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MP7120Creating BIM Models for Energy AnalysisAryn Bergman, PE, LEED APEnergy Analyst – TL Circle; BIM Manager - Facebook

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Class Summary

This class will present example projects to demonstrate appropriate techniques for creating Revit models and families for energy analysis purposes:1. Autodesk San Rafael HQ 111 McInnis Building – Revit model for the creating of

DOE2 energy models2. Rebuild Sudan’s South Sudanese Primary School project – BIM geometry for

daylighting and CFD analysis in Autodesk® Ecotect® Analysis and Simulation CFD 360 2013

3. Revit Families of Servers for Facebook’s Data Center Designs – Revit families tha are being created to represent Facebook’s servers and connect their models to a databases and spreadsheets through DB Link and the Revit API

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Learning Objectives

At the end of this class, you will be able to: Setup project template files to expedite analysis processes

Create BIM geometry for us in energy, daylighting and CFD models

Create Revit families that can connect to databases and spreadsheets through Revit’s DB Link and API.

Link a BIM model to databases and spreadsheets

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Autodesk University 2012 Power Track

Energy Optimization for Retrofits MP3397-P - Taking Advantage of BIM for CFD Modeling MP3565-P - Using a Retro-BIM Workflow: Case Studies in Energy-Driven

Retrofit Projects MP3765-P - Using BIM to Streamline Your Energy Modeling Workflows MP3784-P - Calibrating an Existing Building Energy Model

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Creating a Project Template File

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Revit Families – Walls, Floors, and Roofs Create exterior an interior walls with a

standard thickness (i.e. 6”) to facilitate alignment

Specify the Function Each envelope property should have

a distinct material and color for identification purposes

Do the same for exterior floors, interior floors and roofs

Each material should have a distinct and identifiable name

Add a descriptive text to the Type Comments field for filter views

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Metal Roofs, Ceilings, and Shading Devices

Use a ceiling family with no thickness for metal roofs if you use the model to create a CFD model

Create a family type for the walls for the vertical shading device and a family type for roofs for horizontal and angled shading devices (thickness doesn’t matter)

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Windows, Skylights, Doors, and Openings

For windows and skylights, create families that are only openings with an extrusion representing the glazing area. Other types may cause errors in energy models and will slow down CFD model run times

Use reference planes to control the dimensions of the opening

Doors are unnecessary in energy models (not required if < 10% of overall surface area of the building per ASHRAE 90.1)

Use Windows for other openings.

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Views Create floor plans and 3D views under the

Discipline “Architectural” so architectural elements are clearly visible and easier to select

For larger projects, create a sub-Discipline “Energy Modeling” to group views with the energy analysis geometry in the project tree

Create a view on the ground floor with Orientation set to “True North” to create the geometry in plan view, but have the ability to rotate the project to true North at any time without affecting other views

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Views

Create additional views for the space and HVAC zones Edit the color schemes appropriately

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Schedule Properties

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Create 3D Views

Create a 3D view for each building component type

The views will hide the other building components so you can export them out as a group

Allows you to manipulate the properties of each component for the entire building at the same time

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Filters

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Creating BIM Geometry for Energy Analysis

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BIM for Energy ModelsGeneral Rules

Don’t use rectangular straight wall openings. They’re not space bounding. Don’t allow any gaps between architectural elements. Space object may “leak” and

prevent the analysis from running. Don’t use in-place families. Use native tools for envelope components. In-place

families don’t translate to the energy analysis program. Don’t include shaft or stairwell openings. Don’t use design options. If you need to show design options, save them as separate

models. Don’t include columns, utility shafts or other components that don’t bind occupiable

spaces. Don’t include doors unless they cover more than 10% of the exterior surface area. Don’t use space or room separation lines. They’re difficult to align in floor by floor

and usually lead to geometry errors.

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Energy Model Settings

Before any export is done, certain settings must be checked: Volumes and Areas must be turned on Edit the Energy settings (Analyze>>Energy Analysis>>Energy Settings)

Set Ground Plane. Set Project Phase. Spaces must be placed in the same phase as the Project Information

phase. Energy Export Complexity set to Simple with Shading Surfaces. The limit of shading

surfaces in the model is 1024. Set Sliver Space Tolerance. Leave the default value of 1’ 0”.

Note: Thermal performance characteristics of elements in the Revit physical model aren’t carried through to the energy analysis programs

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OrientationLinking Models

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Walls Exterior walls should start at the

ground level and extend to the roof, or another upper bounding element

Use constant thickness, different thicknesses will give you errors in your model

Model spandrel glazing as an exterior wall

Use interior walls to define HVAC zones on a floor by floor basis

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More on Walls and Shading Devices Don’t use interior walls as exterior

walls, they won’t show up in your energy modeling program

Model underground walls separately and make sure neither the underground wall nor the exterior wall crosses the ground plane

Model curved walls as a series of straight walls and windows

Model shading devices as rectangles; use exterior walls to represent vertical shading devices and roofs for horizontal and angled shading devices

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Roofs

Roofs should all be the same thickness as floors

Offset roofs properly to that a single space could encompass the entire roof and floor slab properly

Roof should be offset by its thickness

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Floors

Floors should all be one thickness Floor boundaries should either be the

center line, or the interior surface of the exterior walls

Floors should be at the same elevation as the space

Any floor extending beyond an exterior wall should be modeled in two separate pieces; a floor inside the wall and a roof outside

Model slab on grades as exterior floors

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Windows and Skylights

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Ceilings

Only use ceilings when the HVAC system type utilizes the stratification effect (i.e. UFAD or displacement ventilation)

Add ceiling above the occupied volume (usually ~7’) Set the space below the ceiling as occupied and above as plenum

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Spaces

Add one space, set the space number format and provide a common space type name (i.e. “office”).

Set the height of the space to the level above if there are interior spaces on the above floor

If the upper boundary is a roof, the top surface of the space must be offset by the thickness of the roof to avoid adding unnecessary shading devices to the model

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Spaces

For UFAD or displacement ventilation, the top surface must align to the ceiling Add a tag, select it and the space, and use Revit Copy (not Ctrl+C) Revit will use the same space name and will try to guess the next space

number/letter; numbers/letters will increase Edit space types accordingly (i.e. non “office” spaces) Use the Paste Aligned feature to copy similar space layouts from one floor to

another

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Spaces

Under space properties, Select whether the space is occupiable

Select the Conditioning Type Edit Occupancy (People) Edit Electrical Loads

Alternatively, you can use the grouped space schedule to control the parameters for a particular space type

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Zones

Must add an HVAC zone for each space Use the same numerical value as space number Recommended to add an abbreviation for the space type in the zone

name

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Zone Properties

Edit the Outdoor Air information

Can edit heating/cooling setpoint temperatures, but generally easier to edit these in the energy modeling tool

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Inspect Model Geometry

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Troubleshooting

When uploading the gbXML file created in Revit to GBS, GBS may crash and not successfully upload your model

Often, the error message won’t provide any assistance in identifying the origin of the error

To find the error in your Revit model, employ a method called “Divide and Conquer”

Start by splitting the building in half and try uploading each side to GBS Whichever side crashes while uploading to GBS, continue splitting the

model and repeat the process until you find the error If both sides of the model crash GBS, change where you split the

model.

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Creating a DOE2 Energy Model

There are two classes at this Autodesk University the focus on the creating of a DOE2 energy model in eQUEST:

MP3765-P Using BIM to Streamline Your Energy Model Workflows by Jeff Olden

MP3784-P Calibrating an Existing Building Energy Model by Lauren Kuntz

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BIM Geometry for Daylighting

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BIM Geometry for Daylighting

Many projects can use the geometry created for the energy model to create a daylighting model.

In some situations, the geometry needs to more accurately represent the physical layout of the space within a building:

Slanted or other non-horizontal ceilings used for daylighting or other architectural purposes

Spaces with daylighting shelves Projects where the impacts of furniture need to be taken into consideration

For these, create a separate Revit model and modify it accordingly The rest of the process will remain the same

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Adding a Slanted Ceiling

Create a level at the lowest point of the ceiling and an associated view In that view, click on “Place Ceiling” under the Architectural tab Set the offset to 0’ and select the top boundary of the ceiling to set the slope Edit the slope designed at the boundary and finish the ceiling Check in a section view to see if it has been modeled correctly; you may need to go

back and edit either the ceiling’s slope or offset

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Model Setup in Revit for Daylighting

In Revit, think about how the model is going to be used and how the geometry should be created to support that outcome

For daylighting, utilize the series of 3D views of the various building components created in the template file to isolate like materials for exporting to FBX files.

Understand the appropriate level of detail needed in the Ecotect model Give consideration to the amount of curved/rounded objects in a model; affects file

sizes and time to import geometry Consider how these items impact furniture/major fixed equipment and file size of your

model

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Revit to 3ds Max Design to Ecotect Analysis

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Exporting to 3ds Max Design

In the Application pulldown menu in Revit, select Export > FBX

This will export out each 3D view of like materials into an individual FBX file

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Model Setup: 3ds Max Design Currently, 3ds Max Design is a translator for the FBX

file exported from Revit to a 3DS file imported into Ecotect Analysis

Before importing/exporting the models, ensure the project units are set up correctly

From the Customize pulldown menu, select Units Setup:

Set Display Units Scale to US Standard: Feet w/Fractional Inches 1/32

Set System Units Setup 1 Unit – 1.0 Feet

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Model Setup: 3ds Max Design

To import the FBX models, go to the Application pulldown menu, select Import>>Import and set Files of Type to Autodesk (*.FBX) and hit OK when the FBX Import dialog box pops up

To export, go back to the Application pulldown menu, select Export>>Export and set Save Type to 3D Studio (*.3DS) and hit save

In the dialog popup, uncheck the box for “Preserve Max Texture Coordinates”

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Ecotect Analysis Model Imports

To import the geometry from the .3DS file created in 3ds Max Design, go to:File>Import>3D CAD Geometry… Files of Type: 3D Studio (*3DS, *ASC, *PRJ) Remove Duplicate Faces Auto Merge Triangles Scale Objects By: Feet >Millimeters (304.8) Material – Leave it set to <<Guess>> Zone – Leave it set to <<File>> Import Into Existing

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Model Setup in Ecotect

May need to redefine the origins of your model geometry in Ecotect This requires defining the ground plane:

Use the “Set Origin” button in the toolbar Define a point in the model to serve as the origin “Reset World Origin”

Go to the Modify pulldown menuSelect Transform OriginReset World Origin

If you didn’t specify True North in Revit, do so in theProject Page

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Material Assignments

To apply the specific material that has been created, go to the 3D Editor Page

In the Zone Management Panel: Right click on a zone in the model Right click and choose “Select Objects On”

In the Material Assignments Panel: Select the appropriate material Select Apply Changes

**To learn how to complete a daylighting model using Ecotect and Radiance, refer to the 2011 AU class MP4568-P by Brian Skripac

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BIM Geometry for CFD Models

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BIM Geometry for CFD Models

Anything hidden in active 3D view won’t be included in Simulation CFD Use visibility graphics or the hide tool to hide categories of elements Avoid small offsets between geometry; use join and align to eliminate

small gaps Columns and beams can generally be omitted Fine features on furniture should be excluded (i.e. small diameter

tubing, railings, rounds, fillets, holes, etc.) All models need a surrounding mass volume to represent the air

surrounding a building

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Wind Driven Models

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Buoyancy Driven Models

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Revit to Simulation CFD

Go to the 3D view where you want to use as the basis for the CFD model

Go to the Add-ins Tab and Launch Active Model Alternatively, you can export the view’s geometry as the .sat type of

CAD file and import it into Simulation CFD or Simulation CFD 360

**To learn how to complete a CFD model using Sim CFD 360, refer to the 2012 AU class MP3397-P Taking Advantage of BIM for CFD Modeling.

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Revit Families for Linking to Databases and Spreadsheets

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Building Revit Families Refer to Revit’s Wiki help for

detailed documentation on how to create Revit Families

Use Reference planes and Dimension Labels to adjust the dimensions of geometry

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Connecting to an Access Database Refer to Revit’s Wiki help for detailed documentation on how to install

and use DB Link Use Reference planes and Dimension Labels to adjust the dimensions

of geometry Limited selection of parameters that are editable in the database.

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Autodesk, AutoCAD* [*if/when mentioned in the pertinent material, followed by an alphabetical list of all other trademarks mentioned in the material] are registered trademarks or trademarks of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document. © 2012 Autodesk, Inc. All rights reserved.