Using BIM to Optimize the Building Envelope

“Building Information Modeling (BIM) technology is a software-based approach to building design that incorporates 3D data, performance data and more,” says Forrest R. Lott, FAIA, LEED-AP, principal of Savannah, Ga.-based Lott+Barber. “In fact, it can include such factors as time and sequence of construction — just about any type of information you can think of can be associated with the model.”

To be sure, BIM is not new technology. It is, however, just now “rising to the consciousness of a substantial number of people,” says Finith E. Jernigan, AIA, president of Salisbury, Md.-based Design Atlantic Ltd.

Perhaps that’s because of its ability to easily transfer information, instead of recreate it, at each stage of the building process. Perhaps it’s because of its ability to give accurate information in real time. “For us, the information is the most important,” confirms Lott. “The ability to attach information is where the real power comes in.”

And perhaps BIM is coming into its own because of its ability to optimize the building envelope to achieve high-performance buildings. Design Atlantic uses BIM, and “optimizing the building has been our bread and butter for a long time,” notes Jernigan.

Research Allows for Better Design
Purchasing and using BIM software does not automatically make an architect an expert in building design, much less in optimizing the building envelope. Enter the professionals at RTKL Associates, who made a conscious decision in 2003 to transition to BIM from a CAD-based design process. The firm’s software of choice is Revit.

“Using BIM gives us an increased efficiency in our workload,” says Douglas Palladino, AIA, principal in the Washington office. “Because it automates the repetition and coordination of items, it has freed us to do the analyses we want to do, which allows us to increase energy efficiency.”

Two years ago, RTKL purchased Ecotect (to which geometric information from Revit is transferred), a 3D modeling tool that analyzes buildings for sustainability attributes. Shortly thereafter, Hiroshi Jacobs, AIA, LEED-AP, an RTKL associate, embarked on a yearlong research project to learn how to use Ecotect to improve design efficiency. He was partnered with a mechanical engineer. “The purpose of the project was to make Ecotect an integral part of the design process on all of our projects,” he says.

Jacob’s research shows that four analyses from Ecotect, performed in the early stages of design, provide the ability to increase energy efficiency. They are psychrometric, passive design, shading and solar radiation.

“These analyses are tools, similar to a paintbrush, paint and paper,” says Palladino. “You use the tools to create a watercolor, and the first one is not quite the way you’d like it to be. The tools wield an enormous amount of power, but it takes time to develop the technique of how best to use them to get the results you want.

“When you first start using BIM and analytical tools, you’re doing a watercolor painting, but you may not be making art. You have to develop the technique to take full advantage of the tools. That’s what Jacob’s research was about — how best to use the tools.”

Jacobs admits that, using BIM, the design process gets complicated as you think about how the tools connect to each other. “We have to make decisions about what information gets transferred between the tools, how much and at what point in the design process,” he explains. “We had all the tools and were using them to varying extents in projects, but we wanted to understand the best way to transfer the information and at what time both on the architectural and MEP side.”

In performing these analyses, the architects are not looking for absolute values. They are looking to compare different options. “With these analyses, we can show owners long-term consequences of different options, allowing them to be partners in the decision-making process in ways that were virtually impossible before,” says Palladino.

A Perfect Partnership
Ecotect is only one of a number of plug-ins that assist BIM users with creating high-performance buildings. IES’ Virtual Environment does things like bulk sizing of equipment, producing different options of zoning for mechanical layouts and generating heating/cooling demands quickly. “It’s a trusted analysis engine that has been used in Europe for a long time,” says Jacobs. “Energy+, developed by the U.S. Department of Energy, is also starting to be used. It uses a base analysis engine, on which almost all of the energy analysis programs are based, to produce a thermal simulation of how a building will perform.”

With the BIM plug-ins, and knowledge of when to use them in the design process, energy efficiency is predictable. “Previously,” says Palladino, “the decision of which type of roof to use would be made from experience, intuition and just a guess and a hope that it would be the appropriate one. Now we can confirm our intuition or prove that maybe we were wrong. What generally turns out to be the case is that our intuition was correct, but there’s fine tuning that we could never have known.”

Ultimately, BIM does not allow architects to design more quickly or less expensively. It does allow them to design better. “That’s what we’re after,” says Jacobs. “We use the time we gain to make the design better.”

Lott agrees, noting that BIM is amazing and makes design fun: “Because it’s so detailed,” he says, “we can collect all of the thermal performance information and data about a building’s glazing, skin and roof. In glazing alone, we can look at solar heat gain, U-value, how much visible light will get through, how much shading will get through and more.”

Does the ability to create high-performance buildings draw clients to architects who use BIM? In some cases, yes. But, mostly, says Jernigan, clients who know about BIM grab onto the ability to get more certainty about what their project is, including design and energy efficiency. BIM + architects + clients = a perfect partnership.

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