Sash Windows


Generate and automatically fit a huge range of sash (double hung) window designs using this parametric (14 user defined parameters) windows builder. Each sash within the window frame is a separate piece of geometry and can be animated, if required.

This tool generates and places multiple sash windows, of the same type and size, at once - maximum of 50 at a time. In addition, basic materials and partnames are automatically assigned to save you time and to aid selection.

You can also use this tool to build a horizontal slider type window. See tips section, below.

How to useā€¦

  1. Select one mesh item
  2. Select one or more quad polygons (of the same size)
  3. Set options
  4. Click “Build and Fit Windows”

User Interface



Reset Values
Reset values to their default. Note: Click this reset button before using this tool for the first time.
Frame Size
Sets the thickness of the top and sides of the window frame.
Cill/Sill Height
Set the thickness/height of the base of the window frame.
Controls how far the window frame will sit from the front (face) of the wall geometry. For example, a value of zero will mean the frame of the window sits flush with the wall. Positive values push the window towards the inside of the building.
Add Border Polygons
Adds four polygons around the outside of the window. Useful if the window protrudes from the wall.
Top-Bottom Split

The window contains two sashes. This value determines how much of the space inside the frame is assigned to each of the sashes. Changing this value allows you to create large sash windows with a historical apperance. Most modern sash (double hung) windows use a 50/50 split.

Inset Into Frame

Controls how far the sashes are inset from the front of the window frame. Use a value greater than 13mm (1/2 inch) to add definition to the windows - 25mm (1 inch) is a good starting point.

Sash Frame Size

The thickness of the frame around each sash within the main window frame.

Bottom Rail Size

The thickness of the bottom (rail) of the lower sash. To create a more attractive window use a value greater than the “Sash Frame Size”

Meeting Rail Overlap

The overlap between the top (upper) and bottom (lower) sash can be set to be the same or half of the size of the “Sash Frame Size” value.

Glass Thickness

Set the thickness (depth) of the glass. For single glazed windows like these a value between 3mm and 6mm is appropriate.

Panes:Top and Panes:Bottom
Set the number of panes (sections) for each sash of the window. A of choice of 12 pane layouts is provided for each sash:
  • 1
  • 2 (2 x 1)
  • 3 (3 x 1)
  • 4 (4 x 1)
  • 4 (2 x 2)
  • 6 (3 x 2)
  • 6 (2 x 3)
  • 8 (4 x 2)
  • 9 (3 x 3)
  • 12 (4 x 3)
  • 12 (3 x 4)
  • 16 (4 x 4)
Muntin Style
Muntins (or glazing bars) are the grids that divide each sash into separate panes and two styles are available: A standard tapered profile or a simple box profile.
Muntin Size
Sets the width of the muntins. Choose from one of six sizes that range between 13mm (0.5 inch) and 32mm (1.25 inch).
Delete Locator Polygons
Delete the polygon selection (that was used to tell the script where to build the windows) after the windows have been created.
Build and Fit Windows
Apply the tool. Create a sash window at each location where a polygon is selected.


The size of the window is taken from the height and width of the first selected polygon, from your selection. The remaining polygons in your selection are only used as position/orientation locators.


  • You can build slider type windows using the technique shown in the video below.
  • You can divide the individual panes of the window geometry using mARCH's handy Muntins/Glazing Bars tool.

Note: The video below shows an older version of the sash windows UI (formerly known as “Windo” for modo).


  • Only supports building of rectangular windows.
  • Selected polygons must be quads i.e. contain only 4 vertices.
  • Does not support X-up axis coordinate space.