Let’s begin by defining aluminum storefront window systems. These are the modern window systems typically used on the main level of your storefront. They are square in section and frame a double insulated window.

Here is an example of a traditional single pane window system. The metal housing is thin with a narrow profile. The sill flashing overhangs the lower wall system and is normally pretty flexible. The window sits toward the outside of the exterior wall.

Condensation issues are common with these types of windows, especially if a heating vent or source is not nearby. Because they are single pane, cold and heat transfer is great. The frame does not have a proper thermal break (material that prevents heat and cold transfer across the system) so it is also very economically inefficient. If you are taking off a slipcover or doing some significant work on the upper section of the façade, these windows have a hard time surviving the improvements. Space between the frame and the top of the window is typically tight. Façade movement will crack the window. I have even experienced a total outward explosion of the glass due to the pressure applied. Most often, however, it simply cracks.

Aluminum storefront systems are readily available from a number of different companies. They are a very good solution to your main level windows. I don’t recommend using them at any other location of your building. The system is easily assembled in the opening. Don’t worry about getting an exact build on the opening; a good window company will verify the size prior to ordering. The frames are cut onsite. These windows sit about 2” inside the wall, so you should expect to design a sill cover at the bottom edge. The window installer will often create this sill with the same color and material as the window so it appears seamless and clean. The jambs and head usually has an angled edge trim that will be caulked in. Your caulking should be a color that matches the frame. Historic Preservation does not like you using silver color, known as “clear anodized.” Unfortunately you are limited to standard colors.