Renewable Energy: How Low Can You Go?

By Anne Cosgrove
Published in the July 2012 issue of
Today’s Facility Manager

Finding ways to increase energy efficiency is a major focus for many facility managers (fms). Operating a facility that consumes no energy at all may be unrealistic, but zero energy buildings (ZEBs) can be the next best thing. Also known as net zero energy buildings, ZEBs use no more energy annually than their on-site renewable sources produce. As a result, the amount of energy consumed from outside sources (e.g., “the grid”) is net zero.

Earlier this year, the New Buildings Institute (NBI) released a report on the state of ZEBs in the commercial sector. Produced with support from the National Association of State Energy Officials (NASEO) and the Commercial Buildings Consortium (CBC), “Getting To Zero 2012 Status Update” studied facilities functioning as ZEBs. The report aimed at identifying design and operations factors and incremental (increased) construction costs.

The report identified 21 ZEBs in the U.S., and to supplement this data, NBI expanded the scope to include 29 Zero Energy-Capable (ZEC) buildings. A ZEC building is one so energy efficient that it could be expected to be a ZEB if renewable energy was added to its operations.

The majority of ZEB buildings are located in mild or moderate climates. However, several operate in the more extreme climates of Minnesota, Wisconsin, and New York. Meanwhile, the majority of ZEBs are relatively small facilities—less than 15,000 square feet—and they are “demonstration buildings” such as environmental centers or education facilities. Commenting on this, Stacey Hobart, communications director for NBI, says, “This trend is similar to the beginning of the green building movement. Small project examples allow design teams to test strategies and technology applications with relatively low risk.”

And there are recent projects that are larger and host traditional occupancies. One example of a larger ZEB is Richardsville Elementary School in Bowling Green, KY. Completed in 2010, the 72,000 square foot facility was the third project the school district executed with ZEB in its sights. Daylighting and HVAC strategies were carried forward from previous projects. Meanwhile, energy monitoring in the other schools revealed kitchens and computer labs as significant energy consumers, so designers tackled those items for the Richardsville school.

Worth noting is that nearly all the technology used in ZEB buildings are commercially available (see chart below). In addition, integrated design with attention to building siting/layout/envelope and mechanical and electrical systems is critical. According to NBI, the most cost-effective path to zero energy is to focus first on those items. This, in turn, reduces the amount of energy required from renewable sources.

Source: New Buildings Institute

All ZEB buildings in the report employ solar photovoltaics (PVs) to produce their energy on-site. Hobart says this is “because it is the most broadly applicable technology. Wind power is an option, but it is limited by the feasibility of wind production at a site. PVs are generally a more predictable generator of electricity.”

Incremental construction costs were available from only a few projects. However, those reported show lower overall incremental costs (0% to 10%) than modeled estimates (3% to 18%).

Commenting on potential for increased ZEBs, Hobart observes, “Obstacles include lack of broad capability in the design community, cost, in some cases, and perception that it is not feasible. In some cases, these may be valid barriers. More complicated buildings, like hospitals, will likely not be able to achieve zero energy in the near term. However, one of the major obstacles we found relates to lack of willingness by an owner to set out a zero energy goal. We have evidence that zero energy is within reach for a number of building types, and most of our examples include a willing owner that directed the design team to this goal.”

Download a copy of “Getting To Zero 2012 Status Update” at the NBI website.