Buildings consume approximately three-quarters of the electricity used in the United States, and account for 40% of primary energy use and corresponding greenhouse gas emissions. Given the scale of energy resources dedicated to heating, cooling, and maintaining these structures, there is a significant opportunity to achieve savings through policies promoting efficiency in existing buildings as well as in the design and construction of new buildings. Building energy codes that mandate a minimum level of energy efficiency in new buildings, benchmarking programs that help building owners and operators better understand their patterns of energy use, and transparency policies that make visible the energy consumption of buildings are just a few of the tools available to policymakers to help reduce energy waste in the building sector.
Building energy codes and standards set minimum efficiency requirements for new and renovated buildings. By establishing baseline requirements during building construction, buildings use less energy, are more comfortable, and cost less to operate. It is also easier to increase the efficiency of a building during its construction than to try and do so after the fact.
Two codes set the standard the standard for US commercial and residential building energy codes: the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1 and the International Energy Conservation Code (IECC). Each are amended on a three-year cycle during which proponents of energy efficiency can suggest and support code changes. While the IECC’s focus is primarily residential one- and two-family dwellings and small multifamily buildings, ASHRAE 90.1 sets standards for commercial and high-rise multifamily residential buildings. Building energy codes can be divided into two primary frameworks:
- Prescriptive codes assign specific minimum criteria that must be met for new building construction, such as minimum heat reflectivity (R-value) for insulation and windows, and installation and control requirements for HVAC systems.
- Performance codes are intended to provide greater flexibility to designers by reducing prescriptive requirements and setting a minimum energy performance target. Depending on the type of climate in which a building is constructed, engineers may achieve more benefit by emphasizing certain types of efficiency features over others. Software tools for modeling and compliance (like EnergyPlus, REM/Rate, REScheck, or COMcheck) can help determine the optimal combination of efficiency measures.
In addition, a variety of voluntary stretch codes, standards, and certifications have been developed to achieve different efficiency and sustainability goals. Below are some examples:
- ASHRAE 189.1 (link). A more sustainable and energy-efficient version of ASHRAE 90.1 adopted by some jurisdictions.
- LEED (link). This certification program uses holistic point-based sustainability rating systems for new buildings, existing buildings, homes, and more.
- New Buildings Institute 20% stretch code (link). Developed to achieve a 20% energy performance improvement over ASHRAE 90.1-2013 baseline code.
- Passive House Institute US Certification (link). Highlights “passive” building systems that emphasize tight building envelopes and passive solar heat/lighting to minimize energy use.
- State- and jurisdiction-specific stretch codes. States and cities have developed their own versions of stretch codes that can serve as a model for others: Massachusetts, New York, and Santa Monica are examples.
- Zero Energy Ready Home (link). Developed by the U.S. Department of Energy to identify homes that meet criteria of the DOE Zero Energy Ready Home National Program Requirements, such as containing solar-ready roofing and connections.
The value of energy efficiency in properly implemented construction standards is universally recognized as the easiest and most cost-effective way to help consumers save energy and money, make housing more affordable, and reduce air pollution. All of these benefits are difficult or impossible to capture if they are not taken into consideration at the time of construction.
When information about a building’s energy efficiency and its opportunities for improvement are readily available to potential owners, buyers, or renters, it can motivate them to select or upgrade to more efficient buildings.
Benchmarking is the practice of collecting building energy use data, tracking energy use over time, and using this data to compare a building’s energy use to that of a similar structure. When combined with transparency laws requiring this information to be shared with prospective buyers, benchmarking becomes a valuable resource to spur owners to make their buildings more efficient and help purchasers and renters make smart, energy-efficient decisions about where to live and what properties to buy.
Many states and cities have established energy benchmarking policies for publicly-owned buildings, while a smaller but growing number of jurisdictions, such as New York City, Seattle, Washington, D.C., and Boston, have adopted similar transparency policies for private sector buildings. At the national level, additional voluntary programs such as LEED and ENERGY STAR Portfolio Manager in the commercial sector and RESNET and ENERGY STAR labeling in the residential sector have also offered resources to building owners and policymakers to better track and manage energy use. In addition, efficiency advocates and government agencies at all levels have worked to devise residential energy labeling programs and policies that inform home buyers and real estate stakeholders about a home’s energy performance. Given differences in priorities among regions and stakeholders, a diverse patchwork of ratings, each with varying metrics and areas of focus, have arisen to meet the challenge. Below are some examples:
- Residential Energy Services Network (RESNET) Home Energy Rating System (HERS). Considered the industry standard, the HERS rating is required for a home to qualify for ENERGY STAR® certification, DOE Zero Energy Ready Home certification, and many energy efficiency programs that target new construction.
- US DOE Home Energy Score (HES). Launched in 2012, HES has been used primarily for existing homes. HES rates homes on a 1–10 scale, with 10 being the most efficient.
- Energy Trust of Oregon Energy Performance Score (EPS). Rating on a scale of 0 (most efficient) to 200 (least efficient), the EPS provides an estimate of monthly and annual energy costs, as well as the home’s carbon footprint, and compares these with other Oregon homes of similar size and homes built to code. While there is no requirement to score homes at the time of sale, the Multiple Listing Service for the majority of Oregon accepts and posts each of the three approved scoring systems.
- Energy Metrics to Promote Residential Energy Scorecards in States (EMPRESS). A state energy office-led initiative supported by DOE and private partners, EMPRESS aims to coordinate and harmonize the software platforms for DOE’s HES and RESNET’s HERS ratings as well as to foster voluntary use of residential energy data by real estate market stakeholders and others.
- Home Energy Labeling Information eXchange (HELIX). Led by NEEP and supported by DOE, six New England states and New York have come together to develop a database to help bridge the energy information gap between home sellers and the market by auto-populating real estate listings with verified independent home energy information from home energy labels, such as HES and HERS, and other available energy data. A final, pilot-tested system is anticipated for full-scale operation in 2019.
- Home Energy Information Accelerator. One of 13 Better Buildings Accelerators launched by DOE since 2013, the Home Energy Information Accelerator is a collaboration among national, regional, state, and local leaders aimed at expanding the availability and use of reliable home energy information in residential real estate transactions, such as through listing services and other reports. Other goals include providing data standards and technical assistance.
A select number of cities have gone beyond benchmarking and transparency to pass building performance policies that require building owners to act on energy use information collected through benchmarking.
Places like New York City, Seattle, and Boulder have passed laws requiring owners of existing buildings to make efficiency improvements like upgrading their lighting to systems required under current building energy codes or implementing all recommended energy conservation measures from an energy audit that meets a certain payback period. Building performance efforts seek to improve the energy performance of existing buildings by taking a comprehensive approach to increasing their energy efficiency, comfort, and productivity. Building performance initiatives address building systems (HVAC, lighting, etc.) as well as operations and maintenance (O&M). Common building performance services include building tune-ups, retrocommissioning, comprehensive building assessments, and retrofits. SmarterHouse, an online guide run by ACEEE, is a helpful resource for homeowners seeking to reduce their energy use by making their homes more efficient, tightening the building shell, or selecting more efficient products including appliances, heating equipment, air conditioning, lighting, and electronics.
Building modeling and simulation is a growing discipline. Modeling software can be used to estimate a building’s projected energy and water use, as well as building performance, during the design phase of construction. Modeling can also be done for research purposes: for modeling the effects of solar technologies, emerging technologies, etc.
There are many different software packages available: free versions, versions for commercial and residential buildings, and end-use-specific software (e.g. HVAC or solar modeling). More information about building energy modeling and available software tools can be found below:
- DOE: Building Energy Modeling.
- Rocky Mountain Institute. 2013. Building Energy Modeling for Owners and Managers: A Guide to Specifying and Securing Services.
- International Building Performance Simulation Association (IBPSA-USA). Building Energy Software Tools.