line.

One valuable benchmarking resource is the Commercial Building Energy Consumption Survey (CBECS), a quadrennial sample survey that collects data on energy-related building characteristics, energy consumption, and expenditures for commercial buildings in the United States.

Another resource, based on CBECS, is ENERGY STAR's Portfolio Manager, an online tool that ranks buildings on a scale of 1 to 100. Buildings with a score of 75 or greater achieve an ENERGY STAR label. Portfolio Manager can also continuously track and manage energy data, helping to simplify record keeping. Nationally, about 19,000 buildings have used Portfolio Manager, including 17 percent of all office buildings in the United States.

Besides Portfolio Manager, a number of other benchmarking tools, software applications, and services are available. For example, CalArch, developed by Lawrence Berkeley National Laboratory in partnership with the California Energy Commission Public Interest Energy Research (PIER) Building Energy Efficiency Program, compares California buildings of similar characteristics; it is accessible online and is quick and easy to use. The International Facility Management Association (IFMA) and the Building Owners and Managers Association (BOMA) are additional sources of information. Both associations conduct periodic surveys that compile useful information about member responsibilities and facility performance.

If benchmarking data suggests that a facility does not perform as well as it could, conducting an energy audit will identify areas of potential improvement. See the following section for more information.

ENERGY STAR Benchmarking

ENERGY STAR Benchmarking
To use ENERGY STAR Portfolio Manager, buildings must have at least 50 percent of the total floor space occupied by at least one of the following: office (general, bank branch, financial center, or courthouse), hospital, medical offices, hotel/motel, K-12 school, supermarket or grocery store, dormitory or residence hall, or warehouses.

Green Building Initiative

Green Building Initiative
Governor Schwarzenegger's Executive Order S-20-04, commonly referred to as the Green Building Initiative, directs the California Energy Commission to develop a plan to implement a State benchmarking program for all commercial buildings. The intent is to clarify which buildings are energy efficient, making benchmarking information available to potential tenants, buyers, and lenders. The proposed program will be coordinated with the U.S. EPA's ENERGY STAR benchmarking tool, Portfolio Manager.

Business Examples

Glenborough Realty Trust uses the ENERGY STAR commercial building program to benchmark properties across the country. This helps identify which buildings could benefit most from energy upgrades, allowing Glenborough to invest in the highest return projects. Servidyne Systems, Inc., an engineering services and software company, tailors ENERGY STAR tools to fit Glenborough's needs. So far, Servidyne and Glenborough have worked together to earn 11 ENERGY STAR labels in the first year since initiating an energy management program.

Transwestern Commercial Services adopted ENERGY STAR's benchmarking program to reduce property operating costs as well as carbon dioxide emissions. As a property management company that recognizes the importance of maintaining and improving asset value, Transwestern undertakes this commitment on behalf of the properties' actual owners. Transwestern expects to have 100 percent of its property portfolio benchmarked by mid-year 2005, and has made energy efficiency upgrades at 200 individual locations.

Equity Office Properties models energy usage in buildings with a computer-based monitoring system. This allows engineers to evaluate each building from 'top to bottom,' and map out various investment scenarios. These scenarios are then analyzed to determine possible financial benefits from building performance enhancements. Equity Office can also use modeling to identify possible changes in operations or procurement processes that would improve energy efficiency.

As a standard practice to help evaluate energy performance, Cushman & Wakefield routinely benchmark all facilities under its management. At Adobe Towers in San Jose, this goes one step further - the results of annual ENERGY STAR benchmarking are tied to Cushman & Wakefield's management fees. As a result, the East Tower was labeled in 2003 and 2004, and the West Tower was labeled in 2004.

Adobe also participates in the annual Building Owners and Managers Association "Experience Exchange Report," and the International Facility Management Association "Annual Benchmarking Report."


Resources

U.S. Department of Energy, Energy Information Administration, (CBECS).

U.S. Environmental Protection Agency (EPA), ENERGY STAR, Portfolio Manager.

U.S. EPA, ENERGY STAR, Energy Management Assessment Matrix.

Lawrence Berkeley National Laboratory and California Energy Commission Public Interest Energy Research program, California Building Energy Reference Tool, CalArch.