Entering Transom Windows

So many new homes are using transom windows to add extra light in the rooms. In addition to the more light, however, these windows also bring in more heat from the solar gain. It is important to make sure you include them in the load.

Accounting for a Transom window in RHVAC is fairly straight forward. Simply add the window on another line in the glass section. Make sure you change the material type to be a fixed window.




Just a word about U-Values and SHGC for unique and decorative windows. If your project has something like a stained glass window for either the window or a transom, you may find it a little difficult to find the U-Value and SHGC using an internet search.




Here we have a transom over each of the three windows on the on the south wall.



Drawing the transoms in Drawing Board I just as simple.

Here’s our drawing. We have two windows and a double French Door. There are transoms above all three.

To add the transoms, grab your window object in the catalog browser. Drag and drop it on top of one of the windows.

You can see the second window above the original window. In this example it isn’t quite lined up. We can click on the small yellow dot in the middle and line it up correctly. But before we do that let’s make the modifications in the Object Properties box.

First, we need to change the material from an operable window to a fixed (or whatever is the appropriate glass for your project.)




Now change the size. Our window is only 18” high and the entire width of the window below.


With this glass set, click on the right mouse button and copy glass.

Put your cursor over the other window, click on the right mouse and paste the glass. Now line the two transoms up with the windows below.

Next, put your cursor on the wall close to the French door. Click on the right mouse button and paste the glass. Change the size of the glass to match the size of the French Door and then move the glass over the French Door object.

Another tip – if there is an overhang you want to put in the regular windows, enter the overhang information before you add the transom glass. If you don’t then you will need to move the transom out of the way to get to the regular window, then move the transom back and enter the overhang information for that.







Make sure you get the overhang offset right. The overhang offset is the distance from the bottom of the overhang to the top of the glass.  It will be different for the window and the transom.








In this example the overhang offset for the glass and glass doors is 4.5 feet. The offset for the transom windows is only 28”.


This is an example of the entry for the windows and French door. Notice that the projection is still 3’6” but the offset is 4’6”.

Leave a Reply

Your email address will not be published. Required fields are marked *

Powered by: Wordpress