Net Zero Energy Buildings: Achieving the Art of the Possible
Net zero energy buildings are emerging as a trend of the future – in the 2013 Energy Efficiency Indicator survey, over 70 percent of respondents said they intend to achieve zero, near zero, or positive energy status for at least one of their buildings in the future. Net zero energy buildings demonstrate the art of the possible for energy efficiency and renewable energy while communicating that the building owner and occupants are environmental champions. Whether for new buildings, existing buildings, or communities, achieving net zero energy status means first maximizing energy efficiency, then adding renewable generation to cover remaining energy demand.
The Institute for Building Efficiency has completed a series of issue briefs on Net Zero energy buildings:
Definitions and case studies (Absolute Zero. Net Zero Energy commercial buildings - an inspiring vision for today, 11/2007
The opportunity and drivers (Net Zero Energy: Technologies and approaches to Transform the Built Environment, An Overview, 4/2012)
Lessons from Early Adopters (The Move Toward Net Zero Energy Buildings. Experiences and Lessons from Early Adopters, 8/2012)
Existing buildings (Reinventing Existing Buildings: Eight Steps to Net Zero Energy, 5/2013)
Communities (Net Zero Communities: One Building at a Time, 8/2012)
Definitions and Case Studies
Our first issue brief in the series discusses the net-zero energy building concept and definitions, examines common features demonstrated by net zero buildings, briefly reviews the policy context that will make such buildings increasingly common, and presents case studies of the eight known commercial net zero buildings in the U.S. as of late 2009.
The Opportunity and Drivers
Net Zero energy buildings represent a transformative shift in the built environment. As the second issue brief highlights, the technologies and innovations exist already to make net zero energy building achievable.
Lessons from Early Adopters
“Start early, seek advice, and stay engaged” were the three take-away messages from interviews with owners and net zero energy building project managers. The Institute for Building Efficiency met with those responsible for 11 new-construction and major retrofit projects to understand the motivations, the challenges, and the keys to successful projects. Among the insights:
Owners were driven by a mix of traditional motivators – cost and resource savings, occupant well-being and environmental responsibility – along with a desire to show what is possible with technology and with the right ideas and innovations.
Challenges included local regulations, skepticism about the concept, perceptions of high cost, and communication of the concept to regulators and building occupants.
Integrated design, involving multiple parties at the earliest stages, was critical.
Owners must understand the technologies and systems available, as the choices significantly affect budgets and schedules.
Creating and communicating a compelling vision around the net zero building helps to ensure buy-in from stakeholders, especially the building’s users. Occupants who become “green champions” can help buildings meet their net zero energy objectives.
Increasingly, leading owners are focusing on how to take existing buildings to net zero. The process is similar to that for a deep energy retrofit, but with some additional considerations, including:
Choosing a definition of net zero energy
Iterative modeling, design and costing of energy measures. This modeling should include both weighing the levelized costs between efficiency and renewables and an analysis of net metering, load leveling and matching generation.
Phasing installation and implementation
With the Rocky Mountain Institute, the Institute for Building Efficiency explored the process of taking an existing building to net zero and shared examples:
How can the concept of net zero energy buildings translate to net zero energy communities? Getting to net zero energy at the community level means maximizing the energy efficiency of each building in that community, including many existing buildings, and meeting the remaining energy demand with renewable energy.
Supplying the renewable energy component can be easier at the community level because sites are typically available to accommodate larger-scale, high-efficiency solar photovoltaic installations. Beyond that, net zero energy in communities can be managed over time rather than completed as a single, all-encompassing project. This tends to lower the cost and reduce disruption to building occupants.
By balancing the cost-effectiveness of energy efficiency with renewable energy options, communities can find a minimum-cost pathway to net zero energy. Various financial mechanisms exist to help pay for the incremental cost. Increased asset values, increased comfort, increased energy independence, lower maintenance and energy costs and the potential for lower life-cycle costs are among the reasons communities are considering net zero energy.