Tools and ideas to power the future of low energy buildings


If you ask the wrong question ... you will get the wrong answer. It's much more important and difficult to ask the right question. Once you do that, the right answer becomes obvious. 

- Amory Lovins

About Us

Vistar Energy is a consulting firm that provides expertise and knowledge in the field of building energy efficiency. Our goal is to ask the right questions and develop the right solutions to face the challenges of building a future with low (and zero) energy buildings.

Mudit Saxena is the founder and principal of Vistar Energy. He has over 14 years of experience in building energy consulting. He has helped clients overcome critical technical barriers through research, software development and training, to develop and promote energy efficiency programs and strategies. He is an internationally recognized expert in daylighting and lighting research, and his work has led to development of various building energy codes and standards such as LEED v4, Title-24, and ASHRAE 90.1.




 Mudit Saxena
 Principal and Founder

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The purpose of computing is insight, not numbers.
— Richard Hamming


With advances in technology and design, buildings today can transition from being reckless resource users to "smart energy consumers" – using only what is needed, only when appropriate. The best systems and technologies can also improve the architectural and environmental quality of the spaces while optimizing energy performance. However, to realize this potential in buildings at a large scale will require a concerted effort on many different fronts. From new and creative tools to help design and implement energy efficiency improvements; to better building standards; to building science and human factors research.

Our goal at Vistar Energy is to help clients across the building industry achieve this potential in buildings, at a scale to meet global needs of energy and carbon reduction. In pursuit of that goal, Vistar Energy offers consulting services in these areas:

Technology Assessments and Energy Monitoring

Vistar Energy provides deep technical understanding of how building systems and technologies operate and interact with building occupants. We have experience conducting field assessments of energy performance on technologies ranging from building envelope components, to lighting and HVAC. We make sense of energy data to provide unbiased evaluations of energy efficiency technologies, and guide our clients on product improvement and strategize on emerging technology promotion. With our expertise in simulation studies we can combine field performance data with energy simulation to provide a comprehensive technology assessment.

Building Science and Human Factors Research

We are greatly committed to furthering our collective understanding of building science through research, especially as it applies to human and environmental factors. As building technologies advance, research is needed to better understand their impact on occupants, and in-turn, the impact occupant behavior on building energy-use. We bring years of experience, working with leading building scientists to develop research plans to answer the right questions for our clients and explore the most appropriate technical means to conduct research studies.

Energy Saving Calculators /
Simulation Tools Development

Vistar Energy provides the expertise and technical proficiency to conceptualize and develop innovative energy calculation tools and simulation software suited to our clients needs. These tools enable users to design buildings and estimate savings to make decisions on energy efficiency improvements. We have experience developing a range of energy calculators and simulation tools: from Excel-based energy savings calculators, to developing algorithms for use in eQUEST and EnergyPro building simulation software, to developing advanced daylighting simulation approaches with Radiance.

Strategic Market Research

We provide market research to help clients make sense of the ever changing landscape of building energy efficiency. As technologies evolve and design practices change at a rapid rate, we provide road-maps and strategic planning guides that offer crucial insights into market trends and behavior.  We bring together our experience working with many industry stakeholders, researchers and policy makers to provide a comprehensive outlook on market conditions, with the goal to consult on the best strategies to develop and promote energy efficiency.

Building Energy Modeling and Simulation Studies

Vistar Energy has detailed knowledge and experience with a vast spectrum of building energy simulation tools to provide our clients guidance on all aspects of building energy modeling. Combined with state-of-the-art tools for data visualization and data analysis, we provide insight and recommendations on design and technology options to achieve deep energy savings. 

Codes and Standards Research and Development

Vistar Energy provides technical expertise to develop research-based energy code change proposals and guide these proposals through the sometimes complex rule-making processes. We have experience successfully working with industry stakeholders, as well as state and national agencies that develop building energy codes, to implement code changes that have resulted in energy savings at the state and national scale.

Professional Training and Technical Writing

We provide well designed and thought-out training materials as well as professional training services on a variety of topics related to building energy efficiency. We have experience developing design guides, technical white-papers and delivering professional training on topics ranging from daylighting design and lighting controls to building energy simulation and code compliance.

Select Publications

This paper describes the challenges in developing energy savings estimates for utility program needs. A new calculation tool for Advanced Lighting Control Systems (ALCS Calculator) is introduced that calculates savings against dual baselines. The paper discussed key concepts of the ALCS Calculator, and the implications of developing a standard calculation methodology for the lighting controls industry.

This paper provides a technical overview of the calculation methodology developed for the Advanced Lighting Control Systems (ALCS) Calculator Tool and discusses key concepts of the tool’s calculation approach and how it differs from previously developed calculation tools for lighting controls savings.

This paper describes the results from a recent Emerging Technologies assessment study on Advanced Daylighting Blinds and Shades.

This article was published in a special edition of the Journal of the National Institute of Building Sciences on Fenestrations. The article provides a unique perspective and vision on balancing the needs for daylight, energy and indoor environmental quality through appropriate fenestration design.

This paper describes the results from the CEC PIER project that estimated the demand and energy savings potential from adding photo controls to existing office spaces in California.

This paper introduces the new approach in Radiance that allows users to model variable fenestration optics using BSDFs and permits fast, matrix-based annual daylighting calculations.

  • 61 Flavors of Daylight. American Council for an Energy-Efficient Economy (ACEEE) Summer Study. Asilomar, CA. August, 2010.

This paper describes the research effort to develop the new IES approved daylight metrics, involving a massive simulation and data collection effort from 61 buildings.

This paper discusses the variety of user needs for prediction of daylighting performance in buildings, and introduces a Daylighitng Analysis Framework to help prioritize the development of analysis tools, metrics and methods for daylighting.

This paper describes the results of a technology assessment study that evaluated performance of advanced skylights with light redirecting properties using moving mirrors and advanced optics, and compared them to the performance of traditional skylights.

Select Presentations


  • The New IES-Approved Daylight Metrics. A joint AIA San Francisco and IBPSA Webinar. October 2014 - Link to slides and presentation recording
  • Using Climate Based Daylight Metrics. A Light Affair - Symposium by IES & PG&E at the Pacific Energy Center, San Francisco, CA.  June 2014
  • Improving Daylighting Performance Prediction - New Metrics and Tools. LightShow West, Los Angeles, CA. October 2013
  • Radiance in Energy Codes and Standards. Radiance Workshop, Golden, CO. August 2013
  • Daylight, View and Windows: The Human Connection. Invited speaker at the GANA Annual Conference, San Diego, CA. January 2013
  • Opportunities for Daylight Harvesting in Existing Office Buildings. Lightfair 2012, Las Vegas, NV. May 2012
  • Windows Are For People: Optimizing Windows for Human Comfort. Building Enclosure Technology and Environment Council Symposium. Washington DC. January 2013
  • Daylighting Plans for Existing Buildings. webinar. June 2011
  • Integrating Window Treatments with Electric Lighting Strategies for Occupant Comfort and Energy Savings. Lightfair 2010, Las Vegas, NV. May 2010
  • Dynamic Window Shading Systems. Greenbuild 2008, Boston, MA. November 2008
If you can’t explain something simply, you don’t understand it well enough.
— Albert Einstein