GreenBuilding Information Modeling
As construction growth intersects with environmental concerns and the rising cost of energy, the concept of sustainable design—drafting, specifying, building, and operating structures to minimize their ecological impact—green building solutions — are gaining ground. In a 2003 survey, one-third of firms said they were working on sustainable-design projects, and this number has likely increased.1
Although green building remains an admirable goal, it is not always easy to achieve. Depending on building techniques and strategies selected, long-term gains and short-term costs all too frequently collide in a tight economy. Additionally, the sheer volume of documentation—from two-dimensional paper drawings to spreadsheets of engineering data—yields a primordial soup of information that needs a spark to bring sustainable design options to life.
The concept of building information modeling (BIM) could be the ‘big bang’ needed for green building. Embraced by architects/engineers (A/Es) seeking higher quality designs and more productive collaboration, the technology can help harness the characteristics and performance of design concepts, allowing A/Es to compare sustainable alternatives to balance energy and resource efficiency with project costs.
Growth of green building design
Interest in sustainable building design has increased the need for solutions for energy conservation, alternative energy sources, and design for greater efficiency popularized in the last 30 years. Initiatives put forth by the U.S. Green Building Council (USGBC) are now part of its Leadership in Energy and Environmental Design® (LEED®) rating system. LEED certification has been suggested by many federal, state, and local agencies for sustainable design comprising site, indoor environmental quality (IEQ), and efficient use of energy, water, and materials.
USGBC membership has grown in the past years, and San Francisco, California, and Boston, Massachusetts, have most recently joined those cities requiring public-owned projects achieve at least a LEED Silver rating. The impact on the building industry is evident. USGBC estimates green building is now a $1.4 billion market. The LEED certification standard is expanding, with similar efforts appearing both within the United States and abroad.2
Today, designing sustainable buildings requires intensive effort in the early stages of project development as A/Es learn new approaches. However, as those designers gain the analytical skills necessary to work green, these approaches will be integrated into their standard services, and the parameters governing project cost will change accordingly. Today’s relentless focus on short-term, first costs of construction will likely give way to life-cycle cost analysis (LCA) that reflects the savings and benefits of sustainable building design.
Even when a design team is willing to try a sustainable approach, other factors come into play—namely, the difference in tools and technology used by each discipline. Architects employ drafting technology to define their work graphically, while engineers tend to define specifications using word processing and spreadsheet tools. The simple act of communication is burdened by the absence of a shared language or common tools for conveying concepts.
Building information modeling is a new approach to building design, construction, and management. It is characterized by the continuous and immediate availability of internally consistent and reliable information about the project. Transcending the pure geometry of conventional two-dimensional, graphics-based design, BIM offers a parametric database of design information—a digital representation of a building that reflects the project scope, schedule, and cost information consistently throughout the development process. This ensures:
- reliable, consistent information about the building is available digitally to support various analyses required for sustainable design;
- drawings are integrated with project data—from engineering performance analysis to materials specifications—so the building’s digital representation reflects its properties and performance; and
- parametric modeling, which defines relationships among building elements, making it possible to change one aspect and see/understand its impact on related design and performance characteristics.
The effects of building information modeling include greater insight, easier visualization, improved analysis and greater control over cost, sourcing, and specification, down to the precise materials and design determined to deliver specific energy efficiencies, indoor air quality (IAQ), and sustainable performance. A design created using BIM yields not only traditional design deliverables, but also a context for making decisions, including sustainable design strategies.
Optimize green designs
Prior to the housing boom, the U.S. Environmental Protection Agency (EPA) estimates new residential construction generated 5.95 million metric tonnes (t) (6.56 million tons) of waste annually.3 Certainly, residential construction in the United States is very efficient because it is based on the availability of standard building components (such as framing timber) milled in a few standard lengths and very effectively produced and shipped. However, in many cases, efficiency can end here.
During the building process, tons of construction waste can result from the assembly of the traditional framing, as material is cut from standard lengths to fit local conditions. Standard roll-milled carpet is extensively cut to fit each installation. The scraps can wind up in landfill. In a typical year, more than 1.8 t (2 tons) of carpet are discarded in the United States, of which only about one percent is recycled.4 Gypsum wallboard alone accounts for 15 to 30 percent of new construction waste volume.5
Other industries, such as manufacturing, have solved these problems by using technology to simulate new products to optimize assembly and material use, thereby minimizing waste. For the building industry, digital modeling is a powerful opportunity to understand, explain, and modify designs for optimal performance and minimal waste.
Today’s graphic CAD tools fail to capture or represent the data required for performance analysis, and the resulting paper deliverables support such a process. Engineers must perform ‘takeoffs,’ that is, manual measurements of graphical components that must be entered into a database or software application purpose-built for evaluation. Building models working in concert with analysis tools can eliminate this inefficient step and make evaluating sustainable alternatives easy. Initial and then more refined models can be archived and accessed to compare schematic, developing, and construction documents over the course of a project. A/Es can study and track the impact of building and system design changes as they work, optimizing designs as the project progresses.
For the rehabilitation of a financial services customer’s 14-story headquarters in Charlotte, North Carolina, Little Diversified Architectural Consulting used building information modeling to develop and study a range of design options and understand the effects of daylighting (Figure 1, page XX). The firm revisited these scenarios at the schematic, development, and construction document phases to compare alternatives as design progressed. This enabled them to choose the best solution, without duplicating work or over-documenting concepts.
Visualizing building structure, materials, performance
Just as important as design optimization is BIM’s ability to present sustainable options—and the complex calculations and analysis behind them—in an intuitive fashion. The advantages start when the extended team—including architects, engineers, client, and contractors—convene to collaborate on project goals and initial building characteristics.
A project depicted with a building information model produces a cohesive view of features and function in an intuitive format everyone can understand and manipulate. Design features and specifications for materials and surfaces are wed with real performance measurements for energy load, indoor air quality (IAQ), light efficiency, and so forth. As the project evolves, the model can be refined with new analysis and new design alternatives, to provide near real-time insight into the end result.
Thus, the A/E can study very specific changes in relation to decisions that, once built, cannot be reversed (e.g. building siting). With insight into the effects of the environment and the elements—from sun, wind, and rain to surrounding structures—the building team can quantify the most effective options before construction begins and changes are no longer possible.
With greater visualization capabilities, building teams can more easily show clients the benefits of different sustainable-design choices. Virtual walkthroughs of the building model allow owners to see the effects of green design. In using BIM, Little was better able to demonstrate options for reducing exterior light pollution at a project designed for the University of North Carolina (UNC). This was one of the conditions—along with improving interior comfort and energy efficiency—specified for the renovation of a 1960s dormitory into a modern residence hall on the Chapel Hill campus. The task of reducing light pollution had to balance the need for sufficient lighting to provide security. The architects used BIM to gauge whether design options met specified sustainability criteria, analyze the effects of custom lighting fixtures and façade design, and present all these proposals in a format that made it easy for UNC to approve designs.
Little also relied on BIM to explore options for maximizing daylight penetration into the residence hall. The U.S. Department of Energy’s (DoE’s) Energy Efficiency and Renewable Energy Network’s Center of Excellence for Sustainable Development estimates commercial and residential buildings consume 70 percent of electricity generated in the country. By harnessing daylight through strategic design of the building exterior, A/Es can sharply reduce not only electrical load, but also heat and energy loads created by lighting.
As daylight analysis is an especially complex undertaking, modeling typically requires the help of experts or specialized laboratories dedicated to this aspect of design. As a result, daylighting studies are not conducted regularly, despite the significant impact they may have on a building’s performance. Design teams equipped with tools for BIM can make short work of analysis and documentation of interior daylighting effects to optimize energy consumption.
Project architects at Little also used BIM to evaluate daylighting as part of its proposal for an innovative complex at the University of South Carolina/Columbia. Intended to exemplify the impact and benefits of sustainable design, the project incorporates features such as subterranean construction and a green roof, while serving the university with housing for 500 students, assembly rooms, classrooms, and offices (Figure 3, page XX).
Following its use of BIM in the planning stage for site selection and orientation to maximize natural lighting and energy conservation, the team used BIM to design the structure, maximizing interior daylighting and capitalizing on exterior bounce light between buildings. Among other advantages, the completed building has been submitted for LEED Gold certification—it uses 45 percent less energy than a typical construction project, and costs no more to build than a conventional structure.
Assessing energy performance
It can be staggering to think commercial and residential buildings—81 million structures in the United States—account for about 40 percent of total energy use (compared to sport utility vehicles [SUVs], mini-vans, and light-duty trucks, which use seven percent).6 Until now, the complexity of energy analysis has relegated the process to an infrequent exercise used primarily for load sizing. Without this crucial information, sustainable design efforts and decisions clearly suffer. However, BIM can integrate building models with energy analysis tools for accurate, routine evaluation based on geometrically correct thermal models, local building code requirements, and DoE models.
For a psychiatric services center in New York City, an architecture firm was charged with design and construction to LEED rating requirements within the original budget parameters. Instead of losing time and incurring expense for engineering consultants to redraw the building and model baseline performance and incremental efficiency levels for energy use, the architects used BIM to test, reconfigure, and re-test building performance, before sharing the results with systems engineers to develop a final design.
Buildings use 40 percent of raw materials globally—an annual total of 2.72 billion t (2.99 billion tons), according to a report prepared for Worldwatch Institute.7 The extraordinary amount of waste—123 million t (135.6 million tons)—associated with construction and remodeling has made accuracy in estimating materials an extremely urgent aspect of sustainable building. This has also made reuse and recycling, local and renewable sourcing, and phased assessment of demolition and construction key requirements for green building certification.
A project designed with BIM incorporates all project data related to materials and their relevant characteristics, which can be documented according to LEED requirements. Furthermore, by capturing updates to the condition of materials, BIM enables the building team to track and report the status of demolition and construction on a project. Periodic calculation of volume and area based on the project phase can help determine the quantity of material required for structural, shell, and interior construction.
Last-minute changes, usually made in the name of cost control, can undermine the design intent of a project by substituting or replacing materials or fixtures with elements that perform differently. Since BIM captures both design and engineering data, materials and building components can be specified precisely according to plan and alternatives evaluated accordingly, eliminating misinterpretation and incorrect changes.
With the power to create relation and order among design, engineering, scope, and budget data, BIM transforms information into a meaningful, functional representation of all building elements. According to experts, much could be accomplished in the next 10 years, due in part to BIM tools enabling more green building, including:
- saving enough energy to power over one million new homes for one year;
- saving in excess of $4 billion in electricity costs;
- reducing the need for more than 175 power plants, thus saving the $8.5 billion required to build them; and
- reducing carbon dioxide (CO2) emissions equivalent to removing over one million SUVs from the road (the American Gas Association).8
BIM’s integrated model and singular approach to green building stands to transform an industry poised for change. Aspects of design and construction cause nearly a third of
U.S. construction dollars to be spent on mistakes, inefficiencies, and delays.9 BIM introduces an unprecedented measure of design precision that benefits both the environment and the building industry itself.
About the Author
Phillip G. Bernstein, FAIA, LEED AP, has served as a lecturer in professional practice at the Yale University School of Architecture (New Haven, Connecticut) since 1988. He is vice president for Building Solutions at Autodesk Inc., where he is responsible for setting the future direction of technology solutions for the building industry. A practicing architect with 20 years of experience, Bernstein was formerly an associate principal at Cesar Pelli & Associates. He can be contacted at Philip.firstname.lastname@example.org.
1 Building Design & Construction White Paper Survey, Reed Research Group (September 2003).
2For a deeper look at the current state of LEED, see “Understanding the Marketplace for Green Buildings and Green Building Products—2004 update” by Jerry Yudelson, PE, MBA, in the January 2005 issue of The Construction Specifier.
3 Franklin Associates. Characterization of Building-related Construction and Demolition Debris in the st1:country-region>United States.U.S. Environmental Protection Agency Municipal and Industrial Solid Waste Division, Office of Solid Waste (1998).
4 Fishbein, Bette K. “Carpet Take-Back: EPR American Style,” Environmental Quality Management (Autumn 2000).
5 Johnston, Hal, and William R. Mincks. Waste Management for the Construction Manager, American Association of Cost Engineers (1992).
6 Mazria, E. “It’s the Architecture, Stupid!” Solar Today (May/June 2003).
7 Lenssen and Roodman. Worldwatch Paper 124: A Building Revolution: How Ecology and Health Concerns are Transforming Construction, Worldwatch Institute (1995).
8 “New Wiring,” The Economist (January 2000).
9 Projections determined by GeoPraxis using the following: (1) new home sales data compiled from the U.S. Census Bureau, (2) energy demand forecast data and energy price data from the U.S. Department of Energy, (3) power plant emission data from the U.S. Environmental Protection Agency (EPA), (4) light truck emission data from the Energy Information Administration, and (5) averaged power plant construction estimates from the DoE.