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Mechanical, Electrical and Plumbing (MEP) Modeling at 210 King - Version 1
October 4, 2010

MEP Model
Figure 1: HVAC model at 210 King St. East.

Since our last blog post describing the 210 King Revit model we have made significant progress in incorporating mechanical, electrical, and plumping (MEP) information into our BIM model. The integration of MEP information with our existing architectural model introduced an additional level of complexity in managing the massive amount information found in a typical MEP scheme. Compared to the long tradition of 3D architectural visualization, production of MEP drawings in a 3D environment is rather new to the AEC industry. Typically MEP drawings are drawn in 2D and then passed on to the architect who will be responsible for coordination among all the consultants. A large aspect of this coordination involves checking for clashes among architectural, structural, and MEP components. This is a particularly challenging task when dealing with large projects. Given the ability of BIM to incorporate information pertaining to all disciplines in a singular 3D environment, we can expect a better workflow and clearer communication among all the disciplines describing a building. Figure 2 illustrates a few screenshots where our 210 King BIM model was directly exported from Revit to Autodesk Navisworks for inspection. Using this method we were able to quickly identify errors and verify the accuracy of our MEP model.

Navisworks Screenshot
Architectural and MEP clash
Figure 2: (Top to bottom). Models from Revit Architecture and MEP are combined in Navisworks for quick inspection and annotation. A tagged-view marking a clash between a duct and building envelope.

As mentioned above, MEP modeling has a very short history and existing workflows utilize only a small part of BIMs' capacity in visualizing, analyzing, and simulating a building. Furthermore, lack of appropriate guidelines in BIM for existing buildings presents a challenge in defining an appropriate level of detail (LOD) when dealing with complex MEP systems.

Our HVAC model is mainly comprised of:

  • Ducts
  • VAV Units
  • Zoning Scope
  • Air Terminals
  • Roof Top Units

The combination of these components together defines a system that can be described on a topological level. The topological description essentially refers to physical configuration and connections among the components. For instance, our building consists of five HVAC zones supplied through five Roof Top Units (RTU). By selecting a RTU we can follow an entire branch of connected ducts for a selected zone (Figure 3).

HVAC Connectivity 01
HVAC Connectivity 02
HVAC Connectivity 03
HVAC Connectivity 04
Figure 3: Looking at connected ducts supplying fed through a selected RTU.

In our first attempt to model the HVAC system we had to rely on old drawings we retrieved from MEP consultant involved in the 1997 renovation. However, we quickly noticed discrepancies between the drawings and actual layout of mechanical units on our rooftop. Since the time of renovation some equipment, such as a chiller and many A/C units (dedicated to server rooms), have been added to the roof. Figure 4 illustrates an on-site sketch of our current roof top configuration. This diagram is a simplified version that does not include the gas line and our boiler room, but it is being used for a quickly laying out the existing pieces at their approximate location on the roof.

Additionally, finding an appropriate BIM object for all our existing mechanical equipment has been rather challenging. BIM objects are digital models of both the physical and mechanical characteristics for mechanical equipment. For the time being, we have incorporated simpler representation of BIM objects into our Revit model. However, we have been documenting the existing equipments and we hope to work with existing manufacturers to produce higher quality BIM objects. It is worth to note that we can refine the level of detail on our model over time. Therefore, we can replace our existing BIM objects with BIM objects provided by manufacturer of MEP equipment.

In our next blog we will provide some additional details about our MEP model and some of the keys points we have learned during our modeling process.

Architectural and MEP clash
Figure 4: On-site documentation of mechanical layout on the roof.

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