I bought a third-story vintage condo with casement, double-hung, and clerestory windows facing a dirty street and a courtyard. Some of the windows are so large I can't even wrestle the storm windows out to clean them. (The previous owners hadn't cleaned them in awhile either.) The man from Service Building Maintenance was prompt, friendly, and efficient. He made short work of each and every pane of glass with an arsenal of squeegees and left me with a bill that was less than I expected. I'll be calling this company every year to keep me sparkling clean.