Much has been written about energy efficiency and sustainability in relation to new-construction projects. But what about existing facilities? Are there significant efficiency gains to be realized?

With the latest revision of the U.S. Green Building Council's Leadership in Energy and Environmental Design for Existing Buildings (LEED-EB) Green Building Rating System, we have an answer, and that answer is yes. LEED-EB focuses on the issues most important to building owners: reduced energy and water consumption and improved operational efficiency. Its scope includes performance-based design, retrofit, commissioning, operation, and maintenance over the life of a facility.

This article will discuss investment trends related to energy efficiency, review proven cost-effective energy-saving measures for existing facilities, and provide real-world examples of successful retrofits.

INVESTMENT TRENDS

An online survey of 1,249 North American executives and managers responsible for energy-management decisions commissioned by Johnson Controls and conducted in March 2007 revealed that:

• Seventy-nine percent believed energy prices would rise significantly over the next year, with an average increase of 13.3 percent expected.

• Fifty-seven percent expected to make energy-efficiency investments over the next year, with an average of 8 percent of their capital budget used.

• Eighty percent expected to fund energy-efficiency improvements through their operating budget, with an average of 6 percent of their budget used.

Forty-eight percent of the respondents said environmental responsibility motivated their investment decisions at least as much as cost reduction did. Nonetheless, their organizations largely had not relaxed their return-on-investment requirements for energy-efficiency measures.

The organizations of 64 percent of the respondents had a maximum payback period between two and five years. The organizations of only 16 percent of the respondents would tolerate a payback period of six years or more. Overall, only 18 percent of those surveyed said their organization allowed a longer payback period than it did five years ago; however, 26 percent of larger enterprises (those with 500,000 sq ft or more) were tolerating a longer payback period. For organizations of all sizes, the payback period of about 45 percent had not changed over the previous five years.

It appears that economics prevail in investment decisions, with environmental responsibility almost on par. So, how do we best work with this investment mindset and help owners and managers optimize energy efficiency in existing buildings? The answer is with a combination of proven energy-efficiency strategies and solutions enhanced and enabled by new and available technology.

PROVEN ENERGY-SAVING MEASURES

An energy audit is the starting point and most powerful tool we have in creating effective energy-efficiency solutions. Technology, however, has vastly improved the ability of energy engineers to collect and analyze data. Hand-held computers and compact digital cameras, for example, have improved the speed and accuracy of gathering, cataloguing, and interpreting building-system and energy-usage inputs. In multibuilding and multi-location audits, electronic files and photographs can be shared easily and quickly, resulting in shorter response times and more comprehensive energy-efficiency recommendations.

While specific recommendations vary based on building type, use, and location; local utility-rate structures; and the related objectives and budgets of the building owner and management staff, there are areas in which energy-efficiency improvements are likely to be found in existing buildings, including:

• Lighting

  Lighting typically accounts for 30 percent of energy use in non-residential buildings. A lighting retrofit, including the use of higher-efficiency ballasts and/or lamps, can directly reduce the energy used for lighting and indirectly reduce the demand for air-conditioning.

• Demand-response controls

  Especially in capacity-constrained areas, it is critical to evaluate utility-rate structures and have the ability to reduce building electrical demand by turning off equipment or systems for defined periods of time. For example, with Internet Protocol-addressable ballasts, lighting could be reduced by 50 percent in selected areas during bright daylight hours.

• Premium-efficiency motors

  Installing new high-efficiency motors on pumps, fans, and other components can yield substantial energy savings with a relatively short payback, as well as increase reliability and reduce maintenance.

• Chilled- and condenser-water temperature

  Chillers typically spend less than 1 percent of their operating hours at design conditions; the other 99-plus percent are spent at off-design conditions coinciding with milder outdoor temperatures and/or lower humidity levels. Taking full advantage of these conditions is one way to reduce energy consumption.

• Variable-speed drives (VSDs)

  VSDs continuously and precisely match motor speed to the demand on a motor. With a large-tonnage chiller system, a VSD retrofit can reduce annual energy consumption by 30 percent. (See “Chiller-Driveline Retrofits” sidebar.)

• Outdated-equipment replacement

  Dramatic efficiency gains have been made in all categories of HVAC equipment. In many cases, other energy-efficiency measures (e.g., new lighting systems) or changes in building-use patterns have reduced cooling or heating load, meaning new equipment can be smaller in capacity (or staged to meet demand more efficiently).

• Variable air volume (VAV)

  Constant-volume air distribution, especially at high static pressure, is a known energy waster. Converting to a VAV system, whether overhead or underfloor, can reduce energy consumption by more closely matching airflow to temperature set points at, in many cases, lower static pressure.

• Solar power

  A power-purchase agreement (PPA) is a long-term agreement to buy power from a company that produces electricity. With a solar PPA, a provider builds a solar-energy facility on a customer's site and operates and maintains it for a defined period of time (usually, 15 years or more). Generally, it ensures energy rates that are lower and less volatile than those of the local utility. What's more, operating and maintenance costs are covered, with the building owner paying for only the electricity that is consumed.