Yes, it is necessary that you will be home for the replacement. It would be a good idea if you can deactivate all home alarm systems when the crew arrive and clear the way for staff and their tools. You can also cover your furniture and keep your children and pets away from the work area. The windows will be installed about 1-2 weeks after they have been ordered by customer. A professional and experienced team will do their best to prevent any damage from happening but accidents do happen. To decrease the chance of a damage or accident from happening, remove wobbly items like vase, picture frames or floor lamps from the work area. The process of replacement can shake the walls so remove breakable items from walls and working area. Installer crew will bring their own cloths and plastics to protect your floor in the work field but let them know if there are any other surfaces or spaces that you need to protected or if they have to be gentler on that area. Also remove the curtains for replacing windows so you can use them again. But if you have difficulties in removing your curtains or shades, the installed crew will also do that for you, wrap them in a plastic bag and put them back when the work is done.