detail to defi ne a variety of potential energy- effi ciency improvements. These systems should include the building envelope; light- ing; heating, ventilation, air conditioning (HVAC); domestic hot water; plug loads; and compressed air and process uses (for manu- facturing, service or processing facilities). The audit begins with a detailed analysis
of energy consumption to quantify base loads, seasonal variation and effective energy costs. From there, the study should include an evaluation of lighting, air quality, temper- ature, ventilation, humidity, and other condi- tions that may affect energy performance and occupant comfort. A performance simulation is usually part of the process, so the team can estimate changes in energy usage resulting from potential optimization projects and compare those data to cost esti- mates to implement the projects. This can be a computer-simulation model, spreadsheet models or a variety of other engineering tools. The process also includes detailed discussions with the building ownership, management, and occupants to explore potential problem areas and clarify fi nancial and non-fi nancial goals of the program. The Level 2 audit should result in a clear
and concise report and briefi ng with the owner and management team describing a variety of energy-effi ciency measures (EEMs), including no- and low-cost mea- sures, modifi cations to system controls and building automation, operational changes and potential capital upgrades. The fi ndings should include general costs and perfor- mance metrics, as well as a means for the owner to evaluate the EEMs and decide how to proceed with implementation. Many of the EEMs revealed during the
ASHRAE Level 2 audit can be implemented quickly with rapid or immediate fi nancial payback for the owner. Other EEMs will require more detailed analysis of ben- efi t and cost and the other goals that are important to the owner. The audit should defi ne next steps to accomplish this analysis and decision-making, sometimes through discussion with manufacturers or suppliers or other relatively simple means. For other EEMs involving complex interaction among building systems and potentially large fi nancial investments, it may be necessary to dig deeper into the building operation and the human factors infl uencing perfor-
18 RETROFIT // March-April 2013
ASHRAE ENERGY AUDITS The following highlights what is involved in each level of an ASHRAE energy audit.
Type of Audit Highlights LEVEL 1
Rapid assessment of building energy systems Building energy benchmark
High-level definition of energy-system optimization opportunities Outline applicable incentive programs
LEVEL 2
Detailed building survey of systems and operations Breakdown of energy source and end use Identification of energy-efficiency measures (EEMs) for each energy system Range of savings and costs for the EEMs Spotlight on operational discrepancies
Outline priorities for limited resources, next steps, and identification of EEMs requiring more thorough data collection and analysis (Level 3)
LEVEL 3
Longer-term data collection and analysis Whole-building computer simulation calibrated with field data
Accurate modeling of EEMs and power/energy response Bid-level construction cost estimating Investment-grade, decision-making support
mance. This is where the ASHRAE Level 3 audit becomes essential.
ASHRAE LEVEL 3: DETAILED ANALYSIS OF CAPITAL- INTENSIVE MODIFICATIONS Some of the system upgrades or retrofi ts revealed by the Level 2 audit may require signifi cant investments of capital, personnel and other limited resources. Before making this level of investment, the owner will want to have a much more thorough and detailed understanding of the benefi ts, costs and per- formance expectations. This is the purpose of the “investment-grade” Level 3 ASHRAE audit. There may be only a few capital-inten-
sive EEMs exposed by the Level 2 audit or there may be dozens for larger facilities. Investment levels can range from tens of thousands to tens of millions of dollars. In most cases, because this cannot be clearly determined or accurately estimated in advance, the recommendation and scope defi nition for a Level 3 audit usually is an outcome of the Level 2 process. The ASHRAE Level 3 audit usually focuses
on a “whole-building computer simulation,” where a computer program is used to very accurately model the way the brick-and-mor- tar building would respond to changes in the energy systems—whether those are major HVAC retrofi ts or architectural modifi cations to walls, windows and roof. The ASHRAE Level
3 audit involves much more detailed data collection during the course of weeks or months. Data loggers typically will be placed temporarily to monitor the operation of pumps and motors, temperatures of affected spaces, lighting levels, switching behavior and other factors. These data are used to calibrate the computer model, so it responds to inputs and changes the same way the building could be expected to respond. This calibration is checked and validated by simu- lating a year or more of historical climate conditions to determine whether power and energy usage in the model mirrors actual energy power and energy usage. Once the computer model is respond-
ing like the real building, changes to energy systems can be simulated with very ac- curate results. Combining that process with construction-grade cost estimating sup- ports informed investment decisions.
BEFORE THE AUDIT Before beginning an energy audit for a building or portfolio of build- ings, St. Louis-based Microgrid Solar recommends a preliminary energy-use analysis to compare the Energy Usage Index of each building with the national average and to identify high- and low- energy performers. This typically is done using the Energy Star Portfolio Manager benchmark- ing tool. The analysis requires access to energy consumption and cost data for the last 12 to 36 months. Once this “benchmarking” analysis is complete, a recommendation is made as to which buildings should be audited first and the type of audits to be carried out.
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