John's Window Capping
In some cases sliding windows can be an acceptable choice if they are well maintained and weather-stripping is kept in good repair. Although not the most energy efficient example of modern window technology they can serve the homeowner well for many years with no trouble. Consider cladding this style of window to ensure a proper seal to minimize air infiltration and reduce draughts.
The high maintenance area on this style of window is the brick mould wood frame. Cladding will eliminate the need for paint and can be the answer when attempting to integrate existing windows into a building that has received a new style of window. The cladding can be the element used to tie the new in with the existing.