Even to get to the point where it makes sense to fill the gap with renewable energy purchase, facility managers with net-zero energy goals must place highest priority on efficiency. Of the three-legged stool of efficiency, on-site renewables and renewable procurement, energy efficiency has by far the most impact. What's more, it's a step that can be taken now and delivers immediate benefits.
"Energy efficiency is absolutely the most important," says Brenna Walraven, managing director, national property management for USAA Real Estate Company. "A building must be super energy efficient because that way you need to produce and buy less energy, ergo less cost to get to net-zero."
Energy efficiency is a familiar concept to facility managers. But when the goal is net-zero energy use, the term takes on a whole new meaning.
The math of energy efficiency seems pretty simple — if a standard code building uses about 70 kBtu per square foot, designing a building to use 35 kBtu per square foot means only half as much energy needs to be produced with on-site renewables or purchased from the utility or in renewable energy certificate (REC) form.
But doing that math in the first place is no easy feat. "You really need an energy consultant who is very good at running building models that are actually predictive of results," says Brad Jacobson, project manager and associate for EHDD Architecture. "And you need to continually optimize the design throughout the design process, not just run the model at the end to see if you hit a target."
Designing a building to use 50 percent less energy than traditional buildings means paying close attention to how building systems work together, both at initial design and when the building is operating.
For this reason, net-zero energy buildings require a very sophisticated whole-building integrated design process with clear net-zero energy goals from the beginning. And facility managers are ground zero for such net-zero goals.
"Facility managers are a great audience for net-zero energy because the idea empowers facility people," says Jacobson, whose firm has successfully completed several net-zero energy buildings. "Net-zero energy is something facility people can really sink their teeth into. My experience with facility people is that they are very good at hitting their goals."
Facility managers understand best how building systems work — and work together — during operation. For instance, lighting and the building exterior have profound effects on HVAC energy use, a fact sometimes overlooked during design. And these three main building systems are the keys to reducing energy use enough to make net-zero energy possible, say experts.
Daylighting plays a huge role because it greatly reduces electricity required for lighting. NREL's facility, for example, uses a "lazy H" configuration with two narrow 60-foot wings connected by a covered bridge. The relatively shallow floor plate and expanses of exposed exterior, along with light-reflecting devices, optimize the amount of natural light that can penetrate to the interior of the building.
One of the more overlooked components of a net-zero energy building is how plug loads will affect the energy accounting, says Jacobson. A general rule of thumb says that a building's energy load when in operation is about a third HVAC, a third lighting and a third plug loads. If that's the case, reducing lighting and HVAC by a significant amount but ignoring plug load efficiency means that plug loads represent a disproportionate percent of the building's energy use.
"Using photovoltaics to cover plug loads is absurd," says Jacobson. So the efficiency of everything from computers to printers to coffee makers should be considered, which is another reason the facility manager is critical to the planning process. Thinking about plug loads generally doesn't rate very high on a list of architects' priorities.
However, on a net-zero energy project Jacobson worked on, he says his team made recommendations about the most efficient products that still met the specifications the owner required for different devices. By taking the recommendations, the owner was able to reduce plug-load energy by 50 percent, save $750,000 on photovoltaic costs, and still achieve net-zero energy.
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