Posted on April 25, 2020 by Jonas Claros Vasquez and Bruno-Pierre Caron
Category: Technical

Our tips and tricks for MEP modeling in Revit

If you’re part of an MEP (Mechanical, Electrical, Plumbing) project - whether your role is to produce, manipulate or even analyze the model - it is essential to be aware of certain issues you might encounter in Revit. We want to offer some quality checks you can do to keep your model "healthy" and running at full speed. 

Without these checks, you could face problems that are not always easy to spot, such as:

  • Schedule quantities indicating false or incomplete data
  • Disturbed coordination workflow due to elements which are not properly oriented 
  • Inaccurate representation of precisely modeled elements
  • And many more...

Here are some tips and tricks so that you can more easily spot problems in your projects and, ultimately, be more productive in your work!

The toolkit you need

To display and understand the model data, there are several tools at your disposal:

  • Create quantities, or schedules which allow the extraction of data from the model
  • Label elements of the model and display its associated data 

Although these features are very powerful, one question keeps coming up:

« Is the data illustrated correct? ».

From a software point of view, the data displayed reflects the reality of the values extracted from the targeted elements. This means that the data displayed is exact. However, this does not guarantee the validity of the positioning of the elements, or the parameter values themselves. Consequently, the extracted data can be inaccurate because it depends on the quality of your modeling and the information associated with it.

The expression «Garbage IN = Garbage OUT» takes on its full meaning in a digital model. 

Are the elements at the right level?

There are several methods for modeling main pipes or ducts which cross several floors (commonly called “main” in the field). One of the most common methods is to use elevation views. In this case, the elements will not have the correct reference level, because Revit uses the element's starting reference level, which is the level of the first element in the drawn sequence. So even if they cross several floors, all these elements will be classified by the level of the starting element. This will distort the data extracted from the labels:

Démonstration du niveau de référence et du décalage de l’élément lors de la modélisation d’une gaine de ventilation dans une vue de coupe ou d’élévation
Figure 1.0 - The reference level and the element are offset when modeling a ventilation duct in a section or elevation view.

When modeling in Revit, it’s easy to miss what is happening in the Properties bar, especially when we use the famous "Copy / Paste" function. 

False data extracted from a ventilation duct associated with the wrong reference level
Figure 1.1 - "False" data extracted from a ventilation duct associated with the wrong reference level.

Most of the time these small details slip under the radar, but they can actually have a major impact on the project and its coordination.

In a section/elevation view, Revit uses the level of the first element drawn as the reference point, whereas when you are modeling in a plan view, it uses the level of the view to model correctly from the start.

However, if you want to assess the extent of the adjustments to be made in a model, you can quickly visualize color-coded reference levels of the plumbing pipes and/or ventilation ducts thanks to the "Color Splasher" tool which is available through our add-ins manager.

Using the
Figure 1.2 - Using the "Color Splasher" tool to color-code data relating to the reference levels of the ventilation ducts in the digital model.

Doing this "clean-up" can be complex and tedious, so we have developed a script that will allow you, in just a few clicks, to modify all the values of the reference levels and offsets associated with the elements of your model. The dynamo script is available via our add-ins manager and its detailed description in our blog post.

Modeling the right way!

As far-fetched as it may seem, it’s actually quite common to see elements that seem well modeled in a plan view, but in reality are not if you look at them in a section view.

There are different ways to model elements hosted on ceilings. Let’s look at their respective benefits and drawbacks in order to choose the one that will best apply to your needs.

Here are two separate methods that we see being commonly used:

  1. Sprinklers, diffusers, exhaust grilles, light fixtures, etc. are hosted directly on the ceilings from the architectural model. On the plus side, this method facilitates an effective coordination workflow because as soon as the ceiling of the architect's model changes elevation, all elements hosted on this ceiling automatically follow. On the other hand, this method can create unwelcome surprises when items have been moved or even sometimes deleted without our consent.
  2. Sprinklers, diffusers, exhaust grilles, light fixtures, etc. are hosted on reference planes. This method allows you to control the elevation of elements independently of the architectural model, and prevents unwanted surprises of elements being moved when they were already coordinated. In addition, if the architects decide to remove their ceilings, this avoids pesky "disconnection warnings" as the elements are disconnected from the host.

We recommend using reference planes to maintain full control over the position of your elements in your model. Furthermore, you can easily move several elements at the same time by changing the elevation of your reference planes, thus speeding up coordination with the latest architectural changes.

That said, have you ever noticed that elements sometimes get reversed when placed on a reference plane? Well, the direction of creation of the reference plane actually determines the orientation of the hosted elements. Yes, it’s true - reference planes also have a direction!

Creating a Left to Right reference plane
Figure 2.0 - Creating a "Left to Right" reference plane.
Creating a Right to Left reference plane
Figure 2.1 - Creating a "Right to Left" reference plane.

Please note that this problem does not apply to all categories of families.

A quick way to identify the orientation of your reference plane is:

  • If the name is located below the reference plane = Created from left to right
  • If the name is located above the reference plane = Created from right to left

A good practice to put in place is to always make sure to model in the same direction, whether you are modeling reference planes, conduits, pipes or ventilation ducts. This will certainly save you some headaches!

To detect this type of problem as soon as possible, we also advise you to always work with a plan view, an elevation view, and a 3D view in order to have a three-dimensional visual of what you are modeling.

So, how do you correct this problem if you already created reference planes in different directions? It sounds like a simple fix: you just need to reverse the item. However, Revit does not offer the possibility of performing this action on several elements at once. You will have to change the items individually, and unfortunately even this will not solve the problem, because all the new hosted elements will suffer the same fate.

To help you fix this easily and efficiently, we have developed a Dynamo script that will allow you to quickly put family instances back in the right orientation. The script is available via our add-ins manager.


Warning !

If the family's insertion point is not centered in the family itself, it will be moved when the orientation is changed. This is why it’s important to have a well-built library of families!

Annotation symbols!

A common problem our clients often face, particularly in electrical models, is symbols conflicting with each other! For example, let’s say you have a magnetic card reader, a switch, and a power outlet, all aligned one above the other in elevation. In a plan view, the symbols will be superimposed on top of each other. This problem is not always easy to detect, especially when it is the same symbol clashing.

The solution is to host the symbol on a mobile reference plane, which is itself based on two other reference planes including the “Center left / right” plane, and constrained by two parameters of dimensions and two formulas (Figure 3.0). This makes it possible to enter a positive or negative offset of the plan symbol while keeping the position of the element in 3D.

Here is an example demonstrating a possible solution to fix this problem:

Repr3 sockets viewed in plan versus elevation view
Figure 3.0 - 3 sockets viewed in plan versus elevation view.
Parametric configuration of the annotation symbol with 3 reference planes: the original “Center (left / right)” plane, a “Left” plane referenced on the “Center” plane and a “Right” plane referenced on the “ Left. Using the formulas, either Center and Right, or Right and Left will be superimposed, allowing the symbol to move to one side or the other of the element.
Figure 3.1 - Parametric configuration of the annotation symbol with 3 reference planes: the original “Center (left / right)” plane, a “Left” plane referenced on the “Center” plane and a “Right” plane referenced on the “ Left". Using the formulas, either "Center" and "Right", or "Right" and "Left" will be superimposed, allowing the symbol to move to one side or the other of the element.
Positive offset of an annotation symbol
Figure 3.2 - Positive offset of an annotation symbol.
Negative offset of the annotation symbol
Figure 3.3 - Negative offset of the annotation symbol.

Thanks to this method, you will be able to move your annotation symbols without affecting the geometry associated with the element, allowing an accurate graphical representation of the number of elements modeled.

NB: Do not forget to notify the specialized contractor of the layout of the installation required, with additional notes or details with additional views to ensure a good understanding of the work to be performed on-site.

In conclusion!

Rigor and attention to detail are vital when working with Revit. With these few examples, we hope that you will be able to spot and correct errors more easily on your projects.

Of course, this is just the tip of the iceberg. There are many more modeling issues that you can encounter, and many possible solutions. For more customized advice, please do not hesitate to contact us in order to benefit from our expertise.

Remember that the quality and reliability of the information contained in your models are the keys to better collaboration and better coordination between project stakeholders.

Jonas Claros Vasquez
BIM Specialist, BIM One

Bruno-Pierre Caron
BIM Specialist, BIM One

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