New Building Energy Simulation Tool for Residential Retrofits May Simplify Reach Code Development
With single-family residential buildings representing more than 60% of total U.S. building stock and 47% of energy consumption (RECS 2015, CBECS 2012), more and more local jurisdictions are evaluating how to incorporate energy efficiency goals for existing residential buildings into their Climate Action Plans and reach codes. As the City of Chula Vista story in this issue illustrates, there are many variables to consider, and one significant challenge is how to quantify the expected benefit from specific measures.
A new building energy simulation tool called XeroHome,™ developed by Vistar Energy, offers promising capabilities. XeroHome was developed under a Small Business Innovation Research grant from the U.S. Department of Energy (DOE-SBIR). An energy modeling platform capable of modeling single-family homes at scale, XeroHome analyzes multiple individual homes while capturing each home’s size, vintage, permit history, geometry, site orientation, fuel type and utility rates. This enables the analysis to capture the diverse range of home energy performance and savings potential not possible with a single home prototype approach. The tool can develop an ‘opportunity map’ for an entire region, with models that predict energy and carbon savings from specific energy efficiency measures or combinations of measures.
“Using machine learning and surrogate modeling, the tool is able to significantly speed the process of running multiple models,” notes Mudit Saxena, CEO of XeroHome. “We see this tool as a promising one for cities who are contemplating specific reach code measures for existing homes but lack the resources to conduct this kind of research themselves.”
The company recently conducted feasibility studies for eight cities, each over 50,000 residents, located across the state. The project, funded by Southern California Edison’s (SCE) Codes and Standards Program, focused on two specific measures: replacing a gas water heater with an electric heat pump water heater and rooftop solar. In many cases, requiring the water heater replacement alone proved not to be cost-effective in most jurisdictions. However, by bundling the two measures, the modeling showed cost-effectiveness for seven of the eight jurisdictions studied. This bundling approach can be a way to promote electrification in regions where utility rates and upgrade economics make it particularly challenging for homeowners. The modeling methodology was conservative, for example, the modeling assumed full cost of replacement and did not include current utility rebates except the solar federal tax credit.
“With this type of analysis,” suggests Peter May-Ostendorp, CTO of XeroHome, “local jurisdictions can fine-tune specific measures and identify the optimal bundles for their communities, taking into account climate, utility rates, home vintages, an entire range of variables.”
On the individual homeowner level, the tool provides homeowners with an energy upgrade plan over a simple website, uniquely customized for their home with clear recommendations for cost-effective, clean energy options. Homeowners are supported all the way from decision making to finding a contractor in their region to installing the upgrade, all from within the XeroHome tool interface. SCE’s Reach Code and Emerging Products and Technology teams are partnering with the City of Santa Monica to assess the accuracy of the XeroHome tool by comparing on-site energy audit results with the XeroHome energy modeling outputs. Additionally, this project also analyzes the effectiveness of the tool in engaging homeowners to install energy efficiency equipment. For more information on this project, email Christopher Kuch.
For general information, visit XeroHome.