Building Operations

Written by R. Kirk Johnson, AIA, LEED AP

One of the key elements contained within the LEED 2009 for Existing Buildings Rating System, is the relationship between the energy optimization requirements of the standard with the industry leading Energy Star rating measurement program.  LEED 2009 for Existing Buildings uses the Energy Star measurement standard as the entry point into minimum building energy and atmosphere compliance. Energy Star is a program administered by the United States Environmental Protection Agency (EPA) and Department of Energy (DOE) pertaining to building energy consumption.  Many of us are familiar with the brand recognized Energy Star label when purchasing appliances such as dishwashers, refrigerators, air conditioners, and other similar consumer products.  The same brand is also used to rate building performance through the Energy Star Label program.  LEED requires a minimum score of 69 as an energy and atmosphere pre-requisite.

 

According to the United States EPA buildings consume approximately $200 billion dollars of electricity and natural gas per year in facility operations.  Commercial and industrial buildings are also responsible for nearly 50 percent of national greenhouse gas emissions.  The department estimates that every 10 percent of building energy savings would reduce the greenhouse emissions equivalent to 30 million vehicles.  The math is straightforward. The solution is complex.  A common starting point is the partnership between the LEED EB Rating system and the Energy Star program.

PERFORMANCE MANAGEMENT

The two systems, although variant, at the energy consumption level complement each other.  As such, buildings may obtain both LEED and Energy Star ratings.  LEED 2009 for Existing Buildings uses the same online Portfolio Manager Web based tools in determining building energy use to benchmark energy performance of similar facilities.  Energy Star performance ratings help stakeholders determine general energy compliance relative to a normalized national inventory of similar buildings rather than a specific individual approach mandated by energy code regulations.  Commercial Buildings such as Bank branches, Courthouses, Dormitories, Financial centers, Hospitals, Hotels, K-12 schools, Medical Offices, Offices, Retailers, Supermarkets, Warehouses, and various types of manufacturing plants are basic building types available in the Portfolio Manager toolset.

LEED EB MINIMUM REQUIREMENTS

LEED 2009 for Existing Buildings requires a minimum Energy Star Rating threshold as a prerequisite for certification and allows additional energy optimization credits for facilities that exceed the minimum point energy star threshold.  LEED EB Energy and Atmosphere credit 1 allows up to 18 additional credits for increased levels of operating energy performance relative to the Energy Star rating.  LEED requires actual metered energy consumption data for a continuous twelve month period to be utilized in calculations of building energy performance.

LEED 2009 for Existing Buildings provides two avenues of compliance depending on the facility typology and EPA Energy Star Portfolio Manager building database.  Projects containing building types that are measured by Portfolio Manager may use Option 1 comparison metrics.  Projects of building types that are not measured by Portfolio Manager may use an alternate method demonstrating energy efficiencies over building peers as identified in the Commercial Building Energy Consumption Survey.  All documentation must provide a full twelve months of continuous actual measured energy consumption data during the performance period.

ENERGY ASSESSMENT

Energy Star uses a comprehensive approach to energy assessment using source energy, identified as the total amount of raw fuel that is required to operate the building.  In addition to localized building site energy reflected in utility bills, source energy factors additional energy elements such as transmission, storage, delivery, and production losses associated with consumption.  These factors are calculated by nationally applied EPA source-site ratios to determine the equivalent source units for the project.  Detailed information regarding source energy can be downloaded from the Energy Star website.

In order to meet the prerequisite requirements under LEED EB 2009, a minimum Energy Star performance measurement must be achieved.  Under the assessment, Energy Star ranks building energy performance similarly to ratings used with appliances or systems used to indicate estimated mileage with automobiles.  Utilizing a traditional 100 point building evaluation scale, each facility is ranked as per improvement percentage over buildings with similar attributes. In this scenario, a score of 25 indicates that a building performs better than 25 percent of similar buildings, a score of 50 indicates average performance, and a score of 75 indicates the building energy usage performs better than 75 percent of nationwide buildings.  The score is determined by sophisticated statistical normalization algorithms and representational sampling that take into account building variables such as climate conditions, location, size, occupancy, operating patterns, number of computers, and other similar activities affecting energy consumption.  The overall indication indicates an Energy Use Index (EUI) for the facility.

These statistical representative models, based on collective energy use information obtained from the Commercial Building Energy Consumption Survey (CBECS) conducted by the Department of Energy’s Energy Information Administration are used to compare a building against other similar buildings within the peer group.  The national survey is conducted periodically by gathering building typology and energy use from multiple buildings located across the United States.  The most recent study, 2003 CBECS National Average Source Energy Use and Performance Comparisons, can be downloaded from the EPA website and another version is scheduled for another release later this year.

ENERGY STAR AND ENERGY CODES

LEED 2009 for Existing Buildings uses Energy Star for general compliance rather than an energy model compliant to energy codes and ASHRAE standards.  Although an energy model based upon ASHRAE 90.1 can be used in other LEED Rating Systems, Energy Star ratings are used in LEED 2009 for Existing Buildings.  However, it is important to note that Energy Star measurement is tied to an aggregate performance metric whereas energy code compliance is regulated at an individual site specific building level.  As a result, there is not a direct correlation between the EPA rating and other energy code regulations such as ASHRAE 90.1 or International Energy Code.  In essence they are comparing different items in similar manners as apples and oranges, which both may be fruit but are totally different.  These specific energy regulations evaluate singular building performance relative to a hypothetical baseline model meeting the prescriptive requirements of the standards.  The percentage improvements are determined by the difference between the proposed and baseline individual building conditions.  Energy Star, however, uses a normalized collective model to determine where the building ranks in relation to its peers.  

PORTFOLIO MANAGER

According to the EPA, Portfolio Manager is “an interactive energy management tool that allows you to track and assess energy and water consumption across your entire portfolio of buildings in a secure online environment.”  The input information is required for LEED EB certification.

TARGET FINDER

Target Finder is similar to the Portfolio Manager except that it is used to determine energy usage index targets and rate the building design estimated energy usage.  They both are interactive tools that use the same metric information derived from the CBECS and evaluation criteria such as localized climate conditions and energy mix rates.  However, the required data inputs used in Target Finder are a subset of those used in Portfolio Manager.  The required data inputs consist of the primary drivers of energy usage and the estimated energy use intensity (EUI) is generated in the outputs.

ENERGY MANAGEMENT GUIDELINES

Many times applicants of LEED EB projects need to determine proven methodologies that may be considered in order to reach particular Energy Star ratings.  The EPA website provides many helpful resources to assist with these energy management and optimization endeavors.

As you can see, the threaded integration of the LEED for Existing Buildings Rating system and the EPA Energy Star rating classification are essential in achieving LEED certification.

• Resources
• Portfolio Manager
• Guidelines for Energy Management
• Energy Performance Targets
• 2003 CBECS National Average Source Energy Use and Performance Comparisons
• Architecture 2030