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Glazing Thermal Properties in Revit and Insight

Introduction:

In Revit, you can customize the thermal properties of the wall, window, floor, and roof constructions to accurately reflect the materials that you would like to use in your design.

To change the thermal properties of walls, roofs, floors, or ceilings, you follow similar steps to modify the structure of these constructions. But, changing the thermal properties for glazing is a bit different. To change a window or glazing element, you edit its properties and change the Analytical Properties setting to a common glazing type with prescribed thermal properties.

Using these detailed element thermal properties for glazing elements produces a more accurate energy model rather than simply relying on the Conceptual or Schematic Types.

 

This video shows the workflow for changing the glazing thermal properties in the Revit model. 

Workflow Steps:

Open a Project

Set Energy Settings

  • On the Analyze tab, select Energy Settings.
  • Verify that the Use Building Elements mode is selected.
  • Open the Advanced Energy Settings, for Other Options, by clicking Edit.
  • Confirm that the Export Category is set to Spaces (if they are defined in your model).

Enable Detailed Elements Thermal Properties

  • In the Advanced Energy Setting dialog, check the Detailed Elements checkbox.
  • Click OK twice to apply Energy Settings changes.

View the Thermal Properties for a Window Type

  • Open the default 3D view if necessary.
  • Select a window in your model.
  • Click the Edit Type button in the Properties palette.
  • Note the thermal properties listed for this window type in the Analytical Properties section of the Types Properties dialog.

The thermal properties are determined by the type of glazing selected in the Analytic Construction cell.

Create a New Window Type with Different Glazing Properties

  • Click the Duplicate button to create a new window type.
  • Enter a new name. For example, 36’’ x 72’’ Double Glazing.
  • Click OK.
  • Open the Glazing Types menu in the Analytical Construction cell of the Properties palette.
  • Scroll down and choose Double glazing – ¼ inch thick -clear/low-E (e = 0.05) glass

Note how the Thermal Resistance, Solar Heat Gain Coefficient, and Visual Light Transmittance changed to reflect the improved properties of this glazing type.

  • Click OK to apply changes.

The Analytic Construction of each window type used in your model is set independently. To change all windows, you must change this property for each type. In this model, all the windows are the same type, so the change you made will apply to all the windows.

View the Thermal Properties of the Curtain Panel Glazing

  • Hover the cursor over the edge of one of the glazed panels in a curtain wall, then tab repeatedly to select one panel, then click.

The System Panel Glazed type is selected.

  • Click the Edit Type button in the Properties palette.
  • Note the thermal properties listed for this panel type in the Analytical Properties section of the Types Properties dialog.

The thermal properties are determined by the type of glazing selected in the Analytic Construction cell.

Change the Thermal Properties of the Curtain Panel Glazing

  • Open the Glazing Types menu in the Analytical Construction cell of the Properties palette.
  • Scroll down and choose Double glazing – ¼ inch thick -clear/low-E (e = 0.05) glass.

Note how the Thermal Resistance, Solar Heat Gain Coefficient, and Visual Light Transmittance changed to reflect the improved properties of this glazing type.

  • Click OK to apply these changes.

This change to the Glazed System panel will be applied to all curtain walls that use this panel type.

Generate Insight

  • Go to the Analyze tab and click Generate.
    • If the energy model has not already been created, accept the prompt to create it now.
    • If the energy model already exists, choose whether to use the existing model or generate a new one.

Access Results

  • Once the Insight analysis is complete, go to the Analyze tab and click Optimize to access the results in the Insight interface.

The analysis results will use the detailed thermal properties specified, and the As-Modeled data point for the Window Glass factors will reflect the values of the selected glazing types.

In order to see the effects of changing these detailed thermal properties in your Insight results, be sure to do the following:

  1. In Revit, turn on the Detailed Element checkbox in the Energy Analysis settings before generating Insights.
  2. In Insight, narrow the range of the values being considered for the related factors to include on the BIM settings triangle.
The EUI mean will then reflect the detailed thermal properties of elements as specified in your Revit model

 

Exercise:

In this exercise, you are going to use the workflow that was shown to you in the previous video. We will walk you through changing some of the settings, then ask you a few questions about the results and what they mean.

We are going to use the building dataset from the previous exercise. 

Follow the steps outlined below:

  1. Open the E2a_Roofs model in Revit
  2. Open the Location tool and set Project Location
    • Change Project Address to Minneapolis, MN
    • Select Weather Station 32579
  3. For the first energy simulation, we will change all the glazing
    • Save the project as E2b_Glazing
    • Change all the glazing (windows & curtain walls) to “Large double-glazed windows - reflective coating”
    • Generate Insight
  4. Go to Insight.
  5. Create Insight.
  6. Select the following submitted models to compare:
    • SE2a_Roofs
    • SE2b_Glazing
  7. Open the Insight you have just created by selecting the tile.
  8. Open one of the models and create the baseline
    • Set a range or value for the following factors:
      • Operating Schedule: 12/6
      • Lighting Efficiency: 0.3 – 0.7 W/sf
      • Plug Load Efficiency: 0.6 W/sf
      • HVAC: ASHRAE Heat Pump
    • Save this scenario and rename it as Baseline.
  9. Select Back to Insight
  10. In the Model Comparison panel, select the baseline scenario and compare the performance of each simulation.
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