The last time I was discussing Andersen window options with my usual supplier I asked about the 100 series and said to not use them. This is someone I trust; he grew up the son of the largest Andersen dealer in this half of the state and he's now working for the successor to that company.

Because of your post I looked up the 100 series windows and I see clearly why I was warned to avid them. Here are some of my observations:

• General

The 100 series is an all-composite window (PVC & wood sawdust that Andersen calls Fibrex). Its basically built like a vinyl window and the frame depth front to back is 1 1/4" smaller than the 400 series Andersen windows.

• Appearance

I dislike the appearance of windows that place the glass near the exterior trim of the house because they look "bug-eyed". Perhaps they're OK on a modern design but they look terrible on a traditional design. The 400 series places the glass 1 3/4" back from 3/4" thick siding and trim. the 100 series paces the glass 3/8" in front of the siding and trim. The total difference is a very noticeable 2 1/8".

In elevation view, the width of the frame and sash of the 400 is a 1/2" narrower than that of the 100 but the 100 looks much larger because the sash is flush with the frame and the 400 sash is set back 2" from the frame. In other words, the 100 windows have no "shadow lines" so the windows look stuck on the face of the wall.

• Function

The 100 series double-hung doesn't have a moving upper sash nor can the sash be tilted inward for cleaning. For this reason the 100 series only offers a half screen. However, the Tilt Wash version of the 400 series has an epoxy painted sash. This is not very noticeable because there is an unusually large and unattractive glazing stop that covers most of the sash frame.

• Mullion Sizes

Both windows have 3/4" wide applied mullions but the 100 series mullions are 3/16" deep with little shape and the 400 series mullions are 3/8" deep with a distinctive shape.

• Sill design

The 400 has a steeply sloping sill, a drip groove under the lower edge and a notch that prevents water from getting behind the siding. The 100 has none of those features. To prevent serious water infiltration problems I recommend installing a sub-sill below the 400 which might look odd on a protruding flat window..

• In summary

The 400 TW is a well designed middle of the road residential window. The 100 is a builder grade residential and light commercial window with odd features and some design deficiencies.

I cannot think of an appropriate use for the 100 series, however, you haven't told us anything about the style of the house which is ultimately the single most important design consideration.