Defining zero net energy building and motivating owners to make it standard

“Going green” has become a household phrase. We ask ourselves, “What can we do to help the environment?” In the same fashion, building owners advocate reducing their carbon footprint and work to design energy efficient buildings. To them, zero net energy (ZNE) is not a foreign concept. Even though the familiarity of ZNE is present, we recently learned that ZNE buildings are not mainstream, and while efforts are progressing, the uptick in ZNE design is only marginal. Why is this the case? In a recent issue of the ASHRAE Journal, experts clear up misconceptions of ZNE by clarifying the approach, highlighting the benefits, and providing recommendations on how to motivate building owners to make ZNE building a standard.

Defining a Zero Net Energy Building

Experts define a zero net energy building as the following:

  • “One that contributes to the goal of reducing greenhouse gas (GHG) emissions from the energy use in the build environment, through offsetting the energy use with clean energy generation within the boundary drawn for the context.” – Smita Gupta
  • “The U.S. Department of Energy and ASHRAE members say it’s when the sum of all energy that is delivered to the property line is less than the energy that is exported from the property.” – Charles Eley

At its simplest form, a ZNE building is a self-sufficient, energy-efficient building. It can power its systems and operations from on-site renewable exported energy and requires little delivered energy.

California, for example, set goals to have all new residential building construction to be ZNE by 2020 and all commercial construction by 2030. California Green Building Standards include define zero energy in a  low-rise residential building as one whose energy consumption of water heating loads and HVAC must be at least 15%-30% less than energy code compliance. This depends of course on the climate and whole building energy consumption, and must have an energy design rating (EDR) less than or equal to zero.

Zero Net Energy Building Benefits

Designing a zero net energy building clearly contributes to reducing a carbon footprint. Here are other benefits that experts highlight:

  • Zero net energy buildings provide a healthy and comfortable environment for their occupants
  • They are by and large a good investment (a financial cost up front, a utility savings over time)
  • They encourage occupant conservation at work and home
  • They reduce the environmental costs of energy production, including toxic waste, gas emissions, air and thermal pollution
  • They are resilient against grid outages

Motivating Owners to Build ZNE Buildings

Designing energy efficient buildings is a conversation on the table for many building owners. While tweaking systems and processes to become more efficient is widespread, the movement for designing new ZNE buildings has a slow uptick. Many owners know it’s a good investment, but are hesitant on implementing plans. What motivates owners to say “yes” in the end?

First, ZNE has to be a part of the initial conversation. Building owners need it to be a goal and not just an add-on. This way, stakeholders can explore different strategies and settle on one that captures the needs of the owner and lays out the best energy efficient design. Secondly, the conversation needs to include numbers (e.g. operating costs and savings over time) to prevent any anticipated sticker shock. Finally, to motivate building owners, one must talk up rewards and recognition. Owners enjoy receiving recognition for having an energy efficient building. As expert Paul Torcellini writes, a ZNE building automatically gives building owners “bragging rights”. If the return on investment isn’t enough to sway building owners, their name in lights is an excellent selling point.

Source: ASHRAE’s A Conversation on Zero Net Energy Buildings with roundtable experts Bing Liu, Charles Eley, Smita Gupta, Cathy Higgins, Jessica Iplikci, Jon McHugh, Michael Rosenberg, and Paul Torcellini