Sustainability In Commercial Buildings — Bridging The Gap From Design To Operations
By: Michael Bobker, Adam Hinge, Om Taneja
May 02, 2008
The green, high performance buildings industry has seen exponential growth in recent years. A plethora of new technologies and practices have rapidly evolved with the intent of reducing buildings’ impacts on the environment and improve the indoor air quality and worker productivity. An overwhelming amount of information is flooding the buildings trade literature with claims about improved performance.
Unfortunately, most of this information is based on expected performance, instead of actual measured or demonstrated performance. While initial concepts and design documents express a modeled performance, too often that is not effectively translated into commensurate operations, maintenance, refurbishment or user awareness and acceptance.
How much variance there is between expected performance and actual, measured performance during occupancy/operation is not completely clear. One of the more comprehensive studies looking at 121 buildings certified through the US Green Building Council's "Leadership in Energy & Environmental Design (USGBC's LEED) program found that, on average, LEED buildings are 25-30% more energy efficient than non-LEED buildings (NBI 2008). It also found that in these 121 buildings, 30% perform better than expected, about 25% perform worse than expected, and a handful of buildings have serious energy consumption problems.
These findings are encouraging, though a major caveat to the report and data is that it only reports on a self-selected 121 buildings out of 552 LEED certified buildings; it is unclear whether this portion of the buildings are representative of the broader set of certified buildings, or not. Anecdotal information suggests that a much higher percentage of buildings are operating at significantly higher energy use than predicted — much more study is needed to understand the true performance gap.
A recent study reported by World Resources Institute indicated that for buildings in New Zealand, during the life-cycle, only 10% of energy is used during initial construction, and remaining one third each is used during operations, maintenance/refurbishment and transportation (Camilleri & Jaques 2001). Therefore, how well we transition from design/construction to occupancy, and then operations and maintenance, makes the most significant impact on environmental performance. There is a tremendous need for more information on "lessons learned," where practitioners can explain what worked: what went right, what didn't work so well, and what they might do differently if given the chance (Learning from Our Buildings 2001) Having the operating and maintenance ("O&M") managers participate in design, and timely and ongoing training of O&M Staff, can obviate some of the hurdles that adversely impact the performance. Increasing the feedback from building operators to the design and construction community is critical.
Managing Expectations and Getting to Better Predictions
The road to high-performing buildings is paved with high expectations — but, ultimately, it is measured performance that shows how energy efficient a building really is. All too often a building's energy performance does not meet design expectations, particularly expectations set by a new building's energy savings projection that may overstate achievable performance. Across the high-performing building industry, unrealistic energy performance goals have come from such things as:
- inadequate modeling practices
- unreliable controls and control systems and inadequate monitoring
- significant changes in space usage and processes during occupancy and tenant improvements,
- failure to include operations staff in goal setting or accurately communicate the design intent to the staff, and
- lack of adequate budgets for commissioning, evaluation and ongoing benchmarking.
In any rapidly growing industry, performance expectations are reported at a rate that outpaces publication of actual results. Therefore designers' base of knowledge is limited. Poor feedback of results further hinders the accuracy of design projections. In the case of green buildings and their actual operating performance, potential savings seem to be often over-stated. Some of this may be due to a lack of precision about what is being measured and expressed.
In one recent example, the new Seattle City Hall, which received a U.S. Green Building Council (USGBC) LEED(R) Gold rating in 2003, became front-page news in the Seattle Post-Intelligencer "Seattle's New City Hall is an Energy Hog: Higher Utility Bills Take the Glow Off Its 'Green' Designation", July 5, 2005. The new city hall does use more energy than the old city hall, for a variety of valid reasons including much greater ventilation levels, different uses between the two buildings, and vacancy levels in the old city hall. But this press coverage clearly indicates the need to better manage expectations to avoid damaging news stories. This type of out-of-context information can erode confidence in the industry and discourage other owners and managers of high-profile high-performing buildings from releasing actual energy performance data.
As more actual energy performance data on high-performing buildings becomes available, clearer and more realistic expectations will help to establish confidence within the building design and construction industry about costs and savings. Especially because energy cost savings are often cited as offsetting additional first costs of green buildings, it is important to narrow the gap between the predicted energy benefits and actual measured, savings. Accurate reporting of the actual performance of green buildings is important will help the industry to calibrate its expectations and move towards more consistent results and confidence in projections. Sharing operating results and lessons learned earlier rather than later can avoid repeating potential mistakes as the green buildings movement proceeds.
What do we know About Sources of Under-Performance?
Operations — Tenant Use
Tenants are not always made aware of how their use of spaces and equipment affect the energy use and environment. Tenants use ancillary equipment, such as heaters, fans and task lights, if proper air flow and services are not effectively delivered. Without their active participation and commitments, some of their actions inadvertently negate the benefits of high performance design elements. Encouraging tenants not to use space heaters and fans, and to turn off equipment during off hours, making sure to shutting off lights, power down everything — such as computers, monitors, copiers, kitchen equipment and task lights, can significantly reduce plug loads. In U.S. companies alone, more than $1 billion a year is wasted on electricity for computer monitors that are left on when they shouldn't be.
Cleaning and security personnel can be trained to turn off miscellaneous items such as coffee pots, kitchen equipment and individual office lights. Office equipment that is left in stand-by mode continues to draw significant power on a 24X7 basis and degrades the energy performance. It is important to adjust building operating hours, and the provision of heating and air-conditioning levels, to reflect actual tenant usage and needs.
Operations — Systems and Operators
Many high performance buildings are designed with state of the art efficient and complex equipment, particularly controls, which can be very difficult to operate optimally. While these systems may be the best from a design perspective, the realities of commercial operation are often not adequately considered in establishing design intent that is realistic and achievable. Complex building systems (in any building, not just green or high performance buildings) often require improvements and iterative adjustments over multiple seasons to ultimately operate as designed. Complicating this situation is the fact that design intent is not well communicated to operators and rarely if ever in a quantified manner that can be readily checked against accessible building data.
For example, discharge air temperature sensors are often found to be reading several degrees higher than the actual temperature. This results in significant excess cooling plant energy use. Generally, only a small sample of sensing elements is validated, leading to inaccurate control. Further, in actual practice, many control loops are unstable as installed. Careful testing and monitoring of system performance under actual load is essential to identify and correct instabilities inherent in the systems as installed. Most complex buildings can easily take three years (or three seasonal cycles) to be brought up to optimal operation. Unfortunately clients are hesitant to pay designers to return after occupancy, and designers have generally moved on to the next urgent project deadline.
Another element that can result in low building performance is a disconnect between design and operation--at the time of design and modeling predicted energy performance, optimal control strategies and schedules often are assumed which do not occur in operation. For example, daylighting strategies would normally assume that artificial lighting is dimmed or turned off but operators or occupants often do not understand this and may well not recognize if the controls are not working properly. Lack of commissioning can result in systems that are not operating as designed, frustrating operators and occupants. Improper function that results in unacceptable indoor environment conditions will often result in by-passed control routines. To manage expectations for energy performance, the design team must consider operational needs, situations, and responses from the beginning of the project.
Modeling can be one major issue in understanding why energy expectations are not being met. Potential inaccuracies of energy modeling are well known, nonetheless common errors persist. Most energy modeling tools are very good at modeling standard HVAC systems, but it can be more of a challenge for less experienced modelers to predict the energy use of advanced green building components such as natural ventilation, atria, displacement ventilation, chilled beams, and double facades, among others.
As noted above, with sophisticated systems and new technologies, actual energy performance is often quite different from predicted performance, particularly for the first years of operation. The issue of predicted energy performance differing from actual is not unique to green buildings; the challenges of accurately modeling and predicting building energy use apply to all buildings, though the same scrutiny about performance is usually not applied to the general building stock.
What's in the Metrics
Many earlier energy codes and rating schemes did not take "process energy" (sometimes called "unregulated energy") into consideration, defined in ANSI/ASHRAE/IESNA Standard 90.1-1999, Energy Standard for Buildings Except Low-Rise Residential Buildings, as "energy consumed in support of a manufacturing, industrial, or commercial process other than conditioning spaces and maintaining comfort and amenities for the occupants of a building."
As an example, many design teams will gather energy performance data for energy-efficient buildings, and make performance predictions, by comparing only the systems that the design team controls — such as envelope insulation value, percentage glazing, solar shading, chiller and boiler efficiency, fan and pump motor efficiency, installed lighting power density, and system selections. This excludes the "process energy" elements, often some of the biggest end users in new buildings, such as server rooms, lab equipment, cooking or restaurant equipment, security systems, building control systems, fire safety systems, computers, printers, copiers and some plug loads.
Many of these excluded loads operate 24 hours a day, seven days a week; while an energy savings calculation will state significant energy savings, the real energy use of a new building may be much higher. These details need to be considered when setting goals and reporting both projected and actual energy performance.
Keeping Score: Getting to an Appropriate Set of Metrics
Energy performance in buildings can mean many different things. Energy intensity, or energy use per unit of floor area, is one common measure of building energy performance. The US EPA ENERGY STAR(TM) Buildings program, with its Portfolio Manager rating system, measures and compares building energy performance through adjusted energy intensity.
As a starting point, developing a simple energy intensity indicator, such as BTU/Gross Square Foot or MJ (or kWh all fuels)/Square Meter, as a benchmark allows for comparing performance of buildings in a region. A variety of other annual energy cost or use benchmarking reports, such as the "Experience Exchange Reports" published by the Building Owners & Managers Administration (BOMA), provide another source of energy cost benchmark data. Prescriptive energy codes, generally based on ASHRAE 90.1 and 90.2, only indirectly produce an energy intensity, via the modeling of a prescribed set of construction elements meeting minimum requirements. In setting up a model, certain environmental design conditions must be held constant; improving energy performance by curtailing levels of service is not allowed nor would it result in acceptable outcomes.
Energy intensity, then, must be balanced against other performance criteria and project requirements — for example, a building with no lights, air-conditioning or mechanical ventilation will have extremely low energy intensity, but will not adequately serve the needs of building occupants. Sometimes this is taken to mean that all occupant complaints about environmental conditions (heating, lighting etc) can only be addressed by higher levels of energy use. This is demonstrably incorrect. Complaints frequently arise from system imbalances, over-conditioning of supply air, or glare from excessive light — all conditions that involve waste of energy. The need to balance the energy intensity indicator with occupant comfort has led some investigators to attempt development of more complex, multi-dimensional building performance metrics that are based on physical parameters and/or surveyed expressions of occupant satisfaction. Such measurement may ultimately provide us with a way of tracking how well the building and its operation is meeting the full set of design expectations.
A challenge in understanding the performance of green buildings is that there is a delicate interaction and balance between the different goals of green buildings. If energy conservation is the only goal in the building, that priority may preclude other environmental attributes that are important, but can result in higher energy usage. For example, extra outdoor air ventilation generally requires additional fan energy to move the air, as well as energy use for conditioning that outdoor air, although use of heat recovery technology can minimize this latter effect Similarly, the fans/pumps used for water reclamation and recycling require more electricity consuming equipment than is typical in most buildings.
An Effort to Bridge the Gap: The US General Services Administration
The US Department of Energy has determined that effective O&M is one of the most cost-effective methods for ensuring reliability, safety, and energy efficiency. As the largest single "landlord" in the United States, the federal government oversees about 500,000 federal buildings. More than $20 billion is spent annually on acquiring or substantially renovating federal facilities, more than $3.5 billion for energy for these facilities, and almost $200 billion for personnel compensation and benefits for civilian employees. This represents an enormous opportunity to transfer the sustainable technologies and practices on a large scale and help transform the marketplace.
With so much to gain in terms of energy, environmental, and economic benefits, it is not surprising that many federal agencies have developed policies to promote sustainable design and operation.
The US Departments of Energy's Federal Energy Management Program (FEMP) has estimated that O&M programs targeting energy efficiency can save 5% to 20% on energy bills without a significant capital investment. Just for federal facilities, operational efficiencies can lower energy costs between US$175 million to 700 million with concomitant reductions in release of greenhouse gases. From small to large sites, these savings can represent thousands to hundreds-of-thousands of dollars each year, and many can be achieved with minimal cash outlays.
For proper use of metered information and effective operations and maintenance of state-of-the-art equipment and controls, industry needs aggressive, structured training programs for operations and maintenance staff and performance ratings of facility managers to become related to energy efficient operations and maintenance programs.
Inadequate maintenance of energy-using systems is a major cause of energy waste in both the Federal government and the private sector. Energy losses from steam, water and air leaks, un-insulated lines, maladjusted or inoperable controls, and other losses from poor maintenance are often considerable. Good maintenance practices can generate substantial energy savings and should be considered a resource.
In addition, O&M program operating at its peak "operational efficiency" has other important implications:
- A well-functioning O&M program is a safe O&M program. Equipment is maintained properly mitigating any potential hazard arising from deferred maintenance.
- In most Federal buildings, the O&M staff are not only responsible for the comfort, but also for the health and safety of the occupants. Of increasing productivity (and legal) concern are indoor air quality (IAQ) issues within these buildings. Proper O&M reduces the risks associated with the development of dangerous and costly IAQ situations.
- Properly performed O&M ensures that the design life expectancy of equipment will be achieved, and in some cases exceeded. Conversely, the costs associated with early equipment failure are usually not budgeted for, and often come at the expense of other planned O&M activities.
- An effective O&M program more easily complies with Federal laws such as the Clean Air Act and the Clean Water Act.
- A well functioning O&M program means not always answering complaints. Rather, it is proactive in its response and corrects situations before they become problems. This model minimizes callbacks and keeps occupants satisfied while allowing more time for scheduled maintenance.
For US Federal Government Buildings, benchmarking is mandated by Federal Executive Orders and Local Laws that require public buildings to lower energy use by 3% per year over the next ten years.
Bridging the Gap between Design and Operations
High-performing buildings need to provide healthy, productive and safe places in which to live and work. Occupants require energy efficiency, improved indoor environment and innovative design and it is an undeniable fact that there are trade-offs between these performance demands. Clearly the most effective way of advancing the building construction industry towards a sustainable balance is through rational analysis of the actual performance.
Getting Quantifiable Design Intent into Operations
A major cause for discrepancy between design predictions and actual performance is the divide between building operators, tenants, and building designers. Only the rarest of projects will include operating personnel in design development phase. "Optimum" design often fails to take into account realities of commercial operation, including elements such as standard practices, O&M budget cuts, labor costs, union jurisdiction, or the final operating program of the building. Design intent must be carefully vetted with the owner's operating personnel, and tenants to ensure that the design takes into account the intended method of operation.
In addition, this communication loop must be closed at the end of the commissioning process, when the design intent must be shared with the operating personnel in order for them to ensure that the building operates as close to the design intent as possible. Bringing designers back on board after occupancy to review and comment on operations happens even less frequently then integrating operators into the design process. This should continue beyond commissioning as even commissioning is not 100% effective. A seasonal or annual review by the original design team can pick up small issues like errors in critical sensors or control elements that greatly impact energy performance.
Each successive project phase — from concept development through design to construction, Tenant Improvements, and finally hand-over to ongoing building operations — embodies the previous phase's Intent and Requirements. Yet how well articulated is this at each phase? Can better attention to clear statements of intent help us to consistently realize our project goals? Are there ways to articulate Intent and Requirements systematically and in terms of quantifiable outcomes? Perspectives from various project phases need to discuss their approaches to, and experiences with, statement of Intent and Owner Requirements.
Understanding the metrics for building environmental performance, and then measuring performance against those "yardsticks" is key to performance improvement. What are key metrics for building energy performance measurement? How are new buildings doing toward targets? Are there major reasons for differences between anticipated and actual performance? What are water use/conservation baselines and metrics, and are new technologies delivering savings? What is a "carbon footprint", and how does one accurately and repeatably quantify and reduce that footprint?
Advanced metering, with appropriate sub-metering for different end-uses and tenants, is an effective means to determine energy usage and measure savings as well as hold different users accountable for their installation of ancillary and process equipment.
Improving Feedback: Incorporating Experience into Design
Our operation and use of buildings tells us a lot about how they really work, what the ultimate users really like and appreciate, and what doesn't work as we might have thought. Capturing this kind of information in a type of "post-occupancy evaluation" is fairly new to the field. And getting it fed back into the design process is even newer. A few firms and organizations have been leading on this — incorporating iterative learning from projects and even getting operational staff involved in the design phase. Their stories are enlightening and instructive.
It is critical to understand the delicate balance between energy use, indoor environmental quality, and other desired built environment features such as water conservation and recycling. The primary function of buildings is to provide healthy, productive and safe places in which to live and work. Clients require energy efficiency, improved environment, and innovative design, but often struggle to balance the trade-offs between them. Reducing the performance expectations for lighting levels, temperature control, daylight, ventilation rates, and redundancy will reduce energy consumption, but too often following design and construction those reduced performance levels are not accepted by occupants.
Performance and comfort concerns often exclude the use of passive systems such as natural ventilation or optimal thermal mass. Operable windows are generally not considered in the design of new buildings because of performance requirements of acoustics, humidity control and air filtration, even if the operational and first cost hurdles can be overcome. There has been a trend over a number of years of increasing the glazing area of buildings due to both client requirements and architectural preference. A common solution to optimize the sometimes contradictory goals of improved indoor environment and reduced energy consumption is a complex set of controls and systems to minimize energy use wherever possible.
However, the often challenging to operate technology and design concepts sometimes fail to deliver on their promised improvements in function and efficiency, and in some cases it has been shown that these concepts and technologies consume more energy initially than the mature technology they replaced. There is a need to better test new technologies in research laboratories and through repeated demonstration projects before they are widely implemented, along with need for monitoring and performance guarantees.
The growing number of initiatives toward building energy performance labeling and benchmarking will help significantly in providing feedback to design teams about what is working (or not). Too often the teams doing the innovative design are never aware of issues that affect operating building energy/environmental performance, so assume that everything works as expected. With more widespread "operational" energy labeling that shows measured performance, and policy moves toward mandatory benchmarking and performance disclosure, the feedback process will become more common place.
Another innovative initiative that holds great promise toward bridging this challenging gap, and deliver measured results in building performance improvements, is the "Green Lease Schedule" effort in Australia. The Green Lease Schedule (GLS) provides for mutual contract lease obligations for tenants and owners to achieve energy efficiency targets, as well as other environmental obligations if agreed (Woodford 2007). The GLS initiative provides a way for tenants to make owners accountable for building energy performance, and also let building owners make tenants accountable for their energy usage. While the effort is relatively new, preliminary findings are extremely encouraging, and this lease structure will likely be a powerful tool in getting feedback about actual energy performance to key design and construction decision makers.
There is growing awareness about the potential gap between expected and actual performance, and a variety of initiatives are underway to better quantify, and then bridge, this gap.
As there is more activity and push to disclose performance data and lessons learned about projects, designers and operators can help to move each other forward on the road to high-performing buildings — with both good intentions and high performance. As more actual energy performance data become available on high-performing buildings, clearer and more realistic expectations will help establish confidence within the building design and construction industry about costs and savings.
Some initiatives such as mandatory operational energy performance benchmarking, and structured feedback activities like the Australian Green Lease program, hold great promise, and will likely spawn other innovative activities that bridge the energy performance gap.
With growing efforts toward building energy labeling and in some cases, mandatory energy performance disclosure, there is great opportunity for combining both the "asset" rating of a building, where the physical properties and predicted optimal performance are calculated, together with the "operational" rating, which measures how the building actually performs. Through a combination of these two ratings: how the building should perform, and how it actually is consuming energy, operators and designers will be able to learn what works, and where there are opportunities for significant savings.
- Camilleri, M.J. and R.A. Jaques, "Study Report No. 96 (2001): Implications of Climate Change for the Construction Sector: Office Buildings", BRANZ 2001, the Resource Center for Building Excellence, New Zealand
- Learning from Our Buildings 2001. Learning from our Buildings: A State-of-the-Practice Summary of Post-Occupancy Evalution. Federal Facilities Council Technical Report No. 145, National Academy Press, 2001.
- New Buildings Institute (NBI) 2008. Energy Performance of LEED NC Buildings, February, 2008, accessed from
- US Department of Energy — Office of Energy Efficiency and Renewable Energy, Federal Energy Management Program (FEMP) — Operations & Maintenance.
- Woodford, L (2007). The Green Lease Schedule, in Proceedings of the ECEEE Summer Study. European Council for an Energy Efficient Economy, 2007.
- This paper was initially authored for the Building Performance Congress, which took place in Frankfurt, Germany 7–11 April 2008.
Michael Bobker is the founder and Director of the CUNY Building Performance Lab. He has worked in various capacities in building energy efficiency work in NYC for over 25 years, including project development and implementation, training, and new product development. He holds Masters degrees in social science and in energy management.
Adam Hinge manages Sustainable Energy Partnerships, a small consulting firm specializing in energy efficiency program and policy issues. Hinge works as an advisor to utilities, government agencies and others in developing energy efficiency market transformation initiatives, is a consultant to major commercial sector energy consumers, and is an Adjunct Research Scholar in Columbia University's Urban Energy Program.
Dr. Om Taneja is a licensed professional engineer in New York and New Jersey. He is employed by the United States General Services Administration as Director of Manhattan Services Director where he oversees the operations, maintenance and renovations of more than 10 million square feet of commercial and judicial facilities. After working with a utilities generation and distribution company, Dr. Taneja worked with a consulting engineering firm and then moved on to facilities management. He worked for more than 20 years as a facilities manager as Chief of Planning, Design and Overseas Properties for the United Nations, NBC and hospitals. He has a Bachelors and Masters Degree in Mechanical Engineering and Ph.D. in Operations Research.