Need to know what is required to get your building geometry from Revit to cove.tool without complications? This article will cover every aspect of the Revit modeling process and provide guidelines for best-practice modeling procedures to set up an energy and daylight model in cove.tool.
Before We Begin
The Geometry Plugins are BIM extensions that make exporting building geometry, a quick and accurate process. By automating 90% of the workflow, cove.tool gives the time it takes to set up and run a simulation, back to the designer. Make sure you have the most recent plugin version to use this feature.
What Geometry is required for a cove.tool project?
Cove.tool runs various types of building performance simulations, each requiring their own set of specific project values in-order to output accurate results and analysis diagrams. The elements that require geometry values for cove.tool simulations are as follows: Roofs, Floors, Exterior Walls, Windows, Building Height, Skylights (optional), Interior Walls (optional), and Shading devices (optional). If your Revit model contains these objects, then you have the components required to make an accurate analysis model for cove.tool. Having these elements is only half the battle. The other half is making sure that those objects are compatible for the automation and export process required of the plugin tool.
The next section will cover all the components required to assign the appropriate model properties and useful tools and tips for setting up these elements for an error-free export.
In Revit, roof objects should be categorized in the Roof Family category. In a analysis model, roof objects are defined as the insulated top surface of a conditioned space which protect against solar radiation and heat gain.
Things to note while modeling, roof objects for cove.tool should not be connected to other objects, such as floors, overhangs, canopies, and cantilevers. The roof object for cove.tool must only depict the cap of a thermal envelope. Although many firms have a set practice which requires BIM modelers to use as few model objects as necessary for a project, a users should attempt to separate capping roof object with the rest of the cantilevering, shading, or barreling building components. While preparing for an energy model, or even calculating roof area for internal reasons, having these objects joined can cause inaccuracies and over estimate results.
Objects in these categories, 1) need to be in the Wall Family in Revit, and 2) need to have their function property set to Exterior. Exterior walls, like roofs, are defined as the highly insulated, up-right enclosing elements of a conditioned space which protect against solar radiation and heat gain.
Exterior Walls FAQ's
- (User) Should shading elements be modeled as Exterior Walls object?>No items like Fins, Overhangs, Louvers, Cantilevers, and Balconies belong in the Shading Devices Layer. If your Exterior Wall objects are joined to these elements, users are recommended to separate them, and layer them as separate.
- (User) I have been told that spandrels go in the window layer, but my spandrels have insulation, and are not just opaque glass, so don't these belong in the wall category?>95% of the time spandrels will more aptly represent thermal bridging closer in the range of the glazing, then that of the exterior wall. The 5% of cases where spandrels would better be placed in the window layer is high insulation.
BIM modelers should not allow exterior walls to continue beyond the envelope, that means dividing a wall which continues inward and transitions to become an interior walls. Interior Walls have their own category and including them in this export will be problematic when assembling the thermal envelope. Curtain walls are also a typical family tag most Firms use to model their exterior walls, especially when the building envelope is predominately glazed. This method is not encouraged as it can become increasingly difficult to select and/or separate your exterior wall objects and the glazing elements. Curtain Wall will automatically filter into the Window category, so to have them appear in the exterior walls view would require extra steps as seen in the Revit Plugin Tutorial.
Window objects can be classified by their lower performance insulation properties (i.e. U-values is equal to 1/R-values), and are mostly attributed as holes in the project's thermal envelope. Because they are a major factor in the envelope's bridging, transfusion, and infiltration attributes, it is important to accurately depict the amount of glazing and wall surface area, or WWR % (window-to-wall ratio), in a project. Also note that although windows is an element categories with a translucent material properties, it is not required that they be strictly translucent, not opaque, or a traditional glazing material. The most important criteria for determining whether it belongs in the window layer or not is that are on the building envelope layer, and that their insulation properties are considerably lower than that of the exterior walls. Therefor objects like exterior doors, mullions, and spandrels will fall under the window layers export umbrella. The amount of daylight/radiation they can obstruct will make nowhere near the impact on the building's EUI (Energy Use Intensity), then holes in the thermal envelope (which will affect heating/cooling/fans and more).
Window objects can belong to a couple of different categories in Revit. A BIM modeler may label a window-object as a Window, Curtain Walls, and/or Curtain Panels. Three Revit Families to stay away from when modelling this category is the Wall Family, Curtain Systems, and Generic Models. Windows with Window, Curtain Wall, or Curtain Panel tags, should have no issues as they are already correctly marked, and will be automatically filtered into the cove.tool window's view. If your Window object is in the Wall or Curtain System category then your object should just be un-hidden in the cove.tool window view. These object types will have their area values properly exported once visible, no matter the family tag. However, if you repeat the 'create cove.tool views' command, these objects will again be filtered out and you will have to repeat the un-hide step to return them to this view. If your window object is in the Generic Model Family, then the views command or export tool will not read this object, or be able to export area data, because this object type is a composite file in Revit which has linked or embedded area information that the plugin cannot pick up. Even though Generic Models objects have a height and width components, they do not provide a variable which can be used identify surface area. These object, in order to properly export with the plugin, should have either their family tag change or be remodeled as an compatible window object type.
Last, exterior door and window-tagged mullion objects will also show up in the automated generation of this 3D Export View. As for an energy model equation, those areas are used in the EUI calculation for glazing area and should be categorized as window objects because of their poor insulation properties. Also, if these elements did not show up in the 3D View, do not hurry to include them as these objects can be included in the show up in your windows-view.
(User) Why do spandrel objects go to the window category?
> Spandrel's which are made up of a poorly insulated panels belong to the window category. Use an area weighted average u-value to take them into account.
(User) Spandrels make up 50% of my projects total glazing area, and they have a a very different U-Value from my projects normal glazing product. What values should I use?
> Do an area-weighted average of the two U-Values to calculate the value you would want to use in your cove.tool project. No matter the difference of these two values, they will be far nearer in value then the Wall R-Values. Also, for an early stage simulation, this will be more than enough to make an apples-to-apples comparison of its impact on the overall design.
(User) How do I let cove.tool know I have Dark Colored Glazing/ Treated Glazing?
>Users should import the glazing as normal, then once inside cove.tool adjusted the glazing properties to reflect their product's visual performance. For the Daylight model that can be done in the right-hand control panel, under the "Visual Transmittance" input. For the energy mode, in the baseline page under the envelope tab, in the U-value, SHGC inputs.
(User) Should I import interior glazing, not just envelope glazing?
>No, interior glazing geometry should not be included in the window surfaces export. Only glazing elements on the building envelope should be included. Interior glazing objects are typically the most transparent (>88% VT) products and thus can be reasonably indicated by leaving the area open for demonstrating daylight penetration.
Skylight objects should be modeled with the Skylight Family Tag. Modeling them in any of the other glazing related families, will not cause any headache but they will not automatically filter into the Skylights 3D View. Users will have to select them manually with the Reveal Hidden Elements (light bulb icon) tool, to unhide them in the cove.tool' skylight view. Skylights will be categorized similarly to windows but as horizontal geometry. Also note, not all projects have skylights, so if your project does not include geometry for this category, then leave this section empty.
(User) My skylight is a vertical clerestory, is this still considered a skylight?
>Vertical panels would actually be modeled and exported as windows. In an energy model, this would be the category in order to be accounted for the context obstructions. Keep the skylights category for horizontal laying, or angled (<45 degrees) glazing elements.
The cove.tool' shading device layer will typically load as an empty 3D view. This is because shading elements can originate from any Revit Family Category and automating the 'create views' process can be difficult. So instead, the plugin process for this category is to reveal the shading elements. Compatible categories for shading devices can be floors, walls, roofs, curtain walls, and sweep objects. Moving any of these elements to the shading device layer will make for a compatible export.
One model method which is not compatible with the plugin process is geometry of perpendicular components. Perpendicular geometry is modeled elements that have a horizontal plane and vertical plane embedded into single objects. Example include a curtain wall object with branching planar geometry. The objects are problematic for the plugin because they complicate the area and coordinate recording of the project.
The plugin is not able to accept elements with perpendicular geometry embedded into a single object. This is also causing the shading elements in your model to not export. The objects should remain either vertical or horizontal planes. The shading objects are modeled in a vertical category but used the horizontal component to model wide mullions. Once I replaced your curtain walls with a generic glaze property and no mullions or Grids, the area was able to easily export and run the daylight.
Shading Devices FAQ's
- Spandels? - opaque spandrel objects belong in the shading device layer. However, if the BIM modeler have these elements take the place of building envelope, then they should also be exported in the windows layer.
- Doors? - Exterior doors belong in the windows category, interior door should not be included in any export. If your door is opaque, it still belongs in the window layer, but can also be imported in the shading device layer to include daylight
- Louvers (ventilation screen)? - Export as part of the exterior wall, they are account in the building's engineering inputs, not as part of the project massing.
- Louvers (shading screen)? - Export as part of the shading device layer.
- Frit (shading strategy)? - Do not include in geometry export. Can be replicated with the Visual Transmittance (VT%) input for glazed building objects by using an area weighted average.
- Mullions? - include in windows category.
- Interior Window Blinds? - Do not export unless they are large and modeled include in shading device layer. If not just enable interior blinds in the engineering inputs. Family type cannot be Model Group or Generic Model as element will not export. Highly Triangulated geometry will cause the simulation to crash to be wary of exporting blinds.
- Curtains? - Do not export. Use the blinds/curtains input in the energy inputs page.
- Interior Shades? - Do not export as this is not appropriate for a daylight model.
- Operable Shades (louvers, screens, awnings)? - Kinetic elements cannot be accurately simulated in the cove.tool 3D Visualization because it is an annual metric. They can be accounted for in the energy model by going to the energy inputs page.
- Cantilevers? - Include in the shading obstruction layer. If you cantilever is connected to a floor or roof object, separate the elements before export and place them in the appropriate export layer.
- Balconies? - Include in the shading obstruction layer. If your balcony is connected to floor or roof objects, separate the elements before export and place them in the appropriate export layer.
- Building Context? - Neighboring building context can be exported in the shading device layer. Keeping these elements simple is key, as in to scale block models would be the recommended path.
- Trees/ Deciduous Trees? - Simplify geometry by making cubes that approximate the size of each tree. Do not model spheres or other complex geometry as this will slow down the simulation and will not increase accuracy. Make sure these cubes are visible on the shading view or layer.
- Vegetation (Miscellaneous) - Simplify geometry to cubes, then move to shading device layer. Again, heavily triangulated geometry is not a smart idea for the export. This will considerably extend the run time for your daylight analysis.
In Revit, floor objects are identified by their Floor Family categorization. In a analysis model, floor objects are best defined as surface area which bounds a conditioned space from below, and the best indicated for regularly occupied and conditioned space. Be wary of having multiple surfaces indicate the floor are on the same plane, as they may double-log surface areas and will result in double-counting the project's square-footage calculations thus result in many incorrect results and input which depend on a sqft-unit factor. Another item to look out for is export the roof object as a floor, that would result in a bright red surface area above your project in the 3D Visualization and thus an inaccurate sDA%/ASE% result.
(User) One of my floor objects extends out to be roof area on an adjacent space, and/or extends out to be a cantilever, should I separate the geometry to make the floor area distinct from roof and shading device categories?
> Yes, floors should only indicate area of conditioned space. If your geometries extend out of the thermal envelope. Unpin the geometry and redraw the outline to separate the geometry. Hide and reveal geometry to the correct layers accordingly.
(User) For LEED Daylight compliance, the credit language says to not include typically unoccupied spaces for the daylight simulation. Therefor should I not include this floor area in the floor geometry export?
>Yes, if you are strictly using cove.tool to explore Daylight for LEED, then separating regularly occupied and typically unoccupied spaces will be required. Also, LEED Language requires the analysis to use a 2ft Grid Size, so this input would also need to be changed.
(User) I used floor objects to model my project's roof and shading devices, is that OK or should I remodel them?
>This is fine, for rapid results managing the visibility of the objects in the different Revit views will ensure an accurate import. Make sure the same geometry is not exporting in multiple export views.
In Revit, interior wall objects are identified by 1) their Wall Family categorization, and 2) their "interior" function property as seen in the Edit Type Window.
Interior walls object are not necessarily going to be used for the energy analysis model, but rather are crucial for modeling the conditions in the daylight model. The amount of daylight obstruction your interior walls provide will the impact the sDA%/ASE% of your project, which may in turn impact your energy results if your project has daylight sensors and has the ability of receiving energy benefit from a highly daylit design.
Users do not need to worry about the number of interior walls in their project as area is not being recorded in the final export, only their Cartesian position in space (this is also true for shading devices). Also, BIM modelers should not have interior wall elements which continue beyond the envelope and/or convert to becoming exterior wall - envelope geometry. If so, they should be separated at the thermal envelope seam and filter accordingly.
Interior Wall FAQ's
- (User) Is a column considered an interior wall? Will columns show up in my export?
>No, the column family is not automatically revealed in the "create cove.tool views" process. However, users are recommended to include these items by revealing them in the interior walls layer and exporting if they are large enough to obstruct the daylight map.
(User) Are my interior glazed partitions going to be included in this view?
>No. Interior glazed partitions, glazed door, or partition windows should not be included in any of the export categories. They are typically the most transparent (>88% VT) glass products and thus can be reasonably indicated by leaving the area open for demonstrating daylight penetration.
(User) Would stairs, furniture, cubicle partitions be included in this export?
Do not do this as this is not how professional daylight analysis is done and it will greatly add to the simulation time for no purpose. Especially in the case of highly triangulated geometry like furniture models. For Stairs and cubicle partitions which are more permanent elements, these can be added in this layer or in the Shading Device Layer, as they do provide an amount of daylight obstruction and could provide energy savings. Again, avoid high geometry elements as a daylight ray must be run to each triangle.
Building Height Export
This measurement will be automatically be recorded by the Revit Plug-in once selected. Note that the building height export should be the vertical measurement of the lowest point to highest point of conditioned space, for more information see here. If your building height displays incorrectly, check this article to see why.
Mixed Use Project
User can check out how to create a mixed-use project in this article. The process of creating a mixed-use project with the plugin can be seen here, note that the video tutorial uses an older version of the plugin but carries the same principles for making a mixed use project, i.e. duplicates of the 3D Views for each use-type.
Only include geometry from the parking structure if the space is conditioned and would make up a considerable percentage of your overall lighting load. Typically we recommend not to include these spaces. If you do include it you will need to set it's system to not use heating and cooling and adjust the mechanical ventilation. Also the wall areas should not be exported and their values set to 1 since there is not thermal envelope. There are several more inputs that should be done in collaboration with an engineer.
Interior Architecture Study, Renovation, or Modelling Addition with Existing Project?
Modeling a renovation/addition project varies somewhat on a case-by-case level. It really depends on how much of the project you would like to encompass into the analysis (ex. only renovation, or both existing+renovation), what kind of information you have on the existing projects (ex. BIM Models, Past Energy Reports, knowledge of existing construction), and if your design is only interior, single or multiple levels, or an entirely separate wing with the only connection being a transitional space.
Answering those will help clarify how you should proceed. As far as setting up a model for geometry export, best practice is to only include area & building elements that directly depict the analysis space. For example, if you are renovating only the 1st level communal/lobby space in a multistory tower, and this program is only along the southern facade. Then the model would only have the floor area that bounds the lobby space, a south facade with wall and window objects and no roof objects, since the definition of a roof object requires direct radiation from above. Also to set up the energy benefits from a shaded space, you would place lobby ceiling in the shading device layer, and include interior walls that shade and bound the rest of the space.
If this makes sense then feel free to start setting up your model and reach out to the support team on livechat as other questions arise. Sending the team model images and project details about your project will help discuss your analysis in further detail.
Parametric Designs (script-generated)
Just make sure the elements fall in the correct families as specified above. One red flag to look out for when generating custom geometry in Revit, elements intended for cove.tool export should always have area information in their properties panel. Items which do not display area out-front, will likely not be accepted by the plugin.
**For other Revit Plugin related articles, also make sure to check out the Plugins Page. To use the Revit Plugin from cove.tool, make sure you have installed the latest version and are using Revit 2017 and later.