Editor's note: The following article is based on the session “Sustainable Design and Energy Retrofits: A Collaborative Digital Workflow,” presented by the authors during HPAC Engineering's sixth annual Engineering Green Buildings (EGB) Conference and Expo, held Sept. 24 and 25 in Nashville, Tenn., part of HVACR Week 2009. HPAC Engineering is accepting proposals for sessions for EGB 2010, to be held Sept. 23 and 24 in Baltimore. For more information, contact Executive Editor Scott Arnold at 216-931-9980 or [email protected].
Contrary to popular belief, automobiles and other forms of transportation are not the root of the energy crisis; buildings are. According to the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy,1 buildings account for 72 percent of U.S. electricity consumption, 40 percent of U.S. carbon-dioxide (CO2) emissions, and 9 percent of total global CO2 emissions. With research2 showing that more than half of the commercial buildings built prior to 1980 (when energy codes largely did not exist) have yet to undergo any type of energy-related renovation, retrofits represent an enormous opportunity to reduce building energy consumption.
The dilemma we face is deciding how best to upgrade buildings. This article will discuss how building information modeling (BIM) is enabling building professionals to review entire inventories of buildings and prioritize funding for renovations and retrofits to provide the greatest return on investment.
The best design processes are collaborative ones, in which owners, architects, engineers, and contractors work together to explore and develop solutions. Technologies such as laser scanning and BIM enable more effective collaboration and have become the backbone of a new, digital workflow. With design modeling and analysis tools, design teams can make more-informed decisions earlier in the design process, increasing the likelihood of their delivering projects on time and on budget and with minimal environmental impact.
For energy retrofits, this digital workflow consists of three major stages: information gathering and input, modeling and visualization, and simulation and analysis.
Information gathering and input
With traditional methods of modeling from paper drawings and field surveys often not quick or cost-effective enough to meet a client's needs, two alternate workflows have emerged: photographic capture of existing conditions and laser scanning. Which technique is used often depends on the intended next steps.
If an owner has a portfolio of dozens of buildings, photographic capture of existing conditions could be the best first step in comparing and prioritizing possible energy retrofits. With this method, multiple photographs of all of the facades and the roof of a building are taken. By identifying common points in the photographs, a computer determines the geometry of the building and creates a simple model. This technique also can be used for the interior of a building. More-detailed measurements of the building may be required at the point construction documents are prepared; certainly, they will be required prior to fabrication.
Laser scanning is the more common method, especially for buildings that are historic, geometrically complex, and/or expected to undergo significant renovation or construction. Laser scanning involves precision instruments making 360-degree measurements that, when aggregated with other scans, create an extremely accurate representation in the form of a point cloud. Laser scanning replaces typical site and field surveys and often can reveal discrepancies, such as squareness or levelness, not easily identified by other means. The accuracy of this technique often is suitable for construction documents and prefabrication.
Combining new modeling and imaging technologies with more traditional methods of analysis can enable a project team to paint a more accurate picture of what is happening in a building and better determine the areas with the greatest potential for energy savings. That is the case in Katy, Texas, where typical load-calculation software is being used with BIM in the design of a hospital expansion.
Modeling and visualization
When communicating with the rest of a project team — the building owner in particular — visualization is key. Using a building information model to show how certain design strategies or operational changes can lead to considerable energy savings enables more-informed decisions. Visualizing data and analysis results makes payback easier for owners to grasp and gets them on board earlier in the design process. BIM takes the guesswork out of making important decisions related to a building's operation and efficiency.
Beyond energy analysis, the value of a building information model is its ability to evolve throughout design and into the construction phase, serving as a data repository and tool for visual communication. Not only does BIM enable engineers to better inform building owners, it fosters collaboration among members of a project team. On a recent project in Fort Worth, Texas, BIM was used to help the project team, including the architect and structural engineer, identify potential issues prior to construction.
Simulation and analysis
The primary advantage of BIM is the ability to look at a building holistically. Take, for example, daylighting. With a simple analysis of window locations, window properties, room shapes and functions, building orientation, and window shading, the potential for energy savings can be determined. This analysis can be performed easily in a three-dimensional graphical environment and used to explain to a building owner options that are available and how those options would impact the quality of a building's interior environment.
A digital workflow allows all of the individuals involved in design to collaborate and understand opportunities for improvement. Ultimately, it allows an owner to prioritize and maximize energy improvements. The integration of typical load-calculation software with a building model enables more-accurate analysis with fewer assumptions. Likewise, a number of different design or control strategies can be modeled to allow a building owner to maximize energy savings while staying within budget.
Improving the energy efficiency of buildings will go further toward ensuring a truly sustainable future than any other activity or mandate. If owners see how projects to improve sustainability can improve their bottom lines, energy-saving retrofits and sustainable design will become more of a priority and less of an afterthought.
- EERE. (2008). Energy efficiency trends in residential and commercial buildings. Washington, DC: U.S. Department of Energy. Retrieved from http://apps1.eere.energy.gov/buildings/publications/pdfs/corporate/bt_stateindustry.pdf
- EIA. (2003). Commercial buildings energy consumption survey. Washington, DC: Energy Information Administration.
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An industry-programs manager for Autodesk Inc., developer of two- and three-dimensional design software for the manufacturing, building and construction, and media and entertainment markets, Robert E. Middlebrooks, AIA, specializes in building-information modeling (BIM), integrated-project-delivery adoption, and industry relations. During 26-plus years as an architect, he has been involved in projects around the world, including collaborative design-build and developer-led integrated projects; led digital design efforts; and overseen the implementation of full-discipline BIM. Lorisa L. Behrens, LEED AP, is a mechanical engineer in training for Smith Seckman Reid Inc., an engineering design and facility consulting firm with more than 500 employees in 13 offices across the United States. Specializing in the use of BIM for HVAC-systems design, she is involved in the design of a 370,000-sq-ft hospital expansion and retrofit in Texas.