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Residential Buildings Research Staff

Members of the Residential Buildings research staff have backgrounds in architectural, civil, electrical, environmental, and mechanical engineering, as well as environmental design and physics.

Photo of Kyri Baker

Kyri Baker — Engineer

Ph.D. Electrical and Computer Engineering, Carnegie Mellon University
M.S. Electrical and Computer Engineering, Carnegie Mellon University
B.S. Electrical and Computer Engineering, Carnegie Mellon University

Kyri joined NREL in 2015. Her current work focuses on distributed control of power distribution systems, optimal residential building control, and PV hosting capacity analysis. Her previous research focused on distributed optimization of transmission grids for the integration of renewable resources, along with model predictive control and optimal storage planning and operations under uncertainty.

Contact information:, 303-275-3190

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Photo of Chuck Booten

Chuck Booten — Senior Engineer

Ph.D. Mechanical Engineering, Stanford University
M.S. Mechanical Engineering, Massachusetts Institute of Technology
B.S. Mechanical Engineering, Massachusetts Institute of Technology

Chuck joined NREL in 2010. His research is focused on heat transfer modeling, heating, ventilating, and air conditioning (HVAC) system analysis and testing, and the study of grid-connected homes.

Prior to working at NREL, Chuck was a project manager at Protonex Technology, where he directed the development of kilowatt-scale solid-oxide fuel cell systems for both military and civilian customers. His background is in experimental heat transfer and fluid mechanics.

Contact information:, 303-275-3167

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Photo of Craig Christensen

Craig Christensen — Principal Engineer

M.S. Mechanical Engineering, Brigham Young University
B.S. Mechanical Engineering, Brigham Young University

Craig joined NREL in 1979. He currently leads the energy analysis efforts for the Building America Program and supports solar buildings research efforts at NREL that includes BEopt development, analysis for new and existing residential buildings, and modeling accuracy. Craig has also led many projects related to residential and commercial buildings, active solar systems, passive solar design, energy conservation, and computer modeling of buildings, systems, and components. He originated the concept of the unglazed transpired solar collector at NREL and participated in research that led to an R&D 100 Award and Popular Science "Best of What's New" Award in 1994.

Prior to joining NREL, Craig worked as a solar consultant, individually and at a small mechanical engineering firm. He also worked for three years for the National Oceanic and Atmospheric Administration as a scientist and officer on oceanographic ships.

Contact information:, 303-384-7510

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Photo of Dane Christensen

Dane Christensen — Senior Engineer

Ph.D. Mechanical Engineering, University of California-Berkeley
B.S. Mechanical Engineering, Rice University

Dane joined NREL in 2008 with a background in equipment testing and integration. He manages the Residential Building Group’s laboratory work and coordinates research on advanced HVAC systems. This work addresses technology gaps for healthy, durable, and energy-efficient homes and provides data to improve high-performance building simulation. Dane supports technical efforts for the Building America Program and conducts finite element modeling for building energy simulation.

Prior to joining NREL, Dane worked at Atec, Inc. designing test and support equipment for turboshaft engines.

Contact information:, 303-384-7437

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Photo of Lieko Earle

Lieko Earle — Senior Engineer

Ph.D. Physics, University of Colorado at Boulder
B.S. Physics, Brown University

Lieko joined NREL in 2009. She leads the field testing efforts for the Building America Program. Her research focuses on developing field testing and analysis methods to identify gaps and barriers for emerging and advanced retrofit systems to be implemented on a broad basis, as well as field evaluations of innovative building envelopes, water heating, and HVAC systems. She also conducts laboratory- and field-based investigations of automated home energy management (AHEM) devices, Non-Intrusive Load Monitoring (NILM) techniques, and control strategies to develop cost-effective systems that integrate smoothly with home area networks and smart grids to maximize source energy savings.

Lieko's background is in astrophysics instrumentation and extragalactic spectroscopy. Prior to graduate school she taught physics as a Peace Corps volunteer in Tanzania, where she spent many happy hours devising laboratory experiments for students using locally available materials.

Contact information:, 303-275-4355

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Photo of Mike Heaney

Mike Heaney — Research Analyst

Ph.D. Chemical Engineering, University of Colorado at Boulder
M.S. Chemical Engineering, University of Colorado at Boulder
B.S. Chemical Engineering with Honors, Montana State University

Mike joined NREL in 2011. He currently supports projects in both the Residential Buildings Group and the Commercial Buildings Group where advanced statistical analysis is needed. Some recent projects required quantifying the impact of energy efficiency measures in retrofits, optimizing prediction models used for estimating total energy saved during demand response events, and developing models for classifying building HVAC equipment faults.

Prior to joining NREL, Mike worked at various positions requiring extensive use of advanced statistical methods applied to many technical problems. He first learned and applied a variety of statistical methods to improving laboratory measurements and chemical processes during his 11 years working for The Dow Chemical Company. Over the years, he has gained extensive knowledge and experience applying statistical methods such as classification methods, regression methods, hypothesis testing, multivariate statistical analysis (MSA), statistical process control (SPC), and statistical design of experiments (DOE).

Contact information:, 303-275-3883

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Photo of Scott Horowitz

Scott Horowitz — Senior Engineer

M.S. Civil Engineering, University of Colorado at Boulder
B.S. Mechanical Engineering, Rutgers University

Scott joined NREL in 2007 and manages the Residential Building Group's tools and analysis area, which includes work on whole building energy modeling, cost-based optimization, model accuracy/calibration, and technology assessments. He is the lead developer of BEopt, a residential building energy optimization tool used to provide support for the Building America program's teams and energy efficiency goals, and leads efforts to incorporate residential models and capabilities into DOE's EnergyPlus and OpenStudio platform.

Prior to joining NREL full time, Scott spent four years at NREL as a University of Colorado graduate student exploring enhancements to building optimization in terms of robustness and speed, and he was a member of the 1st place University of Colorado Solar Decathlon team.

Contact information:, 303-384-7560

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Photo of Xin Jin

Xin Jin — Controls Engineer

Ph.D. Mechanical Engineering, Pennsylvania State University
M.S. Electrical Engineering, Pennsylvania State University
M.S. Mechanical Engineering, Pennsylvania State University
B.S. Mechanical Engineering, Shanghai Jiao Tong University, China

Xin Jin joined NREL in 2012. His research focuses on control systems, fault detection and diagnosis, load monitoring and disaggregation, and grid-integrated building systems. Xin's background is in sensors and controls, machine learning, and embedded systems.

Prior to his current position at NREL, Xin worked as a project engineer at A.O. Smith Corporate Technology Center creating innovative electronic control solutions for water heaters and was a postdoctoral researcher at NREL developing automated home energy management technologies.

Contact information:, 303-275-4360

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Photo of Jeff Maguire

Jeff Maguire — Engineer

M.S. Mechanical Engineering, University of Colorado at Boulder
B.S. Mechanical Engineering, Rensselaer Polytechnic Institute

Jeff joined NREL in 2012 after working as a graduate student since 2010. His research focuses on the modeling and performance analysis of residential water heaters, analyzing data from field test studies of several water heaters, developing models of new water heating technologies, and performing simulations to determine the impact of use and climate on water heater efficiency. Jeff specializes in component modeling and performance analysis.

Contact information:, 303-275-4309

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Photo of Noel Merket

Noel Merket — Engineer

M.S. Mechanical Engineering, Utah State University
B.S. Mechanical Engineering, Utah State University

Noel joined NREL in 2010. He leads the residential building development of the EnergyPlus building energy simulation software. He also develops and maintains the Home Performance XML data transfer standard and supports its adoption in the industry. His prior research experience was on two-phase liquid vapor heat transfer for thermal management of small satellites.

Contact information:, 303-275-3156

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Photo of Tim Merrigan

Tim Merrigan — Senior Project Leader

M.S. Mechanical Engineering, University of Central Florida
B.S. Mechanical Engineering, Columbia University
B.A. Physics, Rollins College

Tim joined NREL in 1999. His research focuses on building-integrated renewables, solar water heating technology development, PV/thermal system development, and integrated solar heating and cooling systems.

Prior to joining NREL, Tim was with the Florida Solar Energy Center for 20 years, conducting research in solar thermal systems and building energy efficiency. Tim served as the chair of the ASHRAE Technical Committee for Solar Energy Utilization, served as the chair of the Standards Committee for the Solar Rating & Certification Corporation (SRCC), and was on the Board of Directors for the Colorado Solar Energy Industries Association (COSEIA).

Contact information:, 303-384-7349

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Photo of Lucas Phillips

Lucas Phillips — Research Technician

M.S. Technology Management, Eastern Illinois University
B.S. Organizational and Professional Development, Eastern Illinois University
A.S. Electrical Science, Community College of the Air Force

Lucas joined NREL in 2014. His efforts are focused on performing testing of emerging technologies in building efficiencies. Lucas contributes to research efforts by designing, building, and implementing testing equipment as needed to support research.

Prior to joining NREL, Lucas was involved in the design and development of curriculum and research in sustainable technologies at Eastern Illinois University: School of Technology as a Presidential Graduate Assistant. In addition, he spent eight years in the United States Air Force where he worked in communication technologies. He also has a certificate in Fiber Optics and Communication Infrastructure Installation.

Contact information:, 303-384-6482

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Photo of Ben Polly

Ben Polly — Building Energy Research Engineer

M.S. Engineering Mechanics, University of Nebraska-Lincoln
B.S. Mechanical Engineering, University of Nebraska-Lincoln

Ben joined NREL in 2009. He specializes in the development, validation, and application of energy analysis approaches for individual buildings and collections of buildings. He has developed and applied software testing approaches for residential audit tools and associated utility bill calibration methods, methods for calculating life-cycle-cost-optimal retrofit packages, and approaches for analyzing measured energy consumption to estimate retrofit energy savings and improve software prediction accuracy. Ben's current research interests also include net zero buildings and neighborhoods, urban energy design and optimization, inverse design of buildings systems and materials, and smart grid-enabling building technologies (e.g., building energy storage).

In addition to his work at NREL, Ben serves on the Building Performance Institute (BPI) Data & Modeling Standards Technical Committee (STC) and several industry working groups for BPI and the Residential Energy Services Network (RESNET).

Prior to joining NREL, Ben's graduate research focused on nanoscale material characterization, biomechanics, vibrations, and continuum mechanics.

Contact information:, 303-384-7429

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Photo of David Roberts

David Roberts — Group Manager and Senior Engineer

M.S. Civil Engineering, University of Colorado
B.S. Environmental Resources Engineering, Humboldt State University

David joined NREL in 2008. David is the Residential Buildings Research Group Manager. He supports DOE research activities including the Building America program.

David has been working in the area of energy efficiency in buildings since 1989 and is a licensed Professional Engineer in Colorado. He has expertise in building science, building energy simulation, and software development. Prior to joining NREL, David worked for Architectural Energy Corporation, where he led energy simulation and software development projects, and served as product manager for the REM/Rate™ home energy rating software.

Contact information:, 303-384-7496

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Photo of Joseph Robertson

Joseph Robertson — Engineer

M.S. Computational and Applied Mathematics, Colorado School of Mines
B.S. Mathematics/Spanish, Marquette University

Joe joined NREL in 2012. His research activities include automated building model calibration and the Field Data Repository. He specializes in building energy simulation, modeling and data analysis, and mathematical optimization.

Joe also worked at NREL for two years as an intern and graduate student from the Colorado School of Mines on projects involving numerical methods applied to uncertainty/sensitivity analysis and automated building model calibration.

Contact information:, 303-275-4575

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Photo of Stacey Rothgeb

Stacey Rothgeb — Senior Engineer/Section Manager

B.S. Architectural Engineering, Kansas State University

Stacey joined NREL in 2009. She has a diverse background in engineering design, construction project management, and energy consulting. Stacey provides technical leadership and research management for the Building America Program. Her research efforts include performance testing and analysis for both new and existing homes.

Prior to joining NREL, Stacey worked as the energy manager at the U.S. Air Force Academy. She also owned and operated her own residential energy consulting firm. Stacey is a licensed Professional Engineer (PE) and a Certified Energy Manager (CEM).

Contact information:, 303-275-4361

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Photo of Bethany Sparn

Bethany Sparn — Engineer

M.S. Mechanical Engineering, Colorado State University
B.S. Mechanical Engineering, Columbia University
B.S. Physics and Mathematics, University of Puget Sound

Bethany joined NREL in 2010. Her research focuses on connected building loads, residential HVAC equipment, heat pump water heaters, automated home energy management devices, and whole-house performance field testing. She has supported the design and build-out of the Smart Power Laboratory in the Energy Systems Integration Facility which provides a test bed for evaluating home energy management systems, demand response strategies, distributed energy resources, smart appliances, and other innovative sensors and controllers.

Contact information:, 303-384-7442

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Eric Wilson

Eric Wilson — Engineer

M.S. Civil Environmental and Architectural Engineering, University of Colorado
B.S. General Engineering, University of Illinois

Eric joined NREL in 2010. His recent activities include developing multifamily modeling capabilities for the BEopt building energy optimization software, developing an analysis framework and data visualization for national residential building stock models, and leading updates of the Building America House Simulation Protocols.

Prior to joining NREL, Eric researched the energy implications of pressure drop in residential duct systems. He also performed energy audits and design assistance for a state energy program and conducted blower door tests on tribal housing across the country.

Contact information:, 303-275-4676

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Jon Winkler

Jon Winkler — Senior Engineer

Ph.D. Mechanical Engineering, University of Maryland
B.S. Integrated Science and Technology, James Madison University

Jon joined NREL in 2009. His research focuses on residential HVAC systems, residential dehumidification control, energy modeling tools, and BEopt development.

Prior to working at NREL, Jon was a faculty research assistant in the Mechanical Engineering Department at the University of Maryland, where he co-led the development effort of simulation and optimization software used by HVAC manufacturers.

Contact information:, 303-275-4356

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Jason Woods

Jason Woods — Senior Engineer

Ph.D. Mechanical Engineering, University of Colorado
B.S. Mechanical Engineering, Purdue University

Jason joined NREL in 2010 after working there as a doctoral student since 2007. Jason's expertise is heat and mass transfer, including the design, analysis, and testing of devices and processes. Some research areas include: (1) innovative HVAC technologies, using techniques such as liquid desiccant dehumidification, evaporative cooling, and membrane-based processes, (2) combined cooling, heat, and power (CCHP) systems, and (3) moisture storage and transport in building materials.

Contact information:, 303-384-6189

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Support Staff

Jason Woods

Marcia Fratello — Administrative Associate

Marcia joined NREL in 1999. She supports the group manager, engineers, and researchers in the Residential Buildings Research Group and Building America Program. Prior to joining NREL, Marcia worked as an administrative assistant for more than 25 years at various levels for both small and large companies including American Cyanamid and Johns Manville.

Contact information:, 303-384-7440

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Kristy Usnick

Kristy Usnick — Project Administrative Associate

Colorado Mountain College/Pueblo Community College, Business Management
US NAVY Telecommunications Certified

Kristy joined NREL in 2011. She supports the Building America research coordinator team as well as the engineers and researchers in the Residential Buildings Research Group. She is the site administrator for the internal and external SharePoint sites, system administrator for the Editorial Manager National Renewable Energy Laboratory Peer Review System, and manages the Residential Buildings publications in PubHub.

Prior to joining NREL, Kristy worked as an environmental/radiation safety administrative assistant for more than 11 years at a Uranium Milling Facility in Southern Colorado.

Contact information:, 303-384-7448

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