ASHRAE Journal - December 2009 - 20

How Building EQ Works By Dan Nall P Member ASHRAE .E., Two Rating Systems Share Similar Scale The Asset Rating achieves this normalization through energy modeling of the he ASHRAE Building Energy Quotient (Building EQ) incorporates two physical building as it currently exists, distinct ratings. Each has a specific purpose and calculation meth- using standard occupancy and operational schedules, and standard equipment odology. The two ratings share a similar scale, with zero being best, 100 and occupant densities that have been being the median and values above 100 being worse than average. developed for each occupancy type. The median source EUI would be the same as The scale is a ratio of the source Energy Use Index (EUI) for the subject build- used for the Operational Rating. Following are some features of an Asing, divided by the median source EUI for that type of building in that climate zone. set Rating: • Rates the building, not the occupancy The Operational Rating (In Operation) • Good for use in existing building enprovides information on the actual energy ergy efficiency incentive programs; and and operation; • Focus is on the physical building use of a building and is based on a com• Good for managing building portfocharacteristics—the “bricks and morbination of the structure of the building lios over time. and how it is operated. Example: U.S. EPA’s ENERGY STAR tar”—plus permanent energy systems; • Differences in operational behavior Information learned through subse- Portfolio Manager. quent years of operational labels can The Building EQ Asset Rating (As De- are ignored; • Rating is derived from a model-based provide building owners and operations signed) is intended to be a measure of the and maintenance staff with valuable in- energy efficiency quality of the as-built estimate of energy use, compared to a sight into how the building performs, op- fixed physical components of a building. It stock median or building code baseline portunities for improvement, and where differs from the current LEED Energy and for the building type; • No inherent requirement for field similar buildings fall in comparison. Atmosphere Credit 1 in that it is intended It also provides a means for owners to allow comparison among similar build- verification; and • It is a basis for energy efficiency of portfolios of several buildings to ings within a size range and of the same code compliance and beyond-code new identify priorities for energy savings occupancy type within a climate zone. investment. The Asset Rating is designed to be construction incentive programs. Examples: RESNET and CEC Home Following are key features of an op- relevant for real estate transactions. It erational rating: expresses an integral measure of the Energy Rating Systems. • Objective is to improve operations; building’s inherent energy efficiency. • Rating is based on measured energy Essentially, the Asset Rating evaluates About the Author use, adjusted for weather; the building “hardware” by calculating a Dan Nall, P is a senior vice president at Flack .E., • Field verification is a requirement; source EUI based on normalized “soft- & Kurtz in New York. Nall was a member of the • Ratings are sometimes adjusted ware” (the operations, occupancy and ASHRAE Building Energy Labeling Implementation based on levels of service; usage patterns of the building). Committee. T It’s the Law Energy Labeling in the UK By Hywel Davies, Ph.D., Member ASHRAE The ASHRAE Building EQ program would be appropriate should a rating program be required by a local, state or national government. This was the case in the United Kingdom, which enacted a labeling program in 2008 that uses energy labels, known as Energy Performance Certificates (EPCs). This assesses the potential energy efficiency of the building, independently of how it’s used. These labels are a requirement of the Energy Performance of Buildings Directive, introduced by 20 ASHRAE Journal the European Union (EU) to improve the energy efficiency of buildings, cut carbon emissions, reduce energy demands and improve European energy security by reducing dependence on oil and gas from the Middle East and Russia. EPCs are produced using an approved software package, which generates a numerical Asset Rating, where zero is zero See UK, Page 21 About the Author Hywel Davies, Ph.D., is the technical director at the Chartered Institution of Building Services Engineers (CIBSE) in London. He was a member of the ASHRAE Building Energy Labeling Implementation Committee. ashrae.org December 2009

ASHRAE Journal - December 2009

Table of Contents for the Digital Edition of ASHRAE Journal - December 2009