MEP families in Revit
connectors and BIM pipes
Modelling a project’s building services — HVAC, plumbing, electrical — is usually more complex than modelling the usual architectural elements. That is why Revit offers a different type of family, with its own system connectors, which should be understood before accepting any building services model as sound.
Keep reading: what distinguishes an MEP family ↓
Why building services need families of their own
A door or a wall is resolved with relative ease in BIM. An HVAC or plumbing network is not.
BIM modelling of a project’s building services is usually more complex than modelling the most common architectural elements — doors, windows, walls. A diffuser, a pipe or an electrical panel is not just a geometric shape: it is part of a network that has to behave as one, with flow rates, diameters and connections consistent with each other throughout the whole system.
For this reason, Revit allows you to work with MEP families, a type of family designed specifically to handle that complexity. They do not replace the modeller’s judgement, but they make the work much easier: they provide the structure needed for each element to know which system it belongs to and how it relates to the rest.
System connectors: the heart of the MEP family
It is the element that separates an MEP family from a generic architectural family.
Among the main elements that differentiate BIM families from MEP families are the system connectors — also called MEP connectors. They give the family the properties it needs to interact with the rest of the network within the project environment.
A common example: when modelling an HVAC installation and defining a swirl diffuser, working with MEP families makes it possible to set several connectors, such as the air duct connector. Once the diffuser is placed in the project, a duct can be run directly from that point, inheriting the properties of that particular HVAC installation.
This is what makes it possible to link all the elements of a single network and organise their properties better: the connector is not a decorative detail, it is what makes the model understand that this diffuser belongs to an HVAC system and is not an isolated object shaped like a diffuser.
A system connector is what turns an object shaped like a diffuser, a pipe or an electrical panel into a real element of a network, able to inherit and pass on its properties.
Pipe families: why generic ones are not enough
Autodesk Revit includes generic pipes as standard. For an engineering project, they are almost never sufficient.
By default, Autodesk Revit offers rather poor generic pipes, which are not usually suitable for engineering projects. In this type of project you need to know the real dimensions, the type of pipe, the standard it follows and the material it is made of — and Revit does not provide that information as standard.
What it does allow is the creation of your own pipe families, then organised in BIM libraries. Those libraries are the key to managing building services information: once the real characteristics of each pipe have been defined, they can be reused in any later project without entering their data from scratch.
At A3D we have spent years building families for engineering projects, to the point that we now have more than 90% of the most widely used pipe families on the market already resolved in BIM format (A3D’s own figure). It is a base that greatly eases the modelling of the building services of any project that comes our way.
Organise MEP families in a BIM library
The main difficulty in creating MEP families is having to start from scratch on every project.
Entering the data for each element, resolving the joints between pipes, organising the information for each system: if that task is repeated project after project without a library in between, the cost multiplies unnecessarily. That is why it is worth having a complete library of MEP families before starting any BIM project, organised by discipline — HVAC, plumbing, electrical, fire protection — and not as an unsorted folder of loose files.
Working with a library that is already resolved gives immediate access to that kind of resource, which avoids the usual difficulties of any team with little BIM experience when modelling a project’s building services: families with incomplete data, pipes with no associated standard, or poorly resolved connectors that break the network at the first change.
The rest of the series on BIM families
This is the second of four pages on how BIM families are designed, managed and applied in a real project.
Frequently asked questions
Complete answers to the most common searches about MEP families in Revit.
What are MEP families in Revit?
MEP families are the objects used to model mechanical, electrical and plumbing systems — HVAC, drainage, electrical, fire protection — within a BIM project. Unlike a generic architectural family, they incorporate system connectors that allow them to link to one another and pass on properties such as flow rate, diameter or fluid type throughout the whole network.
What is a system connector in an MEP family?
A system connector is the point of an MEP family that enables it to interact with the rest of the network: an air duct, a plumbing pipe or an electrical cable. When an HVAC diffuser is defined with its duct connector, for example, Revit allows a duct to be run directly from that point and inherit its properties, instead of leaving the element isolated from the system it belongs to.
Why are Revit’s generic pipes not suitable for engineering projects?
Because an engineering project needs to know the real diameter, the material, the standard it follows and the technical specifications of each pipe, and the generic pipe families that Revit includes by default do not contain that information. To solve this, you need to work with your own pipe families, built with real manufacturer data and organised in a BIM library.
What is a BIM library of MEP families?
It is the repository where MEP families that are already resolved — pipes, ducts, equipment, luminaires — are organised so that they can be reused in different projects without defining their data from scratch again. The more complete and well maintained the library, the less time is lost at the start of each new project and the lower the risk of working with invented or incomplete information.
Which MEP disciplines are modelled with BIM families?
The most common MEP disciplines in a BIM project are HVAC, plumbing and drainage, electrical and lighting, and fire protection. Each has its own types of connectors and its own families — diffusers, pipes, cable trays, sprinklers — and all of them coexist in the same model, coordinated with one another to detect clashes before construction.
We do this work every day
Resolving an MEP family properly — consistent connectors, real manufacturer data, pipes with their associated standard — is exactly what we do at A3D every day, with a library of our own built over years of engineering projects. If your team needs to strengthen its MEP library or needs specific Revit MEP training, we go through it together on your project.
And your MEP families: what state are they in?
Tell us about your plant: an A3D specialist tells you in 15 minutes where to start, which area to survey first and with what scope.
Prefer to continue with the series? Read about complex or assembled families or go back to the system connectors covered on this page.