Then it makes sense to choose durable windows that keep out wind and water and that offer high thermal performance. An old window, such as a pane of glass in a wood frame, lets heat escape through the glass itself and through gaps and cracks in the frame. The new frame and the extra pane of glass cut heat loss. Wood frames, plain or clad in vinyl or aluminum, tend to be more expensive than all vinyl. Plain wood, of course, needs to be painted.
Clad wood requires minimal maintenance.
Aluminum is a good heat conductor. In cold weather, heat inside the house travels readily through the frame to the outdoors making the indoor side of the window feel cold to the touch. In a temperate climate, an aluminum frame may be a practical choice, but it won't offer the best thermal protection in cold winters. Better quality vinyl windows have welded corners. Other windows may have corners that are screwed together.