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!
Who Should Perform the Energy Model?
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.
In March of 2007 the United Nations Environmental Program released the reportBuildings and Climate Change, stating 30-40% of energy worldwide is consumed in what is known as the Life-Cycle (the design, construction, operation and demolition) of a building. This report confirms what many of us in the green building industry already understand; addressing the energy use of the built environment could have the single greatest impact in reducing our energy demands as a society and therefore the negative effects on our environment, economy and well-being.
Of all the stages in the Life-Cycle of a building, the energy used in the operation phase has the greatest environmental impact. Accordingly focusing on this consumption is extremely effective in reducing a building’s overall consumption, yet determining energy use in a building’s operation phase is not always an intuitive process for even the most experienced designers.
In our efforts to reduce operation phase energy use for our clients Green Ideas has found energy modeling as an indispensable design tool and has therefore integrated energy modeling into our service offerings. Energy modeling can help project team members evaluate a variety of energy conservation measures with little resource allocation to determine optimum strategies that maximize both energy and cost efficiency.
Energy Modeler’s role on the Project Team
Green Ideas has significant experience with computer energy modeling to meet LEED and ASHRAE 90.1 Standard requirements. Energy modeling services can either be performed in-house or by our energy modeling partner, Quest Energy Group.
The Energy Modeler’s role in a project requires a close working relationship with the architect, lighting and mechanical designers throughout the design process to ensure an integrated building design. This approach facilitates critical decision-making regarding the impacts of the building envelope, the daylighting and interior lighting systems and the size of the heating, ventilation and cooling equipment. Accordingly, the Energy Modeler’s initial project involvement will occur during the schematic and early design development phase of the project to produce maximum impact. Green Ideas recommends performing energy analysis early enough in the design process to help the design team make design decisions that will affect energy consumption and comfort.
Schematic Design Phase
During the Schematic Design phase, the Energy Modeler will attend a kick off meeting or design charrette with the owner and design team to develop a preliminary list of energy efficiency measures (EEMs) and HVAC system alternatives that will be evaluated for the project. These EEMs typically include alternatives for wall and roof construction, window type and location, natural daylighting opportunities, high-efficiency package unitary equipment, etc.
The Energy Modeler will then develop an hourly computer model of the schematic design using the eQuest software program. Using this model, Green Ideas will develop a minimally compliant (ASHRAE 90.1) model of the facility. This baseline model will serve as the basis for evaluating potential energy efficiency measures and system alternatives. It will also be the basis for determining the number of credits available under LEED EA Credit 1: Optimize Energy Performance. A second meeting will be scheduled with the design team to present the results of the preliminary analysis. The Energy Modeler will provide the design team with the expected overall performance of the facility as well the economic viability (simple payback and life-cycle cost) of each of the energy efficiency opportunities.
Construction Document Phase
At the end of Construction Document phase, the Energy Modeler will reconcile the computer model of the facility to reflect the final building design. At this time, the Energy Modeler will complete the LEED documentation for both EA Prerequisite 2 and EA Credit 1. A final wrap up meeting or conference call will then be scheduled with the design team to share the results.