What is an Energy Model?

An energy model is a simulation created with computer software to determine a building’s energy use given specific variables. There are many energy modeling programs (the Department of Energy has indexed nearly 50) that range from free software to highly proprietary software designed for specific types of buildings and thermodynamic conditions. Most models utilize information on building design, envelope, orientation, weather, schedules, controls, and energy-using systems to project comparative energy consumption and costs. While the energy model is not used to predict energy bills, it is used to compare the overall performance of building design versus a baseline approach which meets a common building standard, like the ASHRAE 90.1-2004 Energy Standard. What is even more useful is to compare specific or combined energy conservation measures versus a baseline design. These measures could include changing the building orientation, adding better glazing, improving chiller efficiency, or implementing daylighting strategies. The accuracy of the energy model largely depends on the quality of the data input, which requires the involvement of the architect and the MEP engineer. Once the information is collected the system will produce project comparative energy usage, demand and cost results over an average year.

When to create the Energy Model?

Energy modeling is most useful in the early stages of design. A proactive energy model allows architects, designers and engineers to create solutions rather than solve problems. Once the design of the building has been created in the energy model, it is relatively simple to compare various architectural and engineering energy conservation strategies. Project team members can evaluate preferred design options individually or in combination to determine the impact on energy and consumption and cost.   After each change, the modeler can evaluate the estimated energy use and cost to determine the combination of strategies and technologies will be most effective in reducing energy consumption. A similar approach can be taken with an existing building, but typically it is only useful to evaluate discrete energy conservation measures and not model an entire existing building. the value of an energy model reduces in relation to the stage of the building’s design – so start early!

 

Choosing the right modeler is a critical key to success! A talented energy modeler typically has experience in building engineering or architectural design and has analyzed many buildings. 

 

The modeling software must also be flexible and powerful enough to model various design scenarios with accuracy and speed. Through our experience, we prefer software that is based upon a DOE-2.2 simulation environment, like eQuest (available free-of-charge at http://www.doe2.com/).

 

The modeler should be selected for their ability to model appropriate building types and unique energy-saving systems, including daylighting, under floor air distribution, radiant cooling, thermal storage, renewable energy and demand control ventilation. The modeler must also be knowledgeable and comfortable working with members of the design team to help identify new energy-efficient solutions that will meet project goals.

 

Currently there are no federal requirements for energy models to verify compliance with building codes. While some states do mandate energy models for new buildings, Arizona is currently on a voluntary basis. This is probably something to look for in upcoming legislation in response to climate change.

 

In relation to LEED certification, a significant portion of potential points are devoted to energy efficiency (10 of the 69 possible points for New Construction). While an energy model is not required to meet the Minimum Energy Performance Prerequisite, Green Ideas has yet to find an owner that has pursued LEED certification for a new building without performing an energy model. 

 

For buildings over 20,000 SF it is necessary to complete an energy model under LEED-NC v2.2 to earn any of the ten points available under EA Credit 1: Optimize Energy Performance. Each point is awarded for increased energy efficiency relative to the ASHRAE 90.1-2004 baseline model.

 

An energy model is a powerful tool to help earn LEED certification, but more importantly, it is an indispensable tool for green building design. Energy modeling helps to maximize energy conservation, decrease environmental impact, and generate Life Cycle Cost savings that cover the expense of greening the building in the first place.