How it works
Two sashes sit in one frame and only the bottom one moves. You slide it up, it stays where you put it, and the top sash never moves at all. That is the simplest operable window made, which is also why it is usually the least expensive way to replace an opening one for one.
Where it fits an Inland Empire home
Riverside tract homes are full of single-hung windows, most of them original. The frame is narrow and the hardware is simple, so a single-hung unit drops into an existing stucco opening without anyone touching the stucco around it. Put them where a wide view and maximum airflow are not the point: spare bedrooms, hallways, the laundry room, the side of the house nobody looks at.
What to watch for
Ventilation is the trade-off. Only the bottom sash opens, so air comes in at one height. A double-hung window in the same opening can drop the top sash to let hot air out near the ceiling while it draws cooler air in low. In a Climate Zone 10 house, where the evening cools off enough to shut the air conditioning down, that difference is worth thinking about in any room that holds heat after sunset.
If the room is a bedroom, the opening sash has to clear the code minimum for emergency escape, and not every single-hung size does. Get that confirmed at the measurement, not after the window is ordered.
On glazing, a replacement window at a Riverside address has to meet the Climate Zone 10 numbers, a U-factor at or below 0.30 and a solar heat gain coefficient at or below 0.23 on most jobs. In west-facing rooms, aim under those numbers rather than at them.
During a stucco retrofit, keep the weep holes at the bottom of the frame clear of caulk and mortar. They are how any water that gets past the outer seal drains back out.