Revit MEP Scheduling for Design

February 6th, 2013

There comes a time when users of Autodesk® Revit® MEP move beyond merely 3D drafting a project and start leveraging the Revit database to increase confidence in the design and increase design efficiency. There are a lot of entry points to penetrating the Revit database. Leveraging Revit’s scheduling function makes a lot of sense for this task because it should already be a familiar tool and it has the ability to directly query the database. While it is not the most intuitive tool, most everything in the database can be directly scheduled. This article will focus on tips and tools for mining that data to help validate design information and increase design accuracy.

Scheduling in Revit MEP requires MEP families in the model. These families need to contain required data for design. This is typically in the form of parameters inside the family. It takes considerable thought to get just the right data in the right place when it comes to making the process of design work for individual firms, but some things are right in the base product. The data is a common thread through the design. Crafty BIM managers will have to thread quite a few needles to optimize the perfect Revit setup.

There are some basics tips to consider before diving too deep into the pool.

  • The number of decimal places influences calculations, so round accordingly.
  • When Space schedules are used, ensure that the upper limit of spaces in the model are set to the level above or higher to ensure the entire volume of the space is considered.
  • In certain situations, use the calculation Point tool new in 2013 to add diffusers and lights to a room or space that even when they don’t intersect the space.
  • Be careful of phasing in projects, rooms, and spaces among other things that are phase-aware.

The rest of this article assumes a basic understanding of Revit schedules. If you need a primer, check out Carla Edwards’ article “Flexible Scheduling” in the August 2012 edition of AUGIWorld.

There are tons of parameters in the out-of-the-box version of Revit. All are valuable and can be used right away. These can be added to any schedule or simply used to report data to the engineer. A good practice is to actually segregate design schedules from construction document schedules in the Project Browser. This can be done by adding a subcategory to the design schedules and sorting the Project Browser by subcategory.

The real power is in creating new parameters to perform some of the mundane tasks that engineers constantly face. Here are some situations followed by some parameters and formulas.

HVAC Calculations

Many HVAC calculations require engineers to find the area in a space per person. Like most of the formulas to follow, this one is only really functional inside a space schedule. First use the roundup function in Revit to round the number of people to a whole number.  In this example, the new parameter is called CalcPeople.

Actual Number of People CalcPeople = Roundup (Number of People)

Then divide the Area of the space by the actual number of people:

Area per Person   AreaPerPerson = Area / CalcPeople

Outside air calculations require some pretty simple math:

Basic Corridor Calculation (0.06*Area)

We can use the area per person parameter to help find the basic office load:

Basic Office Load Calculation (AreaPerPerson * 5sf) + (0.06 * Area)

The LEED EQc2 naturally follows from that:

LEED EQc2 Calculation  (Office OA * 1.3)

If/Then statements can be used to add another layer of automation to calculations. In the example below, the room occupancy is checked to see whether or not it is an office space. If it is an office space, the actual number of people in the office are added to the calculation; otherwise the actual number of people is skipped.

IF(Room:Occupancy=”Office”,( (CalcPeople * 5sf) + (0.06 * Area)), (0.06 * Area) )

Labs, medical spaces, and other room types are required to be positively pressured. The formula below can determine if the design pressure for the room is positive.

Room Pressure = Actual Supply Airflow-Actual Return Airflow-Actual Exhaust Airflow

Conditional formatting can be used to display rooms with negative pressure in RED. Under the Formatting tab, select the Conditional Format button and have it alert the user to a condition less than or equal to zero room pressure.

Location, Location, Location

Some Revit family categories are aware of their location in the model. See the table below for some of them and what they can report.

To find out how many of these objects are on any given level, create a multi-category schedule and sort it by level.

Ceiling height seems like a pretty simple thing to get, but it is not so direct in schedules, or is it? Take a couple of things you do know—such as volume and area—and divide them. What’s left? Ceiling height, and for some unknown reason the math works out and gives you a ceiling height in feet and inches. There are plenty of reasons to want the ceiling height of a space, and this little formula allows you to put it in any space schedule.

Ceiling Height = Volume/Area

A similar formula can be used to calculate the window area in a space. Once a space is determined, the windows in that area can yield their area by multiplying window height by window width. Weird, but true—the space has to know the windows are there and has trouble recognizing the windows that are accurately placed. To help Revit find the windows, reverse them so the panes are in the inside of the space instead of the outside.

Window Area= Height/Width

Inside the Inside

Nothing gets as awkward or as complicated as embedding a schedule in a schedule. In the example below, a window schedule is embedded into a space schedule. The ceiling height is added for good measure.



Embedding space-aware objects into a space schedule can be used to document light fixtures, electrical devices, mechanical equipment, and air terminals by space, reaping such wonderful data as  footcandles, watts, and cfm per room or space. Think about how often this is estimated or required and the valuable time of the engineer used to acquire it. If a user can be just as sure of the information without doing a hand calculation, then it should be obvious that the saved time will either be profit or well utilized, creating a better product.

These are just a few examples of the types of information a schedule can provide. It is straightforward to think of the normal schedules on a sheet. This information is the stuff that designers and engineers can use as they design, providing direction and validation early in the process, updating, and design progresses. Scheduling for design considers a firm’s processes and the required information of engineering, and then applies a little out-of-the-box thinking to streamline design.

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