Window-to-Wall Ratio

The Window-to-Wall Ratio (WWR) is the fraction of the above grade wall area that is covered by fenestration, calculated as the ratio of the wall fenestration area to the gross above grade wall area. The Asset Scoring Tool will use either the WWR that you enter, or it will calculate a WWR based on the number of windows, window dimensions, and the wall dimensions entered. A maximum WWR of 95% may be entered.

Note: In the Energy Asset Scoring Tool, every surface with a window must have a valid window-to-wall ratio or the total number of windows entered. To enter these Window properties:

  1. Select a Block or Block Surface to create or edit a Windows layout
  2. Select a Window layout from the pull-down menu
  3. Enter the Number of windows (for Discrete layout) and associated window dimensions, or a Window-to-Wall Ratio (for a Continuous layout).

Name – Default component text and counters are automatically added. This entry may be edited to include other descriptive or identifying text.


Energy Asset Score Inputs for Advanced Window Layout:

Window layout – Pull-down menu selections (see the accompanying Window Layout figures):

Continuous – Manually calculate and enter the Window-to-Wall Ratio. The Edge offset and Sill height of the windows may be added per the following diagram (optional):



Discrete – Enter the number of windows and the width and height of the windows per the following diagram, and the tool will calculate the Window-to-Wall ratio:



Exterior Shading Type – Pull-down menu selections:


No Shading

External Overhangs – An overhang above the wall is used to control the amount of seasonal sun exposure by decreasing exposure in the summer when the sun is high in the sky and heating is not required, yet still allowing for full exposure in the winter when the sun is low in the sky and heating is desirable (see the Shading Types figure).

Enter Height above window and Projection values (optional). If values are not entered, default values will be applied.

Vertical Fins – A vertical fin will cast a shadow whether the sun is on the left side or right side of the fin (see the Shading Types figure).

Enter Fin Depth and Distance Between Fins values (optional). If values are not entered, default values will be applied

Light Shelves – A device for bringing more daylight into a building. Installed as an accessory to a window, light shelves work by reflecting exterior light onto the ceiling of a room. Light shelves can have an inside shelf, an outside shelf, or both (see the Shading Types figure).

Enter Distance from top, Exterior Protrusion, and Interior Protrusion values (optional). If values are not entered, default values will be applied.


Shading Types Figure:


Daylight Controls – Check box: Menu item available by clicking on a building block from within the Construction workspace. Select if daylighting sensors that reduce artificial lighting in response to the amount of daylight entering the building are installed and in use for windows or skylights. Select the Daylight Controls box for Lighting if daylighting sensors are present for perimeter spaces. Select the Daylight Controls box for Skylights if toplighting controls are used in occupied spaces to reduce artificial lighting in response to daylight through skylights.