DALLAS - Building Information Modeling, or BIM, is a quickly developing trend in building design, and it goes deep into building mechanical systems in a way that contractors are finding to be very beneficial to them.

What’s BIM? It’s the digital creation of a building that includes all systems, from the envelope all the way in, based on information provided by the design team (architects, surveyors, consulting engineers, and others) contractor, and subcontractors, straight to the owner.

Each member of the team can add their own specific information, and all members can track changes to a single model. Among its benefits, BIM provides conflict detection. The program informs team members about building systems or components in conflict. In essence, the building is “built” digitally - and when errors are caught at this preconstruction stage, they are so much easier, and cheaper, to correct.

CONFLICT PREVENTION

Jeff Hartnett, commercial product manager for Lennox Industries, called BIM “a tool or design approach for architects and engineers to develop and design a building structure.” His biggest perceived difference between BIM and previous types of design tools, is that “first, they do the modeling in three dimensions, so they can see how different aspects of the building design overlap or potentially have conflict with each other.”

It also is intelligent, he pointed out, in a way that goes beyond previous types of intelligent design. “Many aspects of the BIM drawing tie back into different dynamic aspects,” Hartnett said. Among other things, it simulates how various systems and structural pieces would interact - before the groundbreaking date is even set.

“One of the biggest advantages is that BIM can prevent field corrections,” he said. “With the simulation of how everything will work together, they will find many of the interferences rather than finding them at the jobsite. Bottom line is, it saves designers and owners money in the actual build process, with fewer changes.”

This naturally means a streamlined job for the mechanical contractor, with fewer change orders - which means a more profitable job with a greater chance of on-time completion.

By having the models, Hartnett said HVAC contractors can determine, for example, “what is the correct electrical wiring to run, and what size piping they need for gas.” It can also help them design ducting and determine airflow, to make sure they have the correct airflow. “A lot of it can be done automatically” through the BIM program, he said. A mechanical contractor can simulate a suggested duct setup; “the program will find the interference and make corrections.”

From an OEM’s perspective, he said, “there’s less opportunity for errors. Using BIM objects for our equipment means one less set of hands is transferring the information. Our information is dropped into their building design; there is no interpretation” by designers or others on the team. In the past, he said, “they would have to look at our documentation but there’s nothing behind the 2-D drawings; they would have to determine what all it had: inputs, gas, etc. They would have to get that from our documentation.”

Using BIM, the entire building team, from designers to installers, are “essentially getting a lot more information than they had in the past,” Hartnett said. “Objects are loaded with our base information; it comes loaded with a lot more information than it would have had without the BIM object.”

At this stage, it’s hard to know how many commercial projects are using BIM. “Several of our large customers have asked for it,” said Hartnett. “It’s kind of at the early adopter stage, but it’s definitely growing in interest.”

DEPTH

How deep does the information go? From an HVAC perspective, Hartnett said it provides dimensions, weights, electrical loads, gas loads, all connection points, and performance. Information such as hookups and sizes of the unit are especially helpful for contractors, he added. “Say you’ve put in three rooftop units, therefore you need to run a 1.5-inch gas line; it will reference those parameters in the object,” he said.

“That’s where the intelligence part comes in. It sees that it’s got a certain electrical load, gas requirement, and airflow, and you can use it to tie into the utilities, duct system, and so forth.”

Contractors are actually the ones pushing for BIM, he said, “because it allows them to be more effective, with fewer field change orders,” and it allows them to be more profitable. In short, they can get the work done faster and with a greater capability of being on time.

“It’s actually being pushed from the contractor level, because the contractor has more to gain,” he said. Change orders are an unwelcome and unanticipated expense in time. Forcing a field solution can be an undesirable situation, and it might result in something that’s not part of the original design intent.

“A contractor can bid a job that’s done in BIM with a lot more confidence,” he said, “when they know there will be fewer issues.” It also means they might feel less of a necessity to add a safety factor to their bid, to cover potential unexpected issues. “You would expect their safety bid would be a lot lower percentage.”

With the growing contractor interest, involvement in BIM has been “more of a pull than a push, and we want to keep up with it,” Hartnett said. “From the commercial side, rooftops are our biggest focus.”

In fact, members of the design team can now integrate the manufacturer’s new Energence™ and Landmark™ rooftop units using BIM objects downloaded from the manufacturer’s Website. The 3D Revit™ models include complete product parameters and unit performance information on 3- to 50-ton Energence rooftop units and 2- to 25-ton Landmark rooftop units. The Revit families also provide cooling and heating capacities, electrical loads, and the size and location of electrical, gas, duct, and condensate connections.

BIM software helps a project’s design and construction teams communicate more clearly and easily, providing consistent and reliable information for all aspects of the project. Using BIM objects can allow these teams to save significant design time while improving the accuracy of their HVAC system designs.

For more information, visit www.lennoxcommercial.com or call 800-953-6669.

Publication date: 03/22/2010