Why clean screens if the window glass is already being washed? 

Rain pushes trapped dirt, pollen, and grime off dirty screens directly onto clean glass. Leaving dirty screens in place ruins freshly washed windows during the very next rainfall. 

Can pressure washing be used on screens?

No. High-pressure water easily warps aluminum frames, tears vinyl mesh, and pops rubber spline retainers out of their grooves. Pros always use low-pressure or gravity-fed rinsing systems. 

Do professionals clean the tracks and frames too?

Basic screen cleaning focuses solely on the removable mesh unit. Deep cleaning for the window sills, tracks, and frames is typically offered as an add-on service.