Not too hot to handle

BIM is starting to streamline the energy-modelling process and reduce its costs

In many modern industrialized countries, when all types of buildings are included, they account for 35-40 per cent of the total energy consumption pie-even more than transportation. As concerns around energy efficiency, costs and one's carbon footprint continue to grow, so too is the importance of building design principles and methods that address these issues.

Energy modelling is widely regarded as a critical tool for optimizing building design and performance when it comes to boosting operational efficiency and cutting fuel requirements. An energy model is a representation of a building for the purposes of an energy simulation, which, in effect, takes a design through a series of what ifs and scenarios related to the building's possible energy use and profile. Ideally, it factors in all the design and operating parameters associated with energy consumption.

Although energy modelling to augment efficiencies has been applied to projects on an occasional basis for many years, it has often been seen as a cumbersome and costly process. Energy modelling was typically done at a late stage of design, once detailed information on design and building components was available to the energy specialist.

WHAT'S THE POINT?

The result, all too often, though, was that relevant building features could not be altered, even if the energy analysis indicated that they should be, according to a paper by experts at the Engineer and Research Development Center (ERDC) of the U.S. Army Corps of Engineers. So one might wonder what was the point of an exercise to uncover a best decision that was impractical to implement.

But today, the energy-modelling side of the design-build equation is undergoing rapid change for the better.

A key to consistent and successful energy modelling-and effectively implementing its conclusions on a project-is to include energy modelling analysis at the early stages of design. It makes selection and implementation of the best options easier, say the authors of the ERDC paper.

Recent innovations in software-supported Building Information Modelling (BIM) systems and energy modelling software are now enabling designers to assess energy strategies and systems in the earliest phases of design.

"New and emerging tools allow a user to submit data from project BIMs to test energy-saving ideas and see results quickly. This will help teams make energy-conscious decisions early in design, when those decisions have greatest impact on the building's life cycle," the authors of the ERDC paper write. They note that such BIM tools are also applicable to retrofits.

Thanks to today's BIM technologies, recreating the building model for energy analysis, and using simulation tools to ask "what-if" questions and develop scenarios, are ceasing to be costly, labour-intensive processes for making energy-related decisions.

BIM software (Autodesk Revit Architecture is perhaps the most widely used) has been touted for its compatibility with energy-modelling software, but there are challenges, says James Furlong, a principal with Stantec Inc.

"You have to clean up Revit drawings for energy modelling in IES Virtual Environment [an energy modelling software suite]," he says. "If, say, a wall is not very well-defined in Revit because it is a preliminary design, IES might crash or misinterpret the data."

A recent instance of misinterpretation occurred, he says, when the IES energy-modelling software mistook what was in fact a design for an atrium for a mini-tower.

But glitches of this sort can often be avoided, says Furlong, who also emphasizes that energy modelling is most effective when used early in the design process. The key right now, he says, in the absence of software solutions for some of the data-flow challenges, is good communication between the Revit user and the energy analyst doing the modelling.

Cross training can also help, he says, as designers and drafters can learn what types of data they need to give the energy analyst. Plug-in tools exist, but they have limitations. "They're not always the best for fine detail, but they're OK for high-level or broad issues like how should we orient a building," Furlong says.

Better communication at the software-development level could also assist in streamlining data flows between software programs, in the view of one energy-modelling specialist.

DISCONNECTED

Says Ali Syed, the senior energy management project advisor at Hemisphere Engineering Inc.: "There's a big disconnect between BIM and energy-modelling software. Software used in Canada is pegged to Canadian [building] codes, but BIM software developers need to talk to energy-modelling software developers."

Besides plug-ins, there are some data transfer protocols like gbXML, which is another tool for moving data between different networks and software programs. But they too have their limitations. Many energy-modelling software programs cannot fully read gbXML and, Syed says, "Some of the top energy-modelling software cannot read gbXML at all."

These, clearly, are drawbacks, but Syed expects the issues will be resolved within a few years. Software vendors and standards organizations like the International Alliance for Interoperability and the National Building Information Modelling Standard are working to accomplish this.

As Syed points out, one of the big advantages of BIM for energy modelling and other applications is its one-stop-shop aspect.

Energy modellers and others can all work from the BIM-supported design on a whole range of simulations and analyses. Without BIM, each consultant or contractor would mostly work from different sets of drawings and manually input the data, instead of importing it electronically.

When the BIM and energy-modelling systems work well together, "[They] enable very quick decisions," Furlong says.

"Clients are expecting an energy-model result in as little as three days. One person, using Revit, creates one design model that can be used for multiple simulations for sizing HVAC [heating, ventilation, and air conditioning], predicting energy consumption, daylight access, airflow and ventilation, and computational fluid dynamics, for example, predicting precisely where, how and at what temperature air will flow. It saves [designers] from having to do multiple models-one for each simulation."



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