Commercial buildings are among the top energy users in the United States, accounting for about 18% of the total energy consumption in 2022. According to the Commercial Buildings Energy Consumption Survey (CBECS), the estimated 5.9 million U.S. commercial buildings consumed 6.8 quadrillion British thermal units (quads) of energy and spent $141 billion on energy in 2018. Electricity and natural gas were the main energy sources, and space heating accounted for close to one-third of end-use consumption.
Reducing energy consumption in commercial buildings can have multiple benefits, such as lowering operating costs, improving occupant comfort and productivity, enhancing building performance and resilience, and mitigating environmental impacts. However, achieving these benefits requires a comprehensive and systematic approach to energy conservation that considers the building design, operation, maintenance, and retrofit.
In this article, we will discuss some of the key strategies for energy conservation in commercial buildings, and how facility managers can implement them effectively. We will also provide some examples of best practices and case studies from various building types and sectors.
Strategy 1: Optimize Building Envelope
The building envelope is the physical barrier that separates the indoor environment from the outdoor climate. It includes the walls, roof, windows, doors, and insulation. The building envelope plays a critical role in determining the heating and cooling loads of a building, as well as its daylighting potential and air quality.
Optimizing the building envelope can reduce the energy demand and improve the thermal comfort of a building. Some of the common measures for optimizing the building envelope are:
- Selecting high-performance materials that have low thermal conductivity, high reflectivity, and high durability.
- Improving insulation levels and eliminating thermal bridges that cause heat loss or gain.
- Installing high-efficiency windows that have low emissivity coatings, double or triple glazing, and appropriate shading devices.
- Sealing air leaks and cracks that cause infiltration or exfiltration of conditioned air.
- Incorporating passive solar design principles that utilize solar heat gain in winter and minimize it in summer.
For example, the U.S. Coast Guard Training Center in Petaluma, California, used passive solar design and high-performance building envelope materials to achieve a 50% reduction in energy use compared to a conventional building. The building features a south-facing orientation, large overhangs, operable windows, low-e glazing, high R-value insulation, and cool roof materials.
Strategy 2: Upgrade HVAC and Lighting Systems
Heating, ventilation, and air conditioning (HVAC) and lighting systems are the major energy consumers in commercial buildings. According to CBECS data, HVAC accounted for 32% and lighting accounted for 17% of total end-use energy consumption in commercial buildings in 2018. Therefore, upgrading these systems can have a significant impact on energy savings.
Upgrading HVAC and lighting systems can involve replacing old or inefficient equipment with new or more efficient models, installing advanced controls and sensors that adjust the system operation based on occupancy, temperature, humidity, daylight, or other factors, and optimizing system design and configuration to match the load requirements and distribution.
For example, the Empire State Building in New York City underwent a comprehensive retrofit project that included upgrading its HVAC and lighting systems. The project involved installing variable frequency drives for fans and pumps, retrofitting chillers with variable speed compressors, replacing air handling units with demand-controlled ventilation, installing wireless thermostats and occupancy sensors for individual zones, replacing fluorescent lamps with LEDs, installing daylight harvesting controls for perimeter zones, and implementing an integrated building management system. The project resulted in a 38% reduction in energy use and $4.4 million in annual savings.
Strategy 3: Implement Renewable Energy Sources
Renewable energy sources are those that derive from natural resources that are replenished by natural processes. They include solar, wind, hydro, biomass, geothermal, and others. Renewable energy sources can provide clean and low-cost energy for commercial buildings, reducing their dependence on fossil fuels and their greenhouse gas emissions.
Implementing renewable energy sources can involve installing onsite generation systems such as solar photovoltaic panels, solar thermal collectors, wind turbines, or geothermal heat pumps that produce electricity or heat from renewable resources. Alternatively, it can involve purchasing renewable energy certificates (RECs) or participating in green power programs that support renewable energy generation from offsite sources.
For example, the National Renewable Energy Laboratory (NREL) Research Support Facility (RSF) in Golden, Colorado is a net-zero energy building that produces as much energy as it consumes on an annual basis. The RSF uses a combination of onsite renewable energy sources such as rooftop solar photovoltaic arrays (2.5 MW), transpired solar collectors (16 kW), ground-source heat pumps (600 tons), and offsite renewable energy sources such as wind power (1.6 MW) and biogas (0.8 MW) to meet its energy needs.
Strategy 4: Monitor and Manage Energy Use
Another way to conserve energy in buildings is to maximize the efficiency of the energy systems and equipment. This means using less energy to provide the same or better level of service or comfort. For example, replacing incandescent light bulbs with LED bulbs can reduce the electricity consumption for lighting by up to 80%. Similarly, installing high-efficiency heating and cooling systems, such as heat pumps, can reduce the energy use for space conditioning by up to 50%. Maximizing efficiency also involves optimizing the operation and maintenance of the energy systems and equipment, such as adjusting the thermostat settings, cleaning the filters, and repairing any leaks or malfunctions. By maximizing efficiency, building owners and occupants can save money on energy bills, improve the indoor environmental quality, and reduce greenhouse gas emissions.
Monitoring and managing energy use is an essential strategy for energy conservation in commercial buildings. It involves collecting, analyzing, and reporting data on energy consumption, performance, and costs, and using this information to identify opportunities for improvement, implement corrective actions, and evaluate the results.
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Monitoring and managing energy use can involve installing smart meters, submeters, or other devices that measure and record energy use at various levels of granularity, such as by building, system, zone, or equipment. It can also involve using software tools or platforms that aggregate, visualize, and benchmark the energy data, and provide feedback, alerts, or recommendations for optimization. Furthermore, it can involve establishing policies and procedures for energy management.
Building energy conservation is a crucial issue that affects the environment, the economy, and the society. By applying the four strategies discussed in this article, building owners and occupants can reduce their energy consumption and environmental impact, while improving their comfort and well-being. However, implementing these strategies also involves some challenges, such as technical, financial, and behavioral barriers. Therefore, it is important to raise awareness and provide incentives for building energy conservation, as well as to support research and innovation in this field. Building energy conservation is not only a responsibility, but also an opportunity to create a more sustainable and resilient future.
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