Why MEP Contractors Change MEP Design Models

In the MEP environment, a building’s MEP designs are initially developed at high level and then detailed to make them clash free and installation ready. MEP designers/consultants play a significant role in design decisions, construction planning, cost estimation and documentation. While design development is typically the role of the consultant and design detailing is done by the MEP contractor, when using MEP (M&E) BIM models and Revit BIM libraries, contractors invariably need to make changes to the MEP design model created by the consultant. 

To make a design installation ready, contractors may have to make several changes to the design-intent such as resizing of ducts, re-routing of pipework, adding wall penetrations, bolt locations and datum points for hangars and changing equipment. Once these changes are made by the contractor, the design would be installation ready and will need to be approved by the MEP consultant. The question that this article seeks to answer is why do MEP contractors need to make these and other changes to MEP design models?

• To adjust invert elevations – During the installation of plumbing or drainage pipes, MEP contractors deal with the point of the bottom inside of the pipe, this is known as the invert elevations. To guide pipe design and match the invert elevation height, elevation information can be vertically adjusted at the centre of the pipe using Revit. However, if you are unaware that the elevation information is in centre of the pipe, it could cause confusion in adjusting invert elevations and create discrepancies while coordinating with other disciplines. This is the reason why MEP contractors need to manually adjust invert levels, create spot elevations for the inside bottom of the pipe and change the design models to install pipes which are coordinated with other disciplines. 
• To retrofit MEP systems into a prefabricated module environment – Planning for prefabrication of MEP components into the 3D model would not be considered by designers and therefore the contractor is the party who will make adjustments to services to allow them to fit into prefabricated modules to maximise the advantages that are gained from off-site fabrication. In several MEP projects which require prefabrication of risers, ceilings and plant room areas, MEP services drawings and modules specifically for fabricators and installers is necessary to facilitate proper installation. MEP contractors make changes in the MEP design model to ensure that services fit within modules within the ceiling or riser space to allow prefabrication of MEP components off-site allowing faster installation on-site.
• To facilitate efficient spatial coordination – When installing MEP systems, effective spatial coordination with other building services and disciplines is imperative. A consultant may leave clashes in a model as his focus will be on getting a design issue by a due date. A contractor is more concerned with actual fitting so after conducting a clash test on the 3d model, MEP contractors will invariably change design models to ensure that all services are not clashing. The installation programme of the MEP system depends on clash free layouts and MEP contractors must make sure that MEP systems are spatially coordinated with other disciplines in the 3D model before creating M&E (MEP) Coordinated Drawings.
• To deal with constructability issues – There are several factors that influence the constructability or sequence in which MEP systems are installed. Some of the conflicts that require a change in MEP design include routing, fitting and sequencing of large equipment within a given space, conflicting piping network and installation of MEP systems within a crowded space. As MEP contractors need to tackle several conflicts and constructability issues before installing MEP systems, a change in MEP design usually occurs. 
• To install MEP systems economically and efficiently – While the MEP design intent may seem to be perfectly coordinated, it need not necessarily be economic or efficient when it involves installation. There are several costs involved when changes need to be made after installation such as re-routing pipes to reduce bends, re-positioning ducts to allow supply and extract in the correct locations, changing equipment or adding wall penetrations, bolt locations and datum points for hangars. To make sure that MEP systems are installed economically and efficiently, MEP contractors must make changes to MEP design models.
• Changes in materials and components – In some cases the MEP model from a consultant is accurately modelled with specified parts, materials and components. However, in some cases projects do not have specified parts and a consultant may use library elements from Revit leaving the contractor to update the model using his planned procurement schedule. This will result in changes due to sizes and access requirements for new components such as a change from copper to plastic pipe which is thicker or a change from one set of pumps to another that may be larger and may have different valve arrangements. The knock-on effect of such component changes can mean that other systems also need to be changed. 

Given the many reasons why MEP contractors need to change MEP designs and with the adoption of MEP (M&E) BIM practices, there is an overlap in the scope of MEP contractors and consultants during the planning phase. To know more about how you can reduce the duplication of efforts, additional costs, manage project schedules and reduce scope overlap, read more in this post to find out the possible routes that can be taken.

To ensure MEP design models are installation ready for MEP contractors to use on site, a viable solution would be to work with a 3D BIM coordination specialist or MEP engineering design service provider. At XS CAD, our experienced team of MEP designers in India provide BIM support and spatially coordinated building services drawings for key stakeholders in the MEP (M&E) industry, from MEP (M&E) consulting engineers and MEP (M&E) building services contractors. In our spatially coordinated MEP building services models, we use the latest 3D MEP (M&E) modelling software (Revit MEP) and clash detection technology (Autodesk Navisworks) to provide 3D M&E (MEP) coordinated drawings which adhere to engineering standards, the structural and architectural elements within a building.

Approaching MEP BIM Projects Using Coordination Specialists

The MEP (M&E) design and contracting industry across the globe faces renewed challenges with the advent of BIM which is increasingly used by AEC firms. Firstly, of all the major stakeholders involved in an AEC project, building systems design and engineering historically formed the last phase of design, however BIM dictates a more synchronised approach by all disciplines, requiring them to work in parallel from the early stages of AEC design. Secondly, the facility owners and investors always demand increased efficiency, waste reduction and on-time/in-budget completion.

As a result, progressive MEP engineering firms are increasingly adopting MEP (M&E) BIM practices to, a) work in parallel with other disciplines; and, b) meet complex project demands from project stakeholders.

Implementing BIM can pose a challenge as its adoption requires significant investment in equipment and training as well as changes to overall workflow and internal processes. With this in mind, many MEP engineering firm’s partner with 3D BIM modelling and building services coordination specialists, such firms possess expertise of parametric modelling and BIM development. As well as immediate expertise offered by such coordination support firms, transitioning to a BIM-based MEP workflow from a conventional CAD-based design workflow requires the type of planning and workflow streamlining that many firms are only just implementing and therefore the skills to handle such projects immediately are not in place.

Once the specialist MEP coordination firms are on board, they face the challenge of handling BIM projects and in particular maintaining a version controlled model. When using BIM for pre-construction planning and construction documentation effective communication and the use of modern collaboration platforms, usually hosted in the cloud, help to maintain a version controlled model. 

The BIM managers representing key project teams: architectural, structural, and MEP (M&E) engineering must collaborate and communicate to ensure the integrity of design data as well as adherence to project deliverables. For his/her part, the MEP (M&E) BIM manager will need to gain an insight into the architectural and structural BIM models prepared by the respective teams and use that data for his own inputs. As well as a detailed review of the current BIM standards of the project, knowing the specific components that will be used and then planning the coordination efficiently to include bracketing, lagging, access and maintenance will be taken into account. This insight can then be used to prepare an MEP central file that serves as a reference point to the downstream MEP design team.

The emerging standard of LOD (level of detail) means that the BIM manager representing the MEP (M&P) team must work to the specified LOD for the project, this will influence the detail within the drawings whether it is at the schematic design (SD), detailed design (DD) and then  construction documentation (CD) phase of the project. This ensures the model does not contain elements that are not required or will not be of any use to the trade subcontractors. Another key decision before the MEP design team starts modeling is how much custom content (parametric families) will need to be created within the BIM application in addition to the information that will need to be developed in a CAD package and linked to the BIM application.

If the above aspects are considered before initiating upon a new BIM-enabled MEP (M&E) design project, the MEP (M&E) BIM manager will serve as a primary link between the in-house design team and the architectural / structural BIM managers (who represent their respective teams). As a result, any update on the architectural or structural models will be communicated to the MEP BIM manager who can then update the MEP central file which in turn acts a point of reference for the downstream MEP design team to model upon. This sets the stage for streamlined and coordinated MEP designs using smart parametric models.

 

For more information about our dedicated MEP (M&E) BIM modelling support and coordination service for MEP (M&P) designers, consultants and contractors contact us.