Twin Double hung would the proper descriptor for what you are describing. When you put two windows together (i.e. mull two units) it is done with a mullion strip or clip that attaches into the exterior accessory groove of the outside and inside. If you are creating the rough opening, you can just give whatever manufacturer you are ordering from that measurement and they will create the twin unit that will fit that opening. It will be factory mulled which is preferable most times anyway.

Thanks for the reply! I may have used the wrong term - I guess it is called "column" as well?? I'm referring to the angled piece directly to the left and right of the cooktop cabinet. The "column" looks to be slightly narrower than the flat angled piece that it is attached to. I'm assuming the column has been cut in half and the halves used on each side. Sorry!

Ok, I think different people are talking about different things. A valence is a short drapery panel that only sits at the top of the window. It is installed with either a curtain or drapery rod or stapled to a back board, and is usually paired with blinds but can be hung alone. What Angel and Justin have pictured are blinds which can be raised and lowered, not valences. I think that the window that Justin shows is not the right dimensions to support a valence and the blind he mentioned. It'll look odd with that window. Justin, IMO you should just hang the blind and skip the valence. A valence won't add anything and will decrease the natural light into your kitchen. I wasn't certain what you meant by "horizontal blinds" - a slatted blind? Perhaps a fabric blind would be softer. And sufficient.

I would prefer that shed roof above the three windows extend across the entry with no posts or gable. They look mal-proportioned in every way and the more "ditches' around gables, the more potential problems with rain/snow melt. Just extend the shed a bit deeper to cover more of the windows, porch and step. No posts, rock pillars or gable and timber trim. Consider unifying all the gables or it will become too busy. Put in a gorgeous front door to draw all the attention and be sure any lighting is sufficiently large to make a statement.