Why Open Data Standards Matter for Home Performance

December 10, 2018
Winter 2018
A version of this article appears in the Winter 2018 issue of Home Energy Magazine.
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Utility and state program administrators have long used proprietary software and communication protocols to manage and process data collected by home performance contractors. This has typically resulted in higher costs of doing business (for programs and contractors), vendor lock-in, and less-efficient management processes, especially if the data were not standardized. It has also greatly limited the ability to track and aggregate energy savings across programs and states, because data are being collected in different formats and are not easily exchangeable. In larger programs that serve hundreds of homes per year, thousands of data points may be collected, representing a significant cost to the industry if data cannot be easily aggregated, shared, and analyzed. Without data standardization, administration tasks such as verifying, sharing, and processing data become costly and labor intensive.


Home Performance Extensible Markup Language, or HPXML, was created to make data collection and reporting more efficient and less expensive for industry stakeholders (see Figure 1). It does this through a combination of two related data standards published by BPI. Standard BPI-2200 is a data dictionary, which standardizes the names, definitions, and data formats for terms used to describe a home’s energy efficiency features, systems, and performance. Standard BPI-2100 specifies a standard extensible markup language that enables different software systems to exchange information at the click of a button. The industry uses HPXML to make data more meaningful and interoperable, and by extension, more accessible to the market actors that benefit from the use of residential building and performance data.


Figure 1. HPXML was created to make data collection and reporting more efficient and less expensive. Note: This graphic is designed to illustrate some of the potential ways that HPXML can assist the market. However, not all connection or impacts of HPXML could be captured in this illustration.

HPXML is an open standard because it can be freely accessed, adopted, and improved upon. Like other open standards, HPXML facilitates broad industry adoption because it eliminates one of the biggest barriers to adoption—the cost of obtaining and using the standard. Open standards give everyone access to the standard’s definitions and protocols so that use of the standard does not require interpretation or transformation, nor does it lock the customer into a particular vendor. This creates a fair, competitive market for implementations of the standard.

Another important attribute of open standards is that they are developed through an open, consensus-based process that does not allow one organization to gain a competitive advantage over its competitors. The Home Performance Coalition chairs the HPXML Working Group with oversight from the BPI Data and Modeling Standard Technical Committee. The working group consists of 60 member companies, including software developers, contractors, utilities, government, nonprofit organizations, and others that are using HPXML and are invested in its development. Any person or organization may submit a request to change or enhance HPXML. These requests go through a review and approval process established by BPI to ensure that decisions about the development of the standard is collaborative and consensus based. Because people with diverse backgrounds and goals are invited to participate in the creation and use of HPXML, the standard, like other open standards, represents the best solution for our industry.

Home energy efficiency programs that have adopted HPXML-compliant software have saved time and money by automating project review and quality assurance processes. Many have also been able to open the software market for home performance contractors. For example, one year after implementing HPXML, Arizona Public Service (APS) decreased its quality assurance administrative labor by 50%. Contractors working with APS also decreased administrative labor per project by 31% after the implementation of an HPXML software environment.

The National Renewable Energy Laboratory (NREL) has also used HPXML to increase data consistency across DOE and industry programs. The lab is currently developing an open EnergyPlus-based residential energy-modeling platform for DOE’s Home Energy Score (HEScore), Weatherization Assistant auditing software, and an energy-rating index—a project that harmonizes the calculations of HEScore and HERS (see Figure 2). This work, when completed next fall, is expected to accelerate new software applications (particularly those related to scoring and certifying energy-efficient homes), and to lower the industrywide costs of maintaining multiple simulation engines, says NREL’s Research Engineer Noel Merket.

Figure 2. NREL is considering developing an open EnergyPlus-based residential energy-modeling platform for DOE’s Home Energy Score (HEScore), Weatherization Assistant auditing software, and an energy-rating index—a project that harmonizes the calculations of HEScore and HERS.

learn more

Get more information about HPXML.

Read about the HPXML Working Group.

See a list of programs that have adopted HPXML.

Get more information on the APS program.

Read Noel Merket’s blog post on the NREL project.

Connection, transparency, and data standardization are crucial for innovation and for building markets. If we want to scale the residential energy efficiency industry, utilities, contractors, government, and other private sector actors will need to be connected to each other and to stakeholders in other industries, such as the financial and real estate markets. The market will also need to have access to high-quality, low-cost data on residential buildings, energy conservation measures, and energy performance.

The most efficient and cost-effective method for achieving these goals is to support the development and adoption of HPXML. Every time a program requires use of HPXML, transactional costs fall for organizations already using the standard. Software vendors can provide a rich set of data about an energy efficiency upgrade to program administrators using HPXML at very little additional cost, because they have already made the initial investment to follow the standard. It is crucial, however, that more organizations adopt the standard to ensure that the potential benefits of HPXML are fully realized by the residential energy efficiency industry.

Julie Caracino is Director of Research and Standards at the Home Performance Coalition.

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