To enter Midtown Manhattan at night via the Queensboro Bridge is as if arriving by spacecraft into the belly of a shimmering, glass encrusted starship. Iconic against the skyline is the Empire State Building, the spire glowing in the colors of the season. On a May night in 2012, the Empire State Building glowed green in honor of the Rocky Mountain Institute (RMI) which championed deep energy retrofits to the building, saving 38% of building energy at an annual cost savings of $4.4 million. The child in me wondered, “Who is the poor guy responsible for changing all of those light bulbs?”
The US Department of Energy (DOE) defines a Zero Energy Building (ZEB) as one that produces enough renewable energy (electricity, fuel combustion) to meet its own annual energy consumption requirements. The building terms, “Net Zero Energy” (“NZE” or “net-zero”) and “Zero Net Energy” (ZNE) are synonymous and are broadly used in the industry.
Leadership in the ZEB world is emerging at the municipal level where cities are actively pursuing incremental improvements in the energy performance of commercial buildings rather than jumping directly into ZEB requirements. Municipal leadership is exemplified by the Global Covenant of Mayors, a compact between thousands of cities globally, to set mitigation commitments, report activities, and share best practices on a common platform, addressing building energy use, improving building codes, establishing developer incentives and property assessed clean energy (PACE) programs, and promoting sub-metering.¹
Practically, for an existing building to achieve ZEB status, the critical step is conducting a deep energy retrofit, which provides significant standalone cost savings benefit regardless of whether the building attains net-zero status. Once deep energy retrofits are instituted, the building or building campus can undergo an energy assessment to match an appropriately sized energy system. Deep energy retrofits result from a whole-building analysis and construction process which fundamentally enhances the building value and achieve much larger energy cost savings than those of conventional, simple retrofits. Deep energy retrofit planning first evaluates all major capital improvements necessary over the next several years to serve as the baseline cost and then strategically evaluates opportunities for capturing other benefits such as managing utility costs, attracting and retaining desired employees and tenants, improved reputation and leadership, and complying with present and future sustainability reporting requirements.
While capital improvement analysis utilizes simple payback analyses based on energy cost savings alone, using traditional discounted cash flow analysis over the building ownership time period, deep energy retrofit financial analysis should consider other non-energy-cost values that benefit building owners and occupants including the following variables.²
The Empire State Building retrofit included the remanufacturing of its 6,514 windows onsite into superwindows, cutting winter heat loss by at least two-thirds and summer heat gain by half, the advanced glazing along with improved lighting and office equipment will cut the building’s peak cooling load by one-third. The original budget for energy related projects (projects that may somehow affect energy use) was approximately $93 million. This energy budget included a project to replace the chiller plant to increase cooling capacity, which would have required tearing up Fifth Avenue to bring the new chillers into the building. However, by first implementing strategies that reduced the buildings cooling demand, it was possible to reduce the cooling capacity by 1,600 tons allowing the chillers to be retrofit rather than replaced for a capital savings of $17.3 million.³
In Los Angeles, commercial buildings account for nearly 65 percent of energy use in the city, as well as, greenhouse gas emissions. As mentioned earlier, California standards have been set for all new residential construction to be built at ZNE by 2020, all new commercial buildings be built to ZNE by 2030, and 50% of existing commercial buildings be retrofit to ZNE by 2030.