Energy Optimization In Existing Buildings
The importance of focusing on energy optimization in existing buildings is crucial to reducing energy consumption and greenhouse gas emissions. In the U.S., existing buildings represent 85-90% of entire building stock (75+ billion sqf t). Buildings are responsible for an estimated 40% of U.S. primary energy use, 72% of electricity consumption, 39% of carbon emissions, and1 13.6% of potable water consumption.
Existing buildings typically have aging building systems and infrastructure that present opportunities for energy optimization, yet they often have limited capability or lack of building management systems. In addition, a significant number of existing buildings are historic buildings, presenting additional obstacles with respect to historic preservation during energy retrofit projects.
New research by Lawrence Berkeley National Laboratory (LBNL) has found that the cost of saving energy through these means is less than half of constructing a new coal plant to generate the same amount of electricity.?
This should not come as a surprise to anyone. So why then are we spending more money to build more and more power plants and still trying to generate more energy when we should be spending more money to save energy? Fortunately, energy efficiency is gaining major traction across all sectors. In 2014, 85-95% of building construction spending was in total major renovation/retrofits, up from 66-75% in 2009.2 This trend will continue to improve in 2015 and beyond. Even “Big Oil” has joined in, and now major oil companies such as Shell and BP have a green component in their portfolio. So what does this mean for the future? Only time will tell, although early indicators are positive.
Proactively managing the energy efficiency and sustainable elements of buildings during the design and preconstruction phases of an energy retrofit project has a profound impact on the long-term Triplex Cost Considerations of a building: financial, social, and environmental. Studies and research substantiate claims that high-performance buildings must also balance program, owner, occupant, operator, community, budget, and schedule requirements from a truly holistic standpoint. Let’s look at some essential tools and concepts for achieving these objectives.
Lifecycle Cost Analysis
Design teams can use energy modeling, or calibrated energy models using utility data, to determine and benchmark the actual energy consumption of a facility before the retrofit. The model can then be adjusted to factor in Energy Conservation Measures (ECMs) and their associated impact on energy consumption of the building.
Life Cycle Cost Analysis (LCCA) is a practical method and a guideline for evaluating the economic performance of building service systems. LCCA balances the long-term operations and maintenance with the initial cost budgetary concerns of the project. Several factors are considered when calculating LCCA, which requires information from several key team members. Estimators and contractors can provide the initial cost of the equipment, including materials, installation, delivery, etc. The manufacturer can provide maintenance and utility consumption requirements which can then be applied to local rates and tariffs; however, the latter is best obtained by performing a Whole Building Energy Model (WBEM).
Finally, replacement costs and overhaul information are also factored to understand the full financial implications of a given system. Each building system can be analyzed as such to calculate the cost of ownership. The hourly-based LCC results indicate that as efficiency increases, the lifetime operating cost has greater impact on the LCC than the total installed cost. In other words, the increase in total installed cost that occurs when equipment efficiency is increased is offset by the decrease in lifetime operating costs.
A whole-building retrofit integrated approach is equally as important to successful building performance as efficient mechanical systems are. High-performance building retrofits will use less material more effectively, are more durable, and require less maintenance.
Requirements for High-Performance Building Retrofit
- Entire design and Construction team, O&M staff, and owner to be part of retrofit process from the start.
- Retrofit to meet OPR (Owners Project Requirements).
- Whole building is approached as one system.
- Use of energy modeling to predict energy consumption of ECMs.
- Economic decisions must include life-cycle costs.
- Energy, resources, and materials to be used efficiently.
- Use durable material that requires less maintenance and are recyclable.
- Incorporate QA process of commissioning into the retrofit and delivery process.
Measurement & Verification
Through real-time monitoring, measurement, and verification through metering and submetering, associated facilities will be able to have a full pulse on building systems energy consumption. Why is this important? It goes back to the industry cliché, “you cannot manage what you cannot measure.” Having this data available in real time will drive energy optimization by immediately identifying operational anomalies and drift in equipment scheduling and performance.
Building performance data should be used to:
• Drive and inform operational Energy Conservation Measures (ECMs) in real time and not until building performance is adversely affected
• Inform and optimize building operations and maintenance
• Continuously commission building systems and enable fault detection diagnostics
A 6-8% reduction in energy consumption and associated GHG emissions can be achieved through implementation of low-cost/no-cost operational energy conservation measures. Examples of typical operational ECMs are:
• Educational campaign and occupant behavior training
• HVAC equipment re-scheduling and re-tuning
• HVAC equipment temperature set backs
• Supply temperature and static pressure seasonal resets on HVAC equipment
• BAS troubleshooting and commissioning
• Zone temperature optimization
• Chilled Water and condenser water temperature resets
• T-8/12 lighting fixture upgrades to LED
• Air and waterside economization
• Plug load control
Efficiency Allies: Occupants And O&M Staff
More than one-third of new commercial building space includes energy-saving features. However, according to a paper published in the journal Building and Environment, without training or an operator’s manual, many occupants are in the dark about how to use them.3
This is very interesting indeed, but not surprising. All too often, we focus all our efforts on ECM identification and implementation and forget about the end user and occupant training. We have to remember that the biggest impacts on building performance improvement are the occupants and their behavioral patterns. Occupant training and engagement is crucial to driving down energy consumption in buildings.
So the question then arises as to when and how this training should be conducted.
Ideally, you would like to involve occupants, or an occupant representative, as early as possible during the design phases of a retrofit project. This is important, as it will help convey the optimum complexity of a certain ECM in terms of combining technical features with likely effective operation by the actual personnel. Early engagement will also help inform the team when and how much training will be required for each associated ECM. For select, more complicated ECMs, video training is recommended to allow ease of accessibility when and if complications occur.
As for maintenance, 20% of the asset lifecycle cost is in design and construction, and 80% is in O&M costs. O&M readiness is a project delivery process that brings lessons learned for asset management into the design and construction process.
The process includes:
1) Improved turnover process
2) Attention to facility manager’s needs and interests
3) Informed life cycle cost decisions
4) Informs the design and construction professionals similar to constructability analysis or mock ups
The DOE in a recent study has stated that preventative maintenance can save an average of 15% on O&M costs and predictive maintenance can save an additional average of 10% on O&M costs. It is important to include an O&M plan early in the design phases of the retrofit project, to reduce lifecycle costs, reduce risk, ensure data quality, and sustain investment in commissioning and LEED programs.
During the design and design reviews, it is crucial to involve O&M specialties, including the commissioning agent. In order to maintain durability and efficiency of building systems, especially mechanical systems, it is important to ensure that the commissioning plan is in place early, and that the equipment is commissioned prior to substantial completion. In order to maintain efficiency building, systems have to be continuously commissioned. It is also important in these stages to conduct thorough serviceability reviews to ensure safe and easy access of equipment.
M&V And The Hawthorne Effect
Real-time measurement and verification (M&V) through building metering and submetering — including energy, waste, and water consumption — is essential in both proving performance and driving building performance optimization. This helps immediately identify any anomalies noticed from the consumption profiles, such as spikes in and dips in consumption. Furthermore, real time M&V helps operators and engineers drive building performance and identify low-cost or no-cost conservation opportunities.
The data collected from buildings is priceless; it can be normalized for both weather and occupancy using linear regression analysis. This is important in accurately baselining building consumption to account for variances in weather, building use, and occupancy. Every building is different and has its own personality, and as such should be treated uniquely. Building performance optimization has to balance social, economic, and environmental requirements. Optimization should never come at a cost of adversely affecting occupant health and comfort.
According to a recent study by Carnegie Mellon University, building occupants who monitored their energy use and automated the timeframe for specific devices to turn on and off significantly reduced their energy consumption4. This takes the Hawthorne Effect5 to a whole new level. Observing individuals to effect change is one thing, but now observing and allowing individuals to control systems is a different dynamic that can spur tremendous gains in energy efficiency. The Hawthorne Effect alone could only reduce consumption by 7%. Adding energy-use dashboards and control added 30% more. This is amazing and speaks to the power of an informed user, as well as to the importance of availability of data. There is a plethora of data that can be mined from buildings. The challenge has been to make meaningful sense of this data and use this data to drive energy optimization to affect change.
The above study proves that empowered with the correct data and with the ability to control environments, users/occupants can reduce consumption by more than fivefold. Submetering and data mining from building management systems is a crucial first step to collecting building data. The next step would be to present this information in a user-friendly format that users can easily comprehend. The last step would be to enable users to have a level of control that will allow them to actually reduce consumption.
While the above study focused only on plug loads, we can take this control to a higher level and focus on temperature, humidity, and lighting levels. Of course, this control has to stay within certain prescribed boundaries and constraints to maintain allowable comfort levels (temperature, humidity, and lighting levels), but the potential gains remain.
There is no single path to a high performance building retrofit; enhanced collaboration and team commitment is paramount. Experience is valuable in teams designing high-performance building retrofit projects. Energy modeling is recommended, but not required, to benchmark the building, inform the retrofit, and monitor post-occupancy. Measurable goals should be established early and accomplished throughout the duration of the retrofit project.
In the end, a fundamental measure of every retrofit project is whether it can make good business sense and good environmental sense while remaining easy to maintain.
1. U.S. Geological Survey (2000). 2000 data
2. McGraw Hill Outlook 2011