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comment Modeling Green
Engineers and Designers Still Discovering Sustainable Benefits of BIM
The industry continues to try to wrap its arms around what BIM means for green building.
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While building information modeling is fostering collaboration and improving efficiencies in sustainable design and construction, most experts across the A/E/C industry say it’s still a work in progress. Interoperability and process challenges must be resolved, many say, before BIM can achieve its full promise to help deliver healthy, resource-efficient facilities with reduced carbon footprints.
“You can talk about BIM or SIM [sustainable information modeling], but underlying it all is information modeling,” says Ken Hall, associate at San Francisco-based Gensler. “It is critical to have metrics that enable us to numerically assess the performance of our buildings from a sustainability point of view.”
In the past architects conceptualized and designed a building, then invited MEP consultants to determine how to heat and cool the facility, says Ken Sanders, Genlser’s chief information officer. “Now designers are thinking about ideas related to building orientation, exposure, daylighting and skin-to-floor ratios earlier.”
In the early stages of design, BIM is used as a geometric design tool to better understand the basic impact of decisions such as orientation and massing. “This is where BIM becomes so important because it gives us the ability to move geometry into analysis tools,” Hall says.
Information captured in BIM can be exported to energy and performance analysis software using standard data exchange formats, such as XML. “These early assessments are valuable because they help us to make decisions that we know will pay off down the road,” Sanders says.
As the design develops, analysis tools are used to examine glazing, façades, shading mechanisms and construction assembly options to optimize energy performance.
Structural engineers are leveraging BIM to optimize material usage and reduce the weight of buildings, says Erleen Hatfield, principal at New York-based Thornton Tomasetti. Different scenarios are easily created to determine how changes in a building’s height and footprint affect the curtain wall. “You can then automatically calculate the effect on cost, schedule or sustainability,” Hatfield adds.
But truly realizing the benefits of BIM goes beyond implementing the software. “There is a process transformationthat needs to accompany the software,” Sanders says. “All the people involved in the project, including the engineering consultants, need to be engaged early on in conceptual design when you are addressing issues related to energy, carbon and sustainability.”
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| Paul Seletsky, senior manager for digital design, at Skidmore, Owings & Merrill LLP, New York. says designers could better assess carbon footprints by using life-cycle information. |
LEED criteria most easily reported out of a model relate to materials, areas and quantities, Hall says. Reports can look at the area covered by green roofing materials or site coverage of indigenous plants.
Other data, such as recycled content, require developing more detailed information from scratch. “But once our ‘green tracking’ processes are formalized, they will be embedded in BIM protocols documents to be used on our other projects,” Mallie adds.
Tracking a wider array of LEED characteristics will require linking the models to lifecycle assessment tools, says Paul Seletsky, senior manager for digital design at Skidmore, Owings & Merrill LLP, New York. Using life-cycle information, designers could select different materials and assess carbon footprints.
Sustainable Construction Management Construction teams embracing BIM, along with virtual design and construction software, are discovering that the tools enable sustainable construction management.
For example, SHoP Construction is providing virtual integration services for the renovation of 60,000 sq ft in the Fashion Institute of Technology’s A-Building in Manhattan to create studios, classrooms and labs. Working with key trade contractors, SHoP is continually updating and coordinating the project’s BIM models to facilitate construction.
“The VDC process addresses the inefficiencies inherent of typical traditional approaches to project delivery,” Mallie says. “Through the limitation of change orders and ‘comebacks,’ waste is significantly reduced as well.”
At Columbia University, Turner Construction, New York, is managing the construction of a 14-story, 188,000-sq-ft science building. Steel, mechanical,electrical, plumbing and fire protection trade subcontractors provided models that Turner merged with the architect’s model to create a Master Consolidated BIM for the $230-million project.
Subcontractors on the job have benefited from using BIM to coordinate their work on a daily basis with other trades in 3D, says James Barrett, Turner’s national manager of virtual construction technologies. “It dramatically reduced ‘hits’ in the field, which makes them more productive and faster in completing the work,” Barrett says. “Waste is reduced from inaccurate ordering, field fabrication or install/re-install cycles when they come into conflict with other trades.”
Structural steel, HVAC, plumbing and some electrical contractors on the project are using model data to automate their fabrication process. “By prefabricating systems or sections of systems offsite, you have less cutting and work in the field, which by default is less productive,” Barrett says.
Hatfield says he is starting to see the façade industry using BIM to prefabricate curtain walls and metal panels. “If we create the BIM model with enoughsophistication, fabricators can access and use the data,” he adds. “For sophisticated facades, data may need to be extracted and imported into a façade modeling package and then delivered to the manufacturers.”
“Major MEP subcontractors working with Turner are reporting 15 to 30% less materials waste when Turner implements our Virtual Trade Coordination process on a project,” Barrett says. “We are trained to track the waste we create and what we do with that waste. With BIM you fundamentally avoid creating it in the first place. Given those benefits I would make the proposition that a BIM job is a green job.”
Future Developments Barrett sees a tremendous opportunity in using BIM/VDC tools to retrofit existing buildings. Mayor Michael Bloomberg’s PLANYC 2030 estimates that 85% of the buildings that will exist in 2030 are already built. “If you are going to have a dramatic impact on reducing the carbon footprint by 30% in 2030 [as advocated in mayor’s plan], you have to look at existing buildings,” Barrett adds.
BIM in conjunction with analysis software can create “what-if” scenarios to compare baseline operating cost of an existing building with the operating costs after retrofitting the building with new windows, additional insulation or upgraded equipment and systems, Barrett says. Combining modeling information with cost of the equipment and construction will produce life-cycle studies and payback analyses of various options, he adds.
Another opportunity lies in integrating BIM with facility management systems to help clients manage their buildings. “Since BIM is a database-centric tool, it can talk to other databases,” Barrett says. “That is exactly what we are looking at right now. How do we use the database and the great information in the database for other purposes, such as talking to facility management systems?”
Major BIM vendors are working on interoperability standards and are acquiring analysis software with an eye toward developing integrated suites of services. But even within its own suites of products, vendors face interoperability challenges, Genlser’s Sanders says.
Skidmore, Owings & Merrill’s Seletsky says a transfer protocol is needed that allows two-way communications between BIM and the analysis tool. “I can do an analysis of my Revit [BIM] model using Ecotect [energy analysis tool], but what I can’t do is shoot the information back in the other direction,” he adds. “I can’t apply certain constraints in Ecotect and see what the resulting geometry or BIM model is going to be.”
Beyond interoperability, firms are developing guidance to help teams make smart sustainable design decisions using BIM. “People tend to over model or over analyze things too early, when it is not informing the design process,” Sanders says. “It all gets back to how you marry a process to the new technology and tools.”
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