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How Do I Make Energy Models of My Buildings? Part II
Energy modeling interfaces help turn raw data into design. Part I of this two-part series covered simulation engines.
By Sara Fernández Cendón
There’s a conceptual shift underway in architecture today that’s as fundamental and powerful as Modernism’s complete rupture with the past. Architects and designers are beginning to think of buildings less in terms of how big they are and more about how they perform. In the automobile industry, consumers today don’t obsess over how big the trunk of a car is while ignoring its miles per gallon. Yet in the building design and construction field, the most common metric prospective homeowners worry about is square footage, and everything else (like how expensive a house will be to heat and cool) has been a lower priority.
To address and support this shift in thinking past first cost, architects and engineers have to be ready. Architects need to better understand how to use and process all the available data on how the buildings they design will function, including energy efficiency ratings, natural ventilation, water quality, etc.--all the contemporary metrics of sustainable architecture. To gather this data, architectural designers and design engineers are turning to energy models that can predict how their designs will perform when built.
In the world of energy modeling, there are two primary software types. First, there are the simulation engines—the “number crunchers,” covered in a previous issue of AIArchitect. Then there are the interfaces that connect users to the engines both through input and output mechanisms, discussed here.
It’s safe to say that most architects (except those with strong engineering expertise) might find direct use of any simulation engine currently available a bit daunting, and many would find even eQUEST and other available interfaces challenging.
“There are very few energy modeling programs that are even halfway through the process of developing an easier input style,” says Maurya McClintock, Assoc. AIA, director at McClintock Façade Consulting. “And the input style that they have developed so far makes it easier for engineers and energy modelers to create the input, but it’s nowhere near the level of ease of use that most architects are looking for.”
Though options at the moment might not give architects the ideal combination of comprehensive detail and ease of use, a few user interfaces seem to be headed in that direction.
Autodesk Green Building Studio (GBS), for example, is a Web-based service that uses the DOE-2.2 engine to do simple energy performance calculations. The program, which takes building geometry information from Revit, requires minimum additional user input and no special training in energy modeling. Outputs include estimated energy use and cost, carbon footprint, water and daylighting, preliminary analysis for LEED, as well as assessments of potential for renewable energy and natural ventilation. An annual subscription to this service for a single user is $745, with a free 30-day trial. The product is available free to Revit 2011 subscribers.
Late last year, Autodesk introduced Revit Conceptual Energy Analysis as part of Revit 2011. It’s a plug-in that allows users to perform energy analysis using GBS from within the Revit environment. Essentially, the plug-in allows users to create a model and submit energy analysis requests online, all without leaving Revit. The requests then go to GBS, which generates outputs in a colorful visual format and allows for side-by-side comparisons. Similar to this tool is Graphisoft EcoDesigner, which works within ArchiCAD to generate a graphical energy evaluation report, including energy consumption and carbon footprint information. All of these tools are best used as part of an iterative process in the conceptual and early-schematic design phases to refine decisions regarding site, shading, massing, glazing, daylighting, and the class of HVAC systems appropriate for the building.
For more advanced energy modeling, GBS generates files that can be imported into more complex tools, such as eQUEST (the DOE-2.2 engine interface), or even directly into other engines such as EnergyPlus. Working with these more sophisticated tools requires deeper engineering knowledge, and is often more appropriate during later phases in the design process.
There is a tool, however, that allows architects to work with EnergyPlus and take advantage of its more robust capabilities (as compared to DOE-2) early in the design process. OpenStudio, a free plug-in that connects the EnergyPlus engine with Google SketchUp, allows users to create and edit building geometry, launch EnergyPlus simulations and view the results, all without leaving SketchUp.
Another tool unrelated to the DOE-2 engines is IES, which also offers SketchUp connectivity through a free plug-in, available for Revit. The plug-in uses free software called VE-Ware to evaluate whole-building annual energy performance and track carbon emissions. The resulting simulations are limited, but they can provide early feedback in the design process. For more detailed analysis, IES has virtual environment (VE) tools that go from the conceptual to the advanced stages of design, starting at $400.
Other simplified tools that can be useful for architects during the early phases of design include Autodesk’s Ecotect Analysis ($2,995 for a standalone license). It offers analysis of factors such as solar radiation, visual impact, shadows and reflections, daylighting, shading design, and acoustic performance. And through access to the Web-based capabilities of GBS (which is free to Ecotect subscribers), Ecotect provides all GBS features, including whole-building energy analysis, carbon-emissions estimates, water-use and cost estimates, Energy Star scoring, and LEED daylighting credit potential.
On the immediate horizon is a full user interface for EnergyPlus currently in development. “The development of a user interface for EnergyPlus will make a big change in the industry within the next three years, because EnergyPlus is a more robust, more versatile public domain engine than DOE-2 is,” says Erin McConahey, a principal at Arup. “Some of the newer, more low-energy comfort-conditioning solutions [like] natural ventilation techniques can be better modeled for their actual energy usage because EnergyPlus algorithms actually do have the systems available for modeling, whereas before we had to fake it and mimic a system to be inputted like another system that was available in the software.”
Recently EnergyPlus has been the foundation of other more limited interfaces, some of which are still in development. One such interface is COMFEN, a program that analyzes commercial fenestration. McClintock says the advantage of these kinds of interfaces is that they still have the rigor of EnergyPlus calculations, but they default a lot of the input assumptions. “They are therefore much simpler tools that focus on allowing architects to compare some of the things they would be designing at the early stages, like the building envelope, glazing, and shading devices,” she says. “With these tools, they’re able to understand how their choices weigh against each other in terms of performance.”
Useful as these EnergyPlus user interfaces are for early performance comparisons, McClintock says they are not whole-building energy modeling tools because the mechanical and electrical systems are not part of the equation.
A continued interest in further integrating building energy modeling into BIM applications continues to drive development of energy models. In February, SMARTBIM, a leading analytics company that creates BIM product models and resources, announced its merger with ecoScorecard, which allows building professionals to search and evaluate products based on sustainable characteristics. The two companies hope to create a new business that will offer BIM objects that include embedded green building data—an important step in the continued effort to align information and modeling in BIM.
The merger has already resulted in specific plans for two new products. An ecoScorecard plugin for Google Sketch-up (free to download for a limited time), and a visual information modeling tool called VIMTrek. The ecoScorecard plugin allows designers to evaluate the environmental impact of products and materials in the model, and determine how they will perform in relationship to green rating systems. In the future, energy-specific data could be exported directly to energy modeling software. The VIMTrek program converts Revit drawings, BIM data, and ecoScorecard details into an immersive, interactive 3D environment where stakeholders can interact with the project as if moving through a video game. The program comes in two versions. The more complex version is called the Producer, and it converts Revit files into the visual information model file format, essentially creating the building environment. The simpler version is called the Viewer, and it only allows users to move around and make annotations within existing environments. The VIMTrek Viewer program is free and available for download. The Producer software, as well as an ecoScorecard Plugin for Autodesk Revit, will be available in December 2011. Pricing information on these two products is not available yet.
For architects to completely take control of how their buildings consume and create energy, it’s vital that energy modeling becomes as common and integrated into the design workflow as specification writing. Right now, there’s niche value in hiring energy modelers to help design buildings, but as the field advances, there is hope that it won’t be nearly so rarefied. Like sustainability before it, energy modeled design is just good design.
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Visit the AIA’s Energy Modeling Practitioner’s Guide website.
Check out the DESIGN: Art+Science video series trailer.
Visit the Committee on the Environment Web page on AIA KnowledgeNet.
Visit the Technology in Architectural Practice Web page on AIA KnowledgeNet.
Visit the AIA Sustainability Web page.
Visit the ICC’s International Green Construction Code Web page.
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