Net-Zero Snapshop of Energy Future

Posted on April 27, 2011


As sustainable design becomes truly mainstream, which I define as adopted into required building code, initiatives for those who want to lead will become more aggressive. Sustainable design leaders asked what the ultimate goal is for their buildings may answer:  net-zero, or buildings having a neutral energy impact on their environment. More specifically, a net-zero building creates enough energy on site to balance its yearly demand. A recent article in Architectural Record and “Targeting Net-Zero” in Building Green profiles one of these net-zero projects.

Interesting, there were some unusual risks and rewards for participants on this project for the National Renewable Energy Laboratory (NREL).  The winning team, RNL (designer) and Haselden (builder), spent $1.2 million on their competition proposal to win the project, with the opportunity to earn $2 million if the project met budget, schedule and energy performance goals. The client was sophisticated to use design-build, and be sure to note “the goal was not to build the least expensive building…we wanted to achieve the best value with the money we had available.”

The project did achieve its goal.  Perhaps the most obvious yet important realization with such a daunting challenge is that “no one move would make reaching net-zero possible.  The building would need to rely on a host of tightly coordinated strategies, each offering an incremental benefit.” Several innovations allowed this to occur, including a “transpired solar collector”, a labyrinth of cavities that transported heat throughout the building floor cavities without forced mechanical ventilation, and photochromic glass that dims in response to the sun. The building’s width, 60 feet, was a depth the team derived which facilitates penetration of daylight and ventilation when used with other daylight system components like light shelves and louvers. Daylighting provided a huge reduction in electric use and its attendant heat load created by lights.

A final important lesson that can be used on any project is that all the design and engineering in the world cannot control building users, and occupants have a large impact on the targeted energy conservation goals and net-zero threshold. Without tenant energy conservation measures, the building would achieve 63% savings; with tenant efforts, plug loads drop eight percent and lighting, heating, pump and domestic hot water all drop another percent for a 75% savings against a comparable benchmark.

For a design team to produce a net-zero building, here are some general net-zero strategies from the articles to remember:

  • Modeling tools are essential.  DOE’s eQuest helped model window, daylight and heat transfer.
  • Climate and building type are important for design viability because this affects daylighting, ventilation, and opportunities for photovoltaics.  “Most net-zero projects use photovoltaics as the primary renewable source for electricity.”
  • Net-zero rigor can be assisted by keeping the building off the electrical grid and self-reliant on independent energy generation.  In the case of this project, the electrical connection to the grid saved $125,000, which subsidized a large portion of the photovoltaic system.
  • Every opportunity for energy reduction must be utilized.  Monitoring and smart building technology helps reduce non-peak usage energy loads
  • “Approaches to achieving net-zero can be designed into the building without substantial costs.”
  • Net-zero is about “shifting costs.  You end up spending more money on design but less on construction.”
  • “What’s important about net-zero is to drive the intrinsic energy use as low as possible—50 to 80 percent range.”
  • Increased building efficiency will always be cheaper than paying for additional energy via a more robust photovoltaic array.

The Building Green article points out two take-aways that, although used to describe net-zero, can be used on any project:

“Basically, to reach net-zero affordably, designers must aggressively reduce energy demands and loads, optimize passive strategies, and, if needed, incorporate efficient active mechanical strategies.”

“With net-zero, it becomes important to incorporate a true integrated design approach, in which the architect and engineers are at the table developing performance efficiency at the earliest stages of the project.”

Net-zero or not, buildings are trending toward energy reduction through various strategies—system design, initial (passive) design, mechanical (active) strategies, and user behavior change. More importantly, to achieve design innovation and industry-leading performance, it takes ‘a true integrated design approach’ involving the whole team. The earlier this occurs, the better the results.