Most kit gyroplanes with windows or windscreens use polycarbonate plastic commonly known by the trademark name of Lexan. This plastic is extremely strong, good in weight, and not as suseptible to chemical damage as some other types of transparent plastics. It also has excellant optical clarity.
Lexan can be damaged from scratches if care is not exercised when working around the window. It is not totally immune from chemical damage and proper precautions should be used to keep your windows in top shape.
When cleaning plastic windows first rinse with plenty of water. This will rinse off loose debris and soften bugs and grime. Use a soap solution like you use for car washing. Do not use dish or laundry soap, as these are way too harsh to be putting on windows. Loosen stuck on bugs and minor debris with a fingernail with water running (rinsing) over the spot while you clean. Dry with a clean dampened chamois or soft cloth. Do not use paper towels- they scratch. A polish, wax or sealer may now be applied.
If you have small scrathes in your windows there are products and kits available to remove them. Larger scratches require someone specially trained to get those out or you may have to replace the window.
Something to consider when installing your windows is how they are mounted. My particular kit had called for mechanical rivets but I know from experience that a window will need to be replaced. I opted to get some stainless steel (CRES) hardware in place of the rivets. The hardware will not only facilitate for easier removal later but also saves the fiberglass stucture ( from drilling out the rivets) in the long run as well.
Window polishes and plastic cleaners made for aircraft windows are your safest and best defense to protect your windows.
This section on structure should have given you a bit of an idea of what to expect in this portion of your build and maybe given a couple pointers to think about. There are still many things that have to be accomplished before we get in the air so lets get our passion in a different area- the Electrical Installation.