Mike Opitz PE, LEED AP
Certification Manager, LEED for Existing Buildings
U.S. Green Building Council
Introduction
Rising and fluctuating energy prices are a strong motivator of change for facility managers. Limited operating budgets make price shocks tough to absorb, and trying to predict what prices will be doing next year can be an exercise in futility. If you pay real-time prices this is a daily challenge, but even if you have a utility rate contract you’ll have to face the issue when it’s time to renew.
Reducing your energy use through improved efficiency is a well-known strategy for reducing energy costs and managing energy cost risk. It also has impressive sustainability benefits because of reduced fuel consumption and emissions. Let’s say you’re on top of this and have already benchmarked your building and determined that it’s not performing as well as its peers in the U.S. Let’s also say your organization has already decided to make a concerted effort to reduce your energy costs. Now you need to determine which specific things need to be done to make your building perform better.
What you need is a formal energy audit of your facility.
Why Careful, Thorough Energy Audits are Important
Investigating and prioritizing the energy savings opportunities in your building should be done methodically, not randomly based on intuition. It’s tempting to read an article or attend a seminar, get all fired up about saving energy in your building, jump wholehearted into the first few strategies that come to mind, and call it a done deal. Don’t do that. The rewards you reap from energy savings programs depend critically on how thoroughly you investigate your building to discover and assess all the ways your building is wasting energy.
Some forms of energy waste are small but obvious, others huge but hidden. Some waste is cheap and easy to fix, some requires substantial effort and large capital investment. Some waste should be remedied immediately, independently of anything else going on, while some is best reduced in conjunction with other building improvements and must be integrated into an overall facility management plan. Some strategies will reliably deliver energy savings year after year with little or no active involvement from facilities staff; others are high-risk and require constant vigilance. Some strategies offer secondary benefits for safety, comfort, air quality, and system reliability, while others don’t.
In short, identifying and sorting through all the available energy saving strategies for your building is a complex technical and economic enterprise, one worthy of careful attention and taking enough time to do a good job. This doesn’t mean hours or days, but weeks or months. For a large, complex facility it could even take a year! This is what a good energy audit and follow-up analysis accomplishes.
Types of Energy Audits and What they Tell You
Energy efficiency experts generally recognize three levels of energy audits depending on the time and effort spent during the audit and analysis:
- Level I, basic — also known as the “one-day” or “walk-through” audit, this approach involves a cursory analysis of energy bills and a brief survey of the building to produce a rough estimate of how efficiently energy is used in the building. This level of effort will detect at least some of the “low-hanging fruit” and may suggest other options worthy of more study, but should never be viewed as comprehensive. Although this option is easiest it also produces the crudest results, so don’t be tempted into thinking you’re done once you do this much — you’ve really only gotten started.
- Level II, intermediate — by investing more effort in the building survey and energy analysis and by adding in some system performance testing, this method provides a breakdown of how energy is used in the building as well as a broader range of savings options, including simple capital investments. It accounts for the “people factor” and its effect on uncertainty of savings, and also explores maintenance procedures and assesses any impacts savings measures may have on them. Many facilities will find this level of analysis to be sufficient.
- Level III, advanced — also known as the “investment-grade audit”, this analysis digs into the details of any large capital projects you may be considering as a result of previous, simpler audits. Even more detailed data is gathered from field equipment, extensive test measurements are taken which may include spot-measurements and short-term energy monitoring, possible risks are assessed, and intensive engineering and economic analysis produces reliable estimates of project energy and financial performance with the high confidence needed for major capital projects.
These audit approaches tend to overlap in practice. All three assess the potential energy savings and initial cost of various energy savings strategies, so in that sense all are similar. The differences are in your confidence that you’ve truly found all your savings opportunities, the accuracy of the expected savings and initial cost, and how much information you have about the difficulty of project implementation and the likely persistence of the savings over time. The devil is definitely in the details.
All level 2 and level 3 audits involve collecting general building data (location, size, usage type, energy sources), historical energy use data, and energy systems data (type of equipment in the envelope, lighting, HVAC, service water, etc.) to get a description of the facility. The more detailed the available data is, the more complete this description can be. For example, submetering within a building makes it easy to call out specific end uses or facility areas, and having daily or even hourly consumption data allows you to call out time patterns normally buried within the monthly billing cycle.
All this data then feeds an energy use analysis that lays out how much energy is consumed for each major end use in the building, such as space heating, space cooling, lighting, air distribution, etc. This defines a baseline scenario for future years if no energy projects are undertaken. A similar analysis can be done with respect to peak energy demand.
This represents the lion’s share of the work needed to plan energy projects. With these results in hand it becomes a relatively easy matter to identify and rank the best energy projects for your facility.
Tips & tricks
Perhaps the most important requirement of a good energy audit is to keep a whole-building perspective in mind. First and foremost this means starting your analysis at the energy end uses and working your way “upstream” in the energy delivery chain in what’s known as end use analysis, bottom up analysis, or starting at the end, not the beginning.
You start by examining energy services delivered to the building’s spaces and ask basic questions: do we need this service at this location? If so, how often and how much? From there you assess how well the terminal equipment supplying that service is working, and so on for the distribution equipment, generation/conversion equipment, and the controls on each of these. Since each step in the energy chain introduces losses, saving one unit of energy at the end use saves more than one unit at the generation/conversion equipment because of the multiplier effect. A simple example of this is fixing a leaky steam trap, which may save 1.5 or more units of fuel energy at the boiler for each unit of heat saved at the trap because of losses from leakage, uninsulated pipes, and boiler inefficiency.
Unfortunately many energy audits are done in exactly the opposite way: they’re “top-down” analyses that start at the boiler because it’s an obvious piece of energy equipment that’s easy to understand and explain, but minimize investigation of how the heat is used within the end-use spaces. Resist the temptation to stop your analysis at that level.
Here are a few other ways to get the most out of your energy audit:
- Don’t rush it! A good site survey, equipment testing, and follow-up analysis takes time. This has been mentioned several times already, but it bears repeating.
- Key to success are the effort and skills of the auditor. If you’re a building energy guru then go for it, but if not, by all means hire an independent specialist. All energy auditors are not created equal, so shop carefully and be sure you’re comparing similar levels of thoroughness and quality when soliciting bids. Assess whether the auditor is truly independent, or whether he has something to gain if you purchase new equipment.
- Be rational, analytical, and holistic about selecting your energy saving measures. Don’t home in on the ones that seem most exciting, easiest, or most visible to the exclusion of others.
- Don’t focus exclusively on major equipment that’s near the end of its useful life. Usually the most effective rule of thumb for saving energy is to avoid supplying it in the first place when it’s not needed. This means lots of energy can be saved simply by changing operational practices, either at no initial cost (disabling equipment when the space is unoccupied) or at low initial cost (automatic controls that modulate equipment output or turn it off depending on space conditions).
- Keep maintenance in mind throughout. This can be the difference between a reliable energy project and one that’s riddled with problems.
- Develop an energy management plan and keep a long-term perspective. Design your audit and prioritize its results assuming your organization will occupy your facility indefinitely. Energy waste is a condition that constantly tries to return; plan and implement your savings strategies to prevent this.
Conclusion
If you’re serious about saving as much energy cost as possible with the quickest payback time and least hassle, take the time to plan your energy projects right. Perform a good energy audit, and assess its results carefully based on the needs of your facility, whether based on annual savings, initial cost, payback time, synergistic comfort benefits to occupants, or recurring maintenance hassle. The rewards are well worth the work.
Resources
American Society of Heating, Refrigeration, and Air Conditioning Engineers (www.ashrae.org), Applications Handbook, 2003.
Wulfinghoff, Donald, (www.energybooks.com), Energy Efficiency Manual, 1999.
American Society of Heating, Refrigeration, and Air Conditioning Engineers (www.ashrae.org), Procedures for Commercial Building Energy Audits, 2004.