Elizabeth Ratner 2017-05-12 02:41:43
Recent years have seen tremendous strides in building energy use reduction, but what does it take to make existing buildings net zero energy? The answer is merely a few simulations away and could mean greater comfort for occupants and unprecedented long-term value for owners. Over the last decade, we’ve seen a steady increase in the number of projects across the country striving to annually produce as much energy as they consume. They’ve done this by decreasing the building’s energy demand to record lows, then off setting that demand with renewable energy like photovoltaics. In 2015, the U.S. Department of Energy (DOE) issued a common definition for zero-energy buildings (ZEB) to bring clarity to the designation. The definition states a ZEB is “An energy-efficient building where, on a source energy basis, the actual annual delivered energy renewable exported energy.”is less than or equal to the onsite This means that after conversions are completed for the different types of energy employed, just as much energy must be generated from the site as is consumed on the site each year. But why would anyone bother trying to meet this seemingly difficult target? Three main reasons rise to the top: 1 OCCUPANT COMFORT. Buildings are for people, first and foremost, so the top priority must always be their comfort and satisfaction. Fortunately, many building characteristics that people find most enjoyable also lower energy use. Increasing natural daylight in the space and dimming the lights, tightly sealing the envelope to normalize the temperature from the perimeter to the core, and using displacement or convection heating, ventilation and air-conditioning (HVAC) systems to more naturally condition the space are all energy-reducing strategies that can result in rave reviews from occupants. 2 ECONOMIC BENEFIT. While there will always be an investment upfront, payback has been shrinking for most technologies, and this is only bolstered by utility incentive programs. Never undertake a project without checking on the incentives offered by the local utility. Once the building is up and running, achieves zero energy for a year, and reaches the payback periods, not only will the owner never have a utility bill but he may also make money if the photovoltaics generate more energy than the building consumes. Possibly the greatest economic benefit, though, is long-term protection from utility rate hikes. 3 DATA COLLECTION. Buildings have been getting smarter with the rise of building automation systems, but smart sensors are now having their day. Technologies like power over Ethernet lighting may not only further reduce energy demand, but also use sensors that capture and respond to multiple inputs. These sensors can, for instance, manage dimming for daylight harvesting while also mapping occupancy patterns. Sensors on HVAC equipment tied to management platforms can send alerts when an element is not performing optimally. All of this information both contributes to energy savings and provides insight into the use and performance of various aspects of a building. 10 Steps Toward Zero Energy The following 10 steps serve as a guide for navigating the path to zero energy for existing buildings. Each can be modified given the level of retrofit to be undertaken, and each can serve as a feasibility check to ensure zero energy makes sense for the project. 1 COMMIT TO FLEXIBILITY. This is the most important step of all and requires a commitment from each member of the team. New systems, materials and technologies may have to be employed to achieve the goal and this must be embraced by everyone involved. Without flexibility and compromise, the holistic building cannot be truly optimized and zero energy will not make economic sense. 2 STUDY CURRENT LOADS IN DETAIL. Dig deeply into the current energy use of the building, adding submeters and data-collecting power strips to the extent possible. It is only with a detailed profile of energy use that the team can begin trimming the demand. How much energy do the average workstations and break-rooms consume? Which equipment is being left running when not in use? 3 TEST ENERGY REDUCTION STRATEGIES. Now it’s time to brainstorm energy reduction strategies and engage a professional energy modeler. Be sure to test both changes in equipment as well as changes in occupant use patterns. It’s also important to look for synergies among proposed strategies to see if two strategies together total a greater energy savings than the mere sum of their parts. Finally, be sure the modeler runs the simulation with multiple weather files, including the past 15 hottest years and projections of future years. The simulation should hit zero energy under all reasonable weather circumstances. 4 ESTIMATE RENEWABLE ENERGY POTENTIAL. As the how-low-can-you-go energy simulations are being run, engage the help of a photovoltaic installer to run quick calculations on energy generation potential for eligible roof and canopy areas. These calculations will provide an annual energy budget for the building and thus a target for the simulations. Be sure the final photovoltaic system is sized 10 to 15 percent larger than the estimated annual energy demand so it’s able to absorb any unforeseen spikes in energy use. 5 SET-UP AN ALERT SYSTEM. None of this hard work will pay off if systems or sensors malfunction, aren’t caught and corrected in a timely manner, and therefore increase energy use unnecessarily. For this reason, it is essential that a robust alert system is put in place to notify the facility manager immediately when maintenance issues or system errors arise. The alert system should monitor both building systems and the photovoltaic system to ensure the building is always using the least and producing the most amount of energy at a given time. 6 IDENTIFY UTILITY INCENTIVES. Many utilities have incentive programs for energy-efficient strategies that seem to get increasingly better each year. Always check the local utility’s program details before embarking on any kind of capital improvement to take full advantage of the benefit. On a large retrofit, this can mean hundreds of thousands of dollars in incentives, which can significantly quicken the pace of a payback for efficient technologies. Be sure to apply early, though, because some incentives must be approved before new equipment is purchased. 7 CALCULATE PAYBACK. Best practice is to keep track of rough first costs from the start so the design doesn’t become dependent on out-of-budget technologies, but this step is focused specifically on expected payback. Work with the energy modeler to calculate payback time using first cost, utility incentive estimate, and predicted annual energy savings for each set of new equipment. Determine the payback length the owner is comfortable with and filter out strategies that don’t comply. 8 EDUCATE AND EMPOWER OCCUPANTS. Occupant behavior is often overlooked in energy-efficiency upgrades because it’s viewed as unpredictable or untouchable, but most zero energy building owners tout it as critical to success. As with any kind of human behavior, best results are achieved when people are educated and empowered, so be sure to incorporate both on a consistent basis. Some zero energy buildings, for example, give occupants a menu for their workstation that identifies the power consumption of each type of equipment and allots each workstation an energy budget. It’s up to the individual to select which pieces of equipment to have at their workstation within that budgeted amount. Then, go a step further and supply each workstation with a power strip that records energy use and recognize employees with the lowest usage. 9 WATCH THE NUMBERS LIKE A HAWK. Once the new systems and technologies are installed, the photo voltaics are up and running, the alert system is live, and the occupants are fully engaged, start watching the numbers attentively. Is the building tracking at, better, or worse than the energy model predicted? Is the weather cooperating, or is it a particularly cloudy year? If so, proactively circulate ideas for trimming energy use on overcast days and get the occupants involved in forming new habits. 10 VERIFY/CERTIFY THE PROJECT. Early in the design process it’s important to decide whether the building will be verified or certified zero energy. As of this publication two options exist: 1) verify the building through the New Buildings Institute, or 2) certify the building through the International Living Futures Institute. In either case, consider registering the project with the New Buildings Institute as a Zero Net Energy Emerging Building before occupancy so it may be added to their comprehensive tracker. Once the building achieves net zero energy status over 12 consecutive months, it’s time to complete the verification or certification and go public with the success story! Myth Busting Even though the number of zero energy buildings is growing and spreading across the country, it’s still a fairly rare phenomenon due to a few myths. ONLY NEW CONSTRUCTION CAN ACHIEVE ZERO ENERGY. Any building, no matter the age, can be verified zero energy as long as it meets the DOE’s definition. DPR Construction, for example, has transformed three existing buildings to zero energy for its regional offices in Phoenix, San Francisco and San Diego. They did this by editing the building envelopes, systems, floor plans, and beyond. Consider as an other example, buildings that are built to be zero energy-ready, meaning the annual energy use is low enough to be offset by onsite renewables, but don’t install the photovoltaics until several years after occupancy when budget is available. For buildings that achieve very low energy use but not zero energy, the New Buildings Institute also offers an Ultra-Low Energy Verification. ONLY SMALL PROJECTS CAN ACHIEVE ZERO ENERGY. While most of the currently verified zero energy projects are smaller than 25,000 square feet, this is likely to soon change. The New Buildings Institute also tracks buildings that are pursuing zero energy verification but have not yet reached the 12 consecutive months of zero energy status. The current batch of ZNE Emerging buildings is evenly distributed in terms of size with a significant number of projects larger than 100,000 square feet.2 ZERO-ENERGY PROJECTS REQUIRE A LARGE COST PREMIUM. They can, but they don’t have to! Remember the first step in the 10 steps toward zero energy that you just read? COMMIT TO FLEXIBILITY. You'll have to make tradeoffs and compromises to achieve zero energy within a typical budget, but it can be done. The Lincoln Heritage Public Library Chisney Branch in Chisney, Indiana, USA, didn’t have money for operating expenses (utilities or staff ), but had raised funds to build a modest library. They had no choice but to make the project zero energy and were willing to make tradeoffs with the design team to achieve the goal and realize their dream of a community library.3 ZERO-ENERGY PROJECTS ONLY PENCIL-OUT ON THE U.S. WEST COAST WHERE THE CLIMATE IS TEMPERATE AND UTILITY RATES ARE HIGH. Only 23 of the 53 buildings verified zero energy in the New Buildings Institute’s 2016 List of Zero Energy Buildings are in California, Oregon or Washington,4 so the strategy is obviously penciling-out in other parts of the country, as well. Some projects may have longer paybacks, but owners and design teams are finding ways to make the projects viable in many different climate zones and utility districts. Zero-energy buildings represent an exciting new frontier in the building industry and are only expected to grow in number. Given that they offer such wide-ranging benefits — from increased occupant comfort to long-term operational cost savings to valuable data collection — it is a great idea to take every building through the 10-step process listed here to check the feasibility of a zero-energy conversion. Zero-energy verification could be in your future! REFERENCES 1) DOE, “A Common Definition for Zero Energy Buildings.” 2) NBI, “2016 List of Zero Net Energy Buildings.” 3) High Performance Buildings Magazine, Summer 2014, “Community Connection,” by Daniel Overbey and William Brown, pages 30-34. 4) NBI, “2016 List of Zero Net Energy Buildings.” ELIZABETH RATNER, AIA, LEED AP BD+C, is the director of the Center for Building Performance at Little. She creates measurably better environments for occupants and greatest value for owners by using robust simulation techniques to drive and numerically validate improvements in design. Projects range from deep retrofits to new construction and include net-zero-energy buildings and projects pursuing Living Building Challenge and WELL certification
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