Building Design

BIM and Sustainable Design, Part 2

18 Jul, 2007 By: Heather Livingston

Design software companies use different approaches to reach the same goal.

Last month, I talked with Renee Cheng, AIA, head of the School of Architecture at the University of Minnesota to better understand the current state of integration between building information modeling (BIM) systems and sustainable design. This month, I’m looking the practical differences between sustainable design platforms offered by Autodesk, Bentley, and Graphisoft.

When asked about Autodesk's recent initiatives, Jay Bhatt, senior vice-president of AEC Solutions, said, “One of the critical directions we’re taking with our products across product platforms is around sustainable design. The best way to see sustainable design from my perspective is the creation of something that can be simulated effectively for the factors that contribute to energy conservation and energy efficiency around the building footprint. The only way to simulate and run the analysis to make sure the building’s going to perform in a sustainable, green way is to utilize data to run analysis processes.”

Instead of trying to create a BIM application based on its AutoCAD technology, Autodesk purchased the Revit product about five years ago. The parametric program allows the user to input information in the data cells and then link them, much like Microsoft Excel.

“We made a big acquisition and we paid a lot of money to buy this technology to be fundamentally different than anything else in the industry that we saw,” Bhatt said. “We were not going to go about reconstructing and classifying and rebranding our older technology to say it was BIM: to sort of wave our magic wand and say the AutoCAD-based products are building information modeling tools. We didn’t want to do that because we thought it was disingenuous and we didn’t think it was accurate based on what we thought the proper definition of what BIM is.”

So what is BIM according to Autodesk? Bhatt defined it with what he calls the “three Cs” of BIM: consistent, coordinated, and computable. It has to be consistent and something you can count on. The coordinated piece is very important for sustainable design because all of the participants in the design process have to come together in a coordinated way to create a true sustainable building. An architect can’t create an efficient representation of a building if the HVAC engineer comes in and designs an inefficient heating or cooling ventilation system. Today, the industry manually coordinates everything through paper-based blueprints and documents. Revit provides modules that make it simpler for all players to work together: Revit Architecture, Revit MEP, and Revit Structure. The Revit platform supports all of the disciplines, so the MEP engineer can coordinate with the architect, with both players inputting and storing information that works together and goes through the same analytical processes that support sustainable design.

Bhatt said the computable element is important for sustainable design because until you can use the data to run computational analysis, it isn’t possible to create a true simulated sustainable experience. Revit allows the user to input information into a database that forms a representation of the design. Its data-driven design, with data underneath the graphical and visual representation of the design, can be used for many different purposes. He explained that without a database-oriented design process, the architect is left with the old way of doing things and won’t really be able to understand how a three-story residence, office building, or hotel is going to perform in its lifecycle because a quantitative simulated analysis on the data set can’t be accurately performed.

To gauge sustainability and energy usage on a building design, Revit takes a threefold approach. It relies on outside partners such as IES to conduct computational energy analysis. In the Revit product itself, Bhatt said Autodesk is building, where appropriate, internal mechanisms to do analysis and simulation inside the application. Finally, Autodesk offers complimentary products that provide visualization and simulation for sustainability such as 3ds Max, a three-dimensional tool that allows designers to put CAD and BIM designs into an animation and visualization tool for analysis and evaluation.

To get Bentley’s take on the subject, I talked to Huw Roberts, global marketing director for the Building Group at Bentley. “BIM is all about having a better understanding of your building before you build,” Roberts said. “It helps you have a better design process and understanding of the building’s performance, including how it performs from an energy point of view.” Roberts believes that BIM allows designers to see the implications of their decisions and find the best solution, and it allows them to focus more of their energy on the design activities rather than the documentation activities.

He also believes that a big difference and advantage that Bentley offers over competitors is that their BIM solution is integrated and multidisciplinary, so architectural, mechanical, electrical, site, civil, and infrastructure work together, and the information and the components within those different disciplines can interact. In sustainability, things like insulation values, solar loads, air movement, and lighting values require technical, numeric-based analyses that optimize the system, and those all work together because all of the systems involve multiple disciplines.

Bentley also provides a more complete understanding of the building’s performance, Roberts said, allowing innovative approaches to sustainable design. An example he cites is the Morphosis-designed San Francisco Federal Building. Morphosis, a long-time Bentley Architecture client, used the application to create the first tall building in the United States built without air conditioning in the tower since the introduction of air conditioning systems. They were able to gain a “holistic” understanding of the tower and incorporate mechanical solar shades that adapted to time of day, sun location, and weather through sensors placed in the building and a double-layer skin that established a convection pattern to get natural ventilation and air movement through the building. “That kind of holistic approach is really only possible because you can simulate the whole building and any of those systems in it in a multidisciplinary BIM environment,” he explained.

To run sustainability analyses, Bentley ties into EnergyPlus, Trace700, and IES. They also are working on Green Building Studio, GBxml, which is in beta and will be released soon. Roberts notes where Bentley’s integration is unique is on the fabrication side where it links to manufacturers’ catalogs. So, for example, when using Bentley Electrical or Mechanical, the designer can choose a light fixture or fan unit or chiller that will come into the model with all of its energy information such as how much power it needs and how much cooling it provides, tying into the analysis immediately.

Roberts also says that the system includes analysis capability for things like solar load, sun penetration, natural daylighting, and more. “That’s built into our system and it works with that electrical lighting, so you can blend those two together,” he said. “We can go to external analysis for that as well, but you can also just do it right inside the system.”

Graphisoft’s approach relies largely on working with a variety of partners in sustainability, said Patrick Mays, the company’s vice-president for North America. The company's ArchiCAD BIM program links with EnergyPlus, Green Building Studio, Ecotect, ArchiPhysik, and Riuska. “Our key partners here are Green Building Studio and Ecotect, [which are] focused on the architectural market because we feel like more complicated products like EnergyPlus are more often used by engineers than by architects,” Mays explained.

“Our methodology is to create zones within ArchiCAD and then export the simplified energy model into Ecotect using Green Building Studio’s gbXML format,” he said. There, the energy analysis and solar design is completed. From Ecotect, designers connect to other products like DOE-2, EnergyPlus, or other applications. Mays believes that Ecotect works well for both architects and engineers because it allows architects to connect to the BIM tool and engineers to the more sophisticated analysis tools.

Mays noted that two things that ArchiCAD does are different from the way Green Building Studio and Ecotect work with other BIM products. The major distinction is ArchiCAD’s ability to map objects between the applications, giving a lot of efficiency in managing zones. The zones are used for multiple purposes. “It’s kind of a difficult concept for some architects: that you’re trying to identify the negative space of the building and not the solid portions of the building,” he said. “So this is the same information that you might use for your programming, for your blocking and stacking diagrams, and for other purposes [like] acoustical analysis.” Ecotect also does that, so understanding the volumes within the building and connecting to products and communicating data is a different approach.

The second thing that Mays says is unique to ArchiCAD is referencing between objects within ArchiCAD to the objects within Ecotect. This is important because when the properties of a window or door have been defined once, it has the same name in both applications. They’re mapped together so that when an item is updated in one place, it translates to the other. Mapping is important because sustainable design analysis can be used all the way from conceptual design to schematic design to design development to construction documents, allowing constant evaluation of lifecycle costing.

The tools within Ecotect allow the architect and client to see how energy will be distributed in a building. “You can see how much penetration you’re getting with daylight. It’s very graphical. The flow of air, the effects of light, heat, cold: you can see these very easily in Ecotect,” Mays explained. He noted that both ArchiCAD and Ecotect are very visual, and together they give the client a clear idea of the appearance of the building.

During the first few weeks of design, fundamental decisions are made that have an enormous impact on the energy consumption of the building and therefore the lifecycle cost. Mays said that not only does ArchiCAD work well with Ecotect, but Graphisoft also developed the virtual construction products Constructor, Estimator, and Control, recently spun off to VICO Software. Whereas Ecotect and other energy products tell you how much it will cost to operate the building, Constructor, Estimator, and Control tell you what it will cost to build the building. So now, the design team can evaluate capital and operational costs very early in the process and make a balanced decision between the two.

 BIM in the Future
All three providers expect the level of detail, interoperability, and integration to increase dramatically over the next few years. Bentley’s Roberts said, “As BIM really becomes the standard of practice, which it’s quickly moving towards, I think it will enable the design team to think truly and deeply about sustainability rather than as an added layer onto their design process. If it becomes integral to the design process, rather than something tacked on to the design process, that’s when it really adds significant value.”

Bhatt from Autodesk added, “I think BIM and sustainability connected, and then ultimately sustainable design as a general concept won’t be just a “nice to have” in the future. It will be an absolute “have to have” -- a requirement. You will not be able to separate them in the future.”

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