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Where does the model information come from?

2D CAD and image import

In IDA ICE it is possible to import CAD objects and image files. These can be used as a base when creating the simulation model, or as shading elements that cast shadows onto the simulation model. There are three categories of CAD objects and image files; building information models (BIM), CAD and vector graphic files, and image files.

BIM files contain 3D geometry as well as properties for rooms, walls, windows and materials etc. An IDA ICE model, i.e. building bodies, zones and windows etc., can be automatically created from the geometrical information. Furthermore, the properties of objects in the BIM file can be mapped to the corresponding objects in the simulation model. The 3D geometry of a BIM file can also be selected to shade the simulation model.

CAD and vector graphic files contain 3D or 2D geometry. A section of this geometry is shown as lines in the floor plan tab and these lines can be used to snap building bodies and zones etc. in the floor plan. Building bodies and zones can be automatically created from graphic files if the imported geometry consists of volumes enclosed by polygon surfaces. 3D CAD objects can be selected to shade the simulation model.

Image files contain raster (bitmap) images. These are shown in the floor plan tab when the section is close to the location of the image. The images can be used as a background when drawing building bodies and zones in the floor plan or when inserting windows and shading objects in the 3D view.

Supported file formats

BIM

• Industry Foundation Classes (*.ifc)

CAD and vector graphic files

• AutoCAD (*.dwg, *.dxf, *.dwf)
• SketchUp (*.skp)
• 3D Studio (*.3ds)
• Wavefront (*.obj)
• Computer Graphics Metafile (*.cgm)
• Corel Presentation Exchange (*.cmx)
• MicroStation DGN (*.dgn)
• Micrografx DRW (*.drw)
• Gerber File Format (*.gbr)
• Scalable Vector Graphics (*.svg)
• Printer Command Language (*.pcl, *.prn, *.prt)
• Macintosh PICT (*.pct)
• HP-GL/HP-GL2 (*.plt)
• WordPerfect Graphics (*.wpg, *.vwpg)

Image files

• Bitmap (*.bmp)
• JPEG Interchange Format (*.jpeg,*jpg)
• Portable Networks Graphics (*.png)
• ZSoft PC Paint (*.pcx)
• Tagged Image File Format (*.tiff,*.tif)
• Adobe Photoshop (*.psd)
• Truevision (*.tga)
• Windows Meta File (*.emf,*.wmf)

IFC import

In IDA ICE it is possible to import 3D building information models (BIM) via IFC files. Most 3D CAD applications can export architectural data in the IFC format.

The most important information that is transferred is geometrical data, i.e. the shape and position of zones, windows, doors, building faces etc. Zones in IDA ICE are automatically created from so called space objects in the IFC model. It is not sufficient that the CAD model only contains wall objects, spaces that fill the voids between walls must also have been created, a semi-automatic process in most CAD tools.

IDA ICE can also utilize other types of information in the CAD model, such as space types, window types, wall constructions, should they be present. One can find more detailed information about the ICE IFC implementation on the user’s web page: Help menu, Support, Download & info center. Select Documentation on the page and open the document ‘IFC Import’.

Mapping data from IFC

Start with a building without zones and select the Floorplan tab. Press IFC… > Import… to select an IFC file for loading. There are some sample IFC files in the installation, normally located in C:\Program Files\IDA\samples\ICE\IFC.

The first task is to map named data objects in the IFC model (if any are present) to corresponding IDA resources. Press IFC… > Mapping… in the Floorplan tab to open the Mapping dialog. If wall constructions have not been described in detail in the CAD model, select directly Constructions in the Category combo box. This will present a list of all wall types that have been found in the IFC model. Since IDA ICE needs more detailed information about a wall, IFC wall types need to be manually associated with IDA ICE wall constructions. To bind a certain IFC wall type to an IDA ICE construction, select both the IFC wall type and the corresponding ICE resource and press Map to selected. A right pointing arrow in the IFC Data list indicates that the item has been bound. Usually one first has to load relevant IDA ICE resources from the database by pressing Load from Db. To inspect the selected IDA resource, press View.

Repeat the procedure for window types as well. Here, one usually has to first create relevant windows in the ICE database, including internal shadings etc.

If wall constructions have been described in the IFC model with layer thicknesses and material names, one can automatically create corresponding IDA ICE constructions. In this case, one starts instead with binding IFC material names with IDA ICE material resources. Once the materials have been mapped, IDA ICE wall construction resources are created by pressing Import from IFC when the relevant IFC wall type has been selected.

A useful addition, available from version 4.7, is the ability to map IFC space type names to zone templates. This way, if you have created templates for your typical room types, zones will be created with all input data already in place.

Any object in the IFC model which is not explicitly mapped to an IDA resource will be set to its default value, which is given by pressing Defaults on the General tab in the building form.

Changing position of IFC model

The position of an IFC model can be changed in IDA ICE. Press IFC… > Shift… to open the Shift dialog. In this dialog an offset or desired position can be defined for the IFC model.

Create zones from IFC spaces

An IFC model may contain more than a single floor. A horizontal section (slice) of the building at a certain level is shown in the Floorplan tab. To select a different level, press the button Level: xx m, where xx is the floor height from ground of the current level. In the Level dialog, the building height from ground (Building top) and height coordinate of the floor slab with respect to ground (Building bottom) are also shown, as interpreted from the IFC file. These numbers are not always correct for the user’s purpose.

To define which spaces in the IFC model that should constitute a (thermal) zone in the simulation model, click on (select) the neighboring spaces that should be included. (Click again to unselect a space.) Think about zone economy, i.e. do not create more zones than you think is physically motivated for the current study. To create an IDA ICE zone from the selected IFC spaces, press New zone. This will create zones using the currently selected zone template, unless the IFC space type has been mapped to a given template. Try to give as many reasonable defaults as possible for new zones using appropriate zone templates; after creation these values must be edited separately for each created zone.

If you have a good quality IFC-file, you can also - from version 4.7 - instantiate all IFC spaces to zones with a single press of the New zone button without first selecting the space. To do this, select this alternative under the IFC button.

The IDA ICE zones are created from the geometry of the corresponding IFC space(es). If for example a space is taller than the typical floor to floor distance of the building, the corresponding ICE zone will also reach over more than a single floor. One can change the horizontal section level during the zone creation process but it is currently not possible to combine several spaces vertically into a single zone. Note that the Floorplan view displays two models simultaneously, the zones of the created ICE model and the spaces of the IFC model. Both categories of “rooms” can be individually selected and ICE zones can also be opened.

If the IFC model is revised during the ICE modeling project, there is some support for retaining previous work. New IFC models can be loaded while modeling, either replacing the existing model or adding to it, e.g. loading several floors that are in separate IFC files. When a new file is loaded, the user is given the option to replace or add to the current IFC model and to replace or keep mapping information and existing ICE zones.

If the IFC information is incomplete or too complex for some part of the building, the user can simply avoid to instantiate these zones based on IFC background and draw them manually on the floor plan.

Exporting results to IFC

Results from heating and cooling load simulations in IDA ICE can be exported for merging with IFC models. This is done by choosing “Export to IFC” in the Tools menu after simulation of the heating and cooling loads.

3D CAD object import

Import CAD objects as building bodies or zones

CAD objects can be imported as building bodies or zones if the imported geometry only contains a volume enclosed by polygon surfaces (polyhedron) without holes between the surfaces. The geometry should describe the inner surface of the external walls for a building, and the inner surface of the zone walls for a zone. No other information than the pure geometry of the building body or zone can be included in the CAD object. Click Import… on the floor plan tab and choose Import building body… or Import zone geometry….

Imported building bodies and zones have protected geometry, i.e. their geometry is non-editable. However, an imported building body is fully editable if the imported geometry only has one floor and that floor is horizontal and does not contain any holes, and the geometry does not have any outward leaning walls (surfaces with their exterior normal pointing downwards). This is the same kind of geometry that can be created in the ICE roof editor. Importing geometry as zone will also create a building body of the same shape as the zone.

If a geometry file contains multiple polyhedron geometries, each with a separate color, they are imported as separate building bodies or zones in ICE. If surfaces are placed one wall thickness apart, these are regarded as thermally connected internal walls.

Importing CAD objects and images as background

CAD objects and image files are either imported with respect to the building coordinate system, and are then moved with the building if the building is repositioned or rotated, or they are imported with respect to the site coordinate system, and remain fixed if the building is repositioned or rotated.

Import a CAD object/image file with respect to the building coordinate system by clicking the Import button on the floor plan tab and choosing CAD and vector graphic. Alternatively, select Import CAD on the Insert menu while the 3D tab is shown.

Import a CAD object/image file with respect to the site coordinate system by clicking the Import site CAD button on the Site object dialog opened by clicking Site shading and orientation on the General tab. Alternatively, select Import CAD to site on the Insert menu while the 3D tab is shown.

To place a CAD object/image at the current mouse pointer in the 3D view, use Right mouse button menu > Import CAD or Right mouse button menu > Import CAD to site.

Moving and scaling CAD objects and images

A CAD object is automatically scaled and positioned so that it corresponds to the simulation model. The scale and position of a CAD object can be seen and edited by double-clicking on the object. A section of the CAD object or image is shown in the floor plan tab if the floor plan level is within the bounds of the object. Select this section by clicking on it. Move and change size of the CAD object/image by dragging/resizing the section.

A CAD object can also be moved in the 3D view. Select the CAD object, hold down the ctrl-key and drag the object. The object moves in the x-y plane. To move a CAD object along the z-axis, hold down the ctrl-key and the shift-key while dragging.

Shading by imported 3D objects

3D CAD objects can be selected to shade the simulation model. Check the Calculate shadows checkbox in the dialog shown when the object is double-clicked. Every surface of the 3D object that is not fully transparent is included in the shadow calculation. Semi-transparent surfaces are included and shade according to their transparency. Note that it is the surfaces that shade, so for instance for semi-transparent sphere light will pass two surfaces and hence be reduced by the semi-transparency twice.

Storage of CAD objects

By default the geometrical information of CAD objects is saved in the system file (*.idm). The original CAD file is then not needed after the import. However, if a CAD file is big, very large system files can be created and the performance of IDA ICE can be slowed down. Thus, if a CAD file is big, the option of not saving it in the system file is given in the Preferences dialog, which is opened at import. In that case, only a shortcut to the original CAD file is saved in the system file and the original CAD file needs to be saved in the location specified by the shortcut. If the CAD file is placed in the ICE system folder (the folder with the same name as the system), the shortcut is relative and the CAD file is automatically copied with the system to a new location. Otherwise the shortcut is absolute and the CAD file is not copied with the system. The definition of a big CAD file can be changed in the Preferences dialog from the default of 10000 vertices. The Preferences dialog can also be opened from the Options menu.

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