I went to the Brigham City Utah Temple yesterday. I took some time to photograph the temple and particularly its art glass windows. If you haven't been, the windows are very beautiful. They are geometric with the exception of the peach blossom windows. As I looked at the windows I noticed one detail that appears to be symbolic in ordinary looking windows.
On the first level the windows are all rectangular. The photo of this door is an example. Around the edge of the first level windows there is a border that has single small squares every so often.
One level up, on the second floor, there are circular peach blossom windows that go into the dressing rooms. On the towers there are also some arched windows. This already shows progressed from rectangular windows to arched and circular windows. Otherwise the windows are very similar in style to the lower level, with one interesting variation - the decorative border glass now has 2 small squares together instead of one. This is also true on the peach blossom windows.
Now go up to the top level of the temple and again you have arched windows with the same geometric art glass. This time the decorative border glass has (as you've probably already guessed) 3 small squares together.
The pattern for the art glass appears to be that one square is used on the first level borders, 2 squares are used on the second level borders, and 3 squares are used on the third level borders. There are several exceptions to this rule. First, the front doors of the temple have 2 squares, probably because the doors are architecturally prominent. Second, the large art glass window on the east side that goes into the Celestial Room has 2 squares on the bottom 1/3 of the window and 3 squares on the top 2/3 of the window.
So what do these squares mean. Well, this is all speculation on my part, but I'll tell you what I see in it. First, one, two and three squares probably signify the three heavens or degrees of glory. Second, having more squares higher up on the temple implies progression. Third, having 2 squares on the lower part of the main celestial room window and three squares higher up signifies progression in the celestial kingdom with various divisions in it (a similar thing was done in the Oquirrh Mountain Utah Temple using stars).
The one, two, and three theme is not exclusive to the art glass windows in the Brigham City Temple. If you look carefully at the molding, tile, picture frames, etc. you will see dots used in the same way. I had noticed this before when I was in a sealing room and thought the temple just used three dots. Later I was using the restroom on the second level and noticed two dots in the tiles. I assumed that they couldn't get three dot tile and had just used two dot tile to give the same dot pattern - until I looked closely at the exterior glass and realized that the two dots in the bathroom tile on the second level was probably intentional.
There are some of my thoughts and insights on the Brigham City Temple art glass and on the dot theme used in the temple. If you would like to add anything, please comment.