Energy modeling, according to the American Institute of Architects (AIA), is the practice of simulating the energy performance of an entire building or the systems within a building. According to Dennis Knight, P.E., principal of Whole Building Systems LLC, Charleston, S.C., energy modeling is “the practice of using math, science, engineering, analytic tools, skills and judgment to simulate the functional characteristics of energy use of systems, their components, and processes within a building or industry to estimate the demand for, and consumption of, energy resources and, often, the associated cost.”
Although such a model can be built using hand calculations, computer modeling software is normally used to provide a more whole-building simulation. According to Erik Kolderup, P.E., BEMP, LEED AP, principal of Kolderup Consulting, San Francisco, the modeler first enters a great number of data points about the building’s physical characteristics and chooses typical yearly meteorological weather data, and then the energy modeling tool provides a series of reports of predicted energy use for the heating, ventilating and air conditioning (HVAC); water; and electrical systems.
The tool, added John Kennedy, senior manager of building performance analysis products for Autodesk Inc. San Rafael, Calif., “takes all this input and generates a model of what will occur throughout the building, calculates the corresponding heat loss or gain, and then calculates the energy required to operate systems.”
The power of the model is how it enables designers to make changes to surfaces, equipment, building orientation and the like, and see what the effect will be, long before construction begins.
“A computer model simulation, however, typically takes time, can be a more expensive analysis and requires someone with experience using modeling software,” Kolderup said.
However, while simulations can be powerful, there still is a role for hand calculations in energy modeling, even though the approach requires a lot of assumptions.
“It’s good to use the manual approach to check computer calculations from time to time,” Kennedy said.
Hand calculations, however, actually are preferred when the energy-conservation methods being considered are for a stand-alone system or if the contractor, designer or building owner desires a simple analysis of discrete systems or components.
“For example, hand calculations are ideal for a lighting upgrade project where the goal of the modeling exercise is just to determine the difference in the cost of operating one lighting system for a specific period of time as compared to another or to determine whether changing the motors in a water treatment facility from standard to premium efficiency is desired,” Knight said.
Hand calculations may be quicker and more accurate for specific tasks, but the manual method doesn’t capture whole-building performance and the interactive effects of different systems, such as how changes to a lighting system may affect HVAC usage.
Depth seems to be energy modeling’s distinguishing characteristic. Even though they may look the same on paper or on the screen, as the case may be, energy modeling shouldn’t be confused with energy audits.
“An energy audit is a quick review of usage, which includes examining utility bills and the building’s technology, to calculate upgrade recommendations and estimate energy and cost savings,” Kennedy said.
Audits, therefore, do not account for building system interrelationships and the effect that a change in one system might have in the performance of another.
However, energy modeling is a tool that can be used as part of an energy audit process that estimates potential savings for retrofit projects, Kolderup said.
“It’s not always necessary or appropriate to perform energy modeling as part of an audit. The need for that level of sophistication depends on the energy-conservation opportunities that are available and the goals of the owner,” he said.
For example, if the building owner wants to know the effect on consumption of changing the lighting system, then a regular audit with manual calculations would be sufficient. However, dealing with more structural issues, such as window replacement, probably calls for using an energy model. For instance, one of the most appropriate uses is in the relative study of predicted building energy performance in commercial and even residential applications and comparing design options.
“For example,” Kolderup said, “an energy model can compare the impacts of choosing among different options for equipment, glass and lighting systems.”
Energy modeling is used least in industrial applications, however, because those facilities are typically designed for more unique processes that would require an extremely customized approach.
“The use of energy modeling is ideal when there is a need to either build or renovate a facility, upgrade a system or components, or create or improve a process,” Knight said.
Once the need for some type of improvement is identified— because existing facilities or equipment have expended their usefulness based on their age, the systems become obsolete and can no longer be maintained or serviced, or regulatory mandates or incentives become available—energy modeling can identify the best solution.
There is a cost, of course, associated with energy modeling, and it varies with the complexity of the building. According to the AIA, energy modeling should be presented as worth the price premiums, as the building will be more comfortable and perform more reliably. In many instances, the cost can be recovered through credits for specification tradeoffs and/or by qualifying for available incentives and rebates.
And with the increased pressure to build new or retrofit old buildings to qualify for green building certification, energy modeling can help determine determining the potential certification score of any proposed energy conservation method.
“In addition, energy modeling enables the owner to understand the building’s energy use and determine both present and future performance,” Kennedy said.
Offering energy modeling
According to Knight, if electrical contractors can gain the requisite knowledge through education and experience to provide energy modeling or are willing to subcontract that part of the project out to competent third parties, they could expand their service offerings to include energy-efficiency upgrades, lighting retrofits, retrocommissioning of electrical systems, and building automation system (BAS) services.
“However, to do so, contractors need to know the market they intend to pursue and how energy modeling enables them to provide a better, more comprehensive service to their clients,” Knight said.
They also need to know their current competence levels to use or apply energy modeling techniques, and they need to research any additional licensing or registration requirements, which vary on a jurisdiction-by-jurisdiction basis.
Kolderup, however, pointed out that modeling is typically performed in today’s market by mechanical contractors and engineers and that lighting systems don’t often warrant the use of modeling, although contractors can certainly influence lighting system decisions during the design phase.
“In a growing energy retrofit market, contractors can certainly provide energy savings estimation services for lighting systems, and, eventually, for HVAC and building envelope retrofits as they gain expertise,” Kennedy said. “Electrical contractors can work closely with the energy modeler to better determine the design of the building’s electrical and mechanical systems and to ensure easy adaptation to upcoming energy codes.”
New tools and applications for energy modeling are coming to market frequently, according to the AIA. With the widespread use of computers, the use of energy modeling is becoming more common and expected. One barrier to wider use, however, is the time that energy modeling takes.
“Software tools are certainly improving, and the industry is seeking to integrate building information modeling programs and energy modeling software,” Kolderup said.
Energy modeling software providers also are working to develop more user-friendly graphical interfaces and more cost-effective tools that will expose comprehensive energy modeling capabilities to a wider group of design and construction professionals, Knight said.
“Energy modeling will increasingly be used to target building energy use and performance to establish baseline metrics and to demonstrate compliance with high performance building guidelines,” he said.
One such tool for electrical contractors is NECA WORKS software, for members of the National Electrical Contractors Association (NECA). According to Stan Lazarian, who chairs NECA’s Energy Solutions Task Force, “The new NECA WORKS software, available to all NECA members, is an excellent economic modeling tool which layers multiple energy-efficiency projects and incentives on top of each other into a single project to arrive at a combined benefit.” Find out more at www.necanet.org/works.
Although not yet required, certification programs—such as American Society of Heating, Refrigerating and Air-Conditioning Engineers’s Building Energy Modeling Program, which certifies individuals’ ability to evaluate, choose, use, calibrate and interpret the results of energy modeling software—already exist, and Kennedy expects requirements for certification to broaden as market demands for energy modeling services increase. In addition, contractors can partner with energy modeling consultants, consulting engineers, energy managers, mechanical designers and building performance analysts to learn about modeling and to potentially become a complete source of energy solutions.
BREMER, a freelance writer based in Solomons, Md., contributes frequently to ELECTRICAL CONTRACTOR. She can be reached at 410.394.6966 and firstname.lastname@example.org.