In this post I want to highlight how Revit determines the Window to Wall Ratio (WWR). Early on in a project this value does not matter on the Revit side, as there is a dynamic input for WWR for each face (N,E,S,W) of the building. Thus, this input can be changed within Insight irrespective of the Revit model and it's settings.
First, let's see how we define WWR when using mass elements. I am using the same mass model from the "Part 1" post. In case it was not clear in that first post, the entire building is represented by a single mass element. That is interesting when you consider the Energy Analysis Model (EAM) resulted in separate vertical walls in the same plane; Exterior Walls and Underground Walls due to the Ground Plane setting in the Energy Settings dialog.
If we want to set a baseline value of 40% (per ASHRAE 90.1) we can do so in the Advanced Energy Settings dialog. Notice the related Target Sill Height and Glazing is Shaded options.
When the EAM is created, we see the analytical windows are added. In this selected example, the window is 201sf and the remaining above-grade wall is 302sf - thus, 40% of the wall is window. None of the below grade wall is considered in this equation.
When this EAM is pushed out to Insight 360, we see the BIM Setting for the four WWRs is 40%.
- TIP: Notice how the BIM Setting always aligns with zero on the vertical scale.
The great thing about Insight 360 is we can dynamically adjust the WWR without needing to go back into Revit and make changes. In the image below, the Western WWR was adjusted to be 95%, which resulted in the Energy Cost Mean changing from $2.13 (sf/yr) to a less efficient $2.25 (sf/yr).
- FYI: The $2.13 value was based on a WWR range between 0% and 95%, and the $2.25 is based on a single input of 95%.
Quick closing tip... if you prefer EUI (kBth/sf/yr) over Cost (dollars/sf/yr), simply click on the circle in the upper left corner.
I have a few more posts in mind related to walls, so please stay tuned...
