Describing a group of windows?
Solution 1:
I think a row of windows would be most recognizable. People would infer that the windows are horizontally side-by-side.
Another word that comes to mind is clump, but that could mean vertical and horizontal. You could specify it and say that: Along each floor, windows are clumped together in groups of 5.
To go along with the updated example,
"Please look at the 3rd clump of windows from the left..."
Solution 2:
In your question, you say:
Note that from a construction point of view each of those five is made up of multiple frames, pieces of glass (or "glazing units"), etc. but that lower-level of detail is not what I am trying to describe.
I think the common phrasing you're looking for is window panes.
For the sake of argument, let's say that a window is whatever single piece of hardware that is delivered and installed. Let's also say that we have four windows, each with three vertically aligned window panes, that are installed next to each other. We then have four windows. But next to those four windows, separated by brick, cement, or another building feature, is another four windows.
In this case, the use of arrays or banks becomes more understandable.
Graphically, it would look like this, where each [] is a single unit that was delivered and installed—and which contains three vertically aligned panes of glass:
[][][][] [][][][] [][][][]
[][][][] [][][][] [][][][]
[][][][] [][][][] [][][][]
Or, with an actual picture:
The way I would describe this is as follow:
A 3x3 grid of four-window groups.
I'm saying grid only because that's a common way of expressing the geometry of this kind of layout. In the phrasing you introduced, it would be array.
I'm using the word group (or grouping) to describe each set of four horizontally adjacent windows. In the phrasing you introduced, it would be banks.
In your phrasing, you had an array of window banks. In my phrasing, it's a grid of window groups.
Or, if you don't like group, you could use set, which I also used when I said that a window group described "each set of four horizontally adjacent windows."
Additionally, you can say either a window group or a group of windows, depending on which sounds better given the surrounding text of the sentence.
In short, returning to the sentence in your question, I would say:
"Please look at the 3rd group of windows from the left . . ."
Or, if I were describing something from the example I provided:
Please look at the top-left group of windows.