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Energy is fundamental to the services and amenities we expect from buildings. Effective building operations and management requires managing energy use and supply based on a range of critical objectives, including:
21st-century building energy management presents complex challenges that require understanding interconnected building and energy supply systems, like the electricity grid. Tools like building automation systems can greatly enhance operations and management effectiveness when properly deployed and used.
For federal renewable energy purchases, 42 U.S.C. § 15852(b) defines renewable energy as electric energy generated from solar, wind, biomass, landfill gas, ocean, geothermal, municipal solid waste, or new hydroelectric generation capacity achieved from increased efficiency or additions of new capacity at an existing hydroelectric project. Explore the Better Buildings Initiative’s Renewable Energy Resource Hub for more renewable energy resources.
A refrigerant is a substance used to provide cooling in the refrigeration cycle. The most common refrigerants being produced today are a variety of hydrofluorocarbons or HFCs and non-halogenated hydrocarbons. Chlorofluorocarbons or CFCs and hydrochlorofluorocarbons or HCFCs are being phased out due to their ozone depletion and global warming effects. Learn more about refrigerants and safe alternatives.
Key strategies for reducing energy use and cost related to lighting are:
Learn more about lighting strategies and other efficiency measures you can implement by reviewing Better Building Initiative’s efficient technologies.
Plug loads account for 25% or more of total energy consumption in a building. Strategies for reducing energy consumption from plug loads include:
An energy management information system is composed of devices, data services, and software applications that monitor, analyze, and control metered building energy use and system performance. Elements of an energy management information system or EMIS [PDF] work together to aggregate facility data and help federal energy managers optimize energy use at the building, campus, or agency level. Learn more about energy management technologies.
The components of a building structure that separate and protect us from the elements outside — windows, walls, roofs, etc. — constitute the building envelope or enclosure. To be energy efficient, a building must also be air-tight. When the building envelope allows air to penetrate it, heat and moisture from outside can circumvent thermal insulation and vapor control layers. Accordingly, “leaky” buildings incur larger loads on heating, cooling, and dehumidification systems. Poor performing building envelopes can also compromise occupant health and performance by allowing for mold, moisture, pests and other threats to infiltrate the occupied space.
Appropriate insulation and vapor barriers within walls and roofs and around doors and windows is essential to maintain effective envelope performance. Prioritize materials with a high R-Value, which indicates the ability of a material or assembly to resist the conductive flow of heat.
Pay particular attention to material and assembly transitions and connections, auxh A where walls meet doors, windows, floor or foundation, and roofing system, to control air leakage. For example, keep air, heat and moisture transfer through and around the window as low as possible by specifying windows with low leakage rates, low solar gain, a low U-Value, and a high R-value, meaning, it has well insulated glass. Consider exterior shading for high solar heat gain locations and interior shade management to optimize daylighting, reduce solar heat gain, and mitigate winter heat loss. Learn more about space reconfiguration, renovation, and construction guidance for structure and envelope and energy efficient technologies.
There are many technologies and strategies for making HVAC systems more efficient. In addition to upgrading systems, proper operations and maintenance is essential for optimal performance. The HVAC system overview page provides information on a range of strategies for increasing the efficiency of the major components of a building HVAC system, which can include boilers, chillers, cooling towers, pumps and fans, as well as sensors and controls. Heat pumps, which transfer heat rather than generating it, are an energy-efficient alternative to furnaces and air conditioners. Energy and heat recovery systems can provide substantial savings by capturing and reusing waste heat and energy. Learn more about HVAC systems and energy efficient technologies using these resources:
Energystar.gov | ENERGY STAR Energy Efficient Products
Energy.gov | Search for Energy-Efficient Products
NREL.gov | HVAC Resource Map Commercial HVAC
NHSaves.com | Commercial HVAC: 15 Energy-Saving Technologies
As the electric grid evolves from a one-way fossil fuel-based structure to a more complex multi-directional system encompassing numerous distributed energy generation sources the predictability of supply and variability of cost can introduce uncertainty, and energy storage becomes more important and valuable. The capability to store energy allows building operators increased demand flexibility, an essential component of grid-interactive efficient buildings. That is, when you can store energy, you can control the level and timing of when you use energy or return it to the grid. This allows for:
Electrifying hot water systems with heat pump water heaters, which transfer heat rather than generating it, can significantly improve energy efficiency over conventional water heaters. Additional strategies to reduce energy consumption in domestic water heating systems include:
The first step a building professional should take to improve energy management is maximizing the building’s energy efficiency. This critical step saves money, reduces the amount of energy and hence size and cost of equipment that is needed, and makes future energy management strategies easier and often less expensive to deploy. Some of the most effective efficiency measures are passive, i.e., a product of the building’s siting and structure, including constructing a building envelope that is air-tight and has thermal mass capable of absorbing heat from sunlight during the heating season and heat from warm air during the cooling season. Properly orienting the building to make optimal use of the sun’s warmth, light and energy-producing capability has a big impact on how much energy is consumed.
Active efficiency measures are those that involve designing and operating building systems and equipment to perform more efficiently. Among building systems, space heating accounted for close to one-third of end-use consumption in U.S. commercial buildings in 2018.1 Other energy-intensive building systems include ventilation, lighting, cooling and water heating. There are an ever-increasing number of technologies and strategies to optimize the efficiency of all of these systems, as well as building controls and energy management systems to ensure they all work together as efficiently as possible.
In addition to building systems, a building professional must be aware of plug loads, the often increasing amount of energy used by plugged-in equipment, from computers to video screens, and process loads, the energy used by systems hardwired into a building structure, such as elevators, enterprise servers, and commercial kitchen equipment. Plug loads are projected to continue to be one of the fastest-growing uses of energy in buildings in the coming decades.2
Read image text descriptionFor all building equipment and fixtures, opt for ENERGY STAR certified products and/or FEMP designated products wherever possible.
Energy efficiency is a complex topic because it involves optimization and interaction among multiple building systems. Upgrades and replacements must also be planned and conducted thoughtfully to avoid negative impacts on occupant health, comfort or job performance.
For all buildings systems and equipment, regular maintenance is essential.
Energy modeling is the process of using computer-generated calculations or simulations to estimate a project’s anticipated energy use impact. Energy modeling can enable the comparison of a building’s projected energy use to a baseline performance case and inform energy efficient building and system design decisions. Use DOE EnergyPlus to obtain a whole building energy modeling simulation.
Building commissioning is a process of verifying and documenting that the facility and all of its systems and assemblies are planned, designed, installed, tested, operated, and maintained to meet the owner’s project requirements. This means testing all systems, such as HVAC, lighting, and domestic water heating systems, to ensure they function as intended. Proper commissioning saves energy, reduces risk, and creates value for building operators. It also serves as a quality assurance process for enhancing the delivery of the project.
Retro-commissioning is commissioning of a building that has never been or was not fully commissioned at its completion. It includes developing a building operation plan that identifies current operating requirements and needs, conducting tests to determine whether building systems are performing optimally in accordance with the plan, and making any necessary repairs or changes.
Short of full retro-commissioning, building re-tuning is a systematic process to identify operational problems by leveraging data collected from a building automation system and correcting those problems at no-cost or low-cost. Learn more about re-tuning from the Pacific Northwest National Lab.
Monitoring-based commissioning, when implemented with an energy management information system [PDF] that monitors, analyzes, and controls building energy use, enables building engineers and facility or energy managers to continuously track whether energy savings have persisted and to find additional opportunities for improved system performance.
Deep energy retrofits renovate buildings to reduce site energy use by at least 40% using an integrative and whole-systems approach that combines bundles of energy conservation measures rather than considering individual technologies in isolation. Though often more expensive upfront, deep energy retrofits tend to deliver substantially greater value than piecemeal solutions. For several years, GSA has demonstrated the value of using energy savings performance contracts and utility energy service contracts to achieve deep energy retrofits.
Renewable energy comes from sources that are either inexhaustible or can be replaced very rapidly through natural processes. Examples include the sun, wind, geothermal energy, small hydropower such as river turbines, and other hydrokinetic energy such as waves and tides.
Using energy generated from renewable sources has a range of benefits. It mitigates pollutant emissions, reduces U.S. dependence on foreign energy sources, and onsite renewable energy increases federal energy security by reducing facility reliance on an electricity grid. Renewable energy tends to provide long-term price stability, as it does not depend on costly and/or price-variable fuel sources. At the same time, some renewable energy sources, such as sun and wind, are ‘variable’ or ‘intermittent’, meaning the supply is not consistent. There also may be a mismatch between when and where renewable energy is most efficiently produced vs. where and when it is needed most. These challenges can be addressed through energy storage in batteries and building and grid integration.
HVAC systems are typically the biggest users of energy in public and commercial buildings. According to the DOE Commercial Building Energy Consumption Survey (CBECs) [PDF], in 2018, space heating constituted at least two-thirds of commercial building consumption for natural gas, district heat, and fuel oil. The next most common uses, depending on building type, are domestic water heating and cooking.
For the upgrade of HVAC systems to more efficient models, heat pumps are a popular solution. These systems use electricity to transfer heat rather than generate it and are classified by their thermal energy source. Air-source heat pumps work by drawing thermal energy from the air, while geothermal or ground-source heat pumps rely on the relatively constant temperature underground, and water-source heat pumps employ a water source. Heat pumps are also characterized by their thermal distribution method, e.g., air-to-air heat pumps use air to circulate heat throughout a building, while air-to-water or hydronic heat pumps use water for circulation purposes. Variable refrigerant flow systems use refrigerants as the circulating medium.
While air-source heat pump performance has traditionally been diminished in the coldest climates, cold climate heat pump performance continues to improve. HVAC systems typical for large buildings, including those relying on boilers and distributed heating systems, can make cost-effective system modernization challenging. Get training on buying heat pumps.
Consider upgrading domestic water heating systems: heat pump hot water heaters use a third or less energy than traditional electric water heaters since they transfer heat instead of generating it.
An increasing number of local and state governments are starting to adopt building performance standards, which are outcome-based policies aimed at reducing the emissions of the built environment by requiring existing buildings to meet energy performance targets. The National Building Performance Standards Coalition brings these jurisdictions together to learn from each other.
DOE Building Technologies Office coined the term grid-interactive efficient buildings (GEBs), uniting the goals of building energy efficiency and building and grid integration into one suite of strategies. GEBs build on the well-established discipline of energy efficiency by adding strategies and technologies to also manage peak demand and coordinate buildings’ electrical loads, taking into account peak usage hours, generation mix, storage options, and resiliency needs as appropriate. Efficient appliances, equipment, and whole building energy optimization reduce both overall energy consumption and peak demand.
Explore a case study showing GSA applying GEB concepts to a building project.
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The Wayne Aspinall Federal Building is a case study for minimizing energy use. Originally constructed in 1918, renovations successfully converted the building into a model of energy efficiency, while preserving its original character. Energy objectives are met through a combination of high-performance, energy efficient materials and systems, and on-site renewable energy generation. As a result of the upgrades, the building is now 50% more energy efficient than a typical office building. On-site renewable energy generation is intended to produce 100% of the facility’s energy needs throughout the year. Energy efficiency features include variable refrigerant flow for the HVAC, a geo-exchange system, advanced metering and building controls, high-efficient lighting systems, a thermally enhanced building envelope, interior window systems which maintain the historic windows but increase thermal performance, and advanced power strips with desk mounted individual occupancy sensors. Renewable energy is provided by 385 photovoltaic roof panels that generate enough power to meet the electricity needs of 15 average American homes or 123 kw.
The R.W. Kern Center demonstrates techniques to reduce energy use. In addition to passive solar orientation, an air-tight envelope, and triple-glazed windows to help mitigate against large swings in temperature and humidity, the double-stud cavity wall and roof are filled with cellulose insulation to achieve assembly values of R-40 and R-60, respectively. An inverter-driven heat pump system provides heating and cooling to the spaces, separate from the heat recovery ventilation system. By reducing the building’s design energy use, a 118 kW rooftop solar array can generate more than enough energy on an annual basis. Wood is the major structural material and unnecessary finishes were rejected to conserve funds for high-impact, high-performance components, like the triple-glazed windows and insulation.
The Phipps Center for Sustainable Landscapes is a case study for minimizing energy use. Passive-first strategies are coupled with high-performance technologies to permit the downsized mechanical system—a custom-built rooftop energy recovery unit—to operate as efficiently as possible. The long, relatively narrow building sits on an east-west axis, which allows for maximizing southern exposure. High-performance glazing on the north and south facades permits solar gain in the cold months, while louvers and strategic deciduous tree plantings prevent unwanted heat gain and glare in the warm months. Computational fluid dynamics studies determined placement for BAS- and occupant-controlled windows to maximize natural ventilation. Daylighting is maximized with light shelves and sloped ceilings to direct natural light into the interior and energy use is monitored by the individual plug, which permits any anomalies to be addressed. Occupants each have electricity meters at their desks to encourage energy-saving behaviors. Energy is produced onsite via a vertical-axis wind turbine and a 125kW photovoltaic array. The atrium, constructed of concrete with recycled fly ash, acts as thermal mass, increasing energy efficiency.
The Chesapeake Bay Brook Environmental Center is a case study for minimizing energy use. Conservation strategies were organized into passive and active approaches. The building was designed to maximize diffused daylighting from the north while shielding the building interior from direct sunlight from the south and a photosensor dimming-control system was used in almost every space to reduce electric lighting when sufficient daylight is present. Windows and even walls were designed to open up and take advantage of the natural breezes prevalent near the Chesapeake Bay and the mechanical system uses a variable-refrigerant flow system with geothermal wells. Two 10-kW wind turbines, each on a 70-ft pole, are located off the east and west ends of the building, as far away as possible from nearby trees, but close enough to limit site disturbances. A solar photovoltaic system, consisting of 141 270-W modules for a total of 40 kWp, is located on the sloped roof and 6.5 kW of additional photovoltaic modules were added after the completion of construction.
1 EIA.gov | 2018 Commercial Buildings Energy Consumption Survey, Consumption and Expenditures Highlights [PDF]
2 NREL.gov | Office Buildings: Assessing and Reducing Plug Loads in Office Buildings [PDF]
U.S. General Services Administration
