What is full glass coverage?
If you just have basic liability insurance, windshield and other glass damage isn't covered. Chances are, cracks and chips are not covered by your collision insurance either. This can vary from one insurance company to another, but for the most part, glass coverage doesn't show up unless you have comprehensive insurance. Many comprehensive coverage plans include windshield coverage, and some states may even require it.
However, there are comprehensive plans that don't include damage to glass, or you might want glass coverage without paying for full comprehensive insurance. What's the solution? Many insurance companies offer a rider specifically for glass damage (sometimes it covers just the windshield, sometimes all the windows in the vehicle).
Now for the $64,000 question: Is paying for glass coverage a good idea? It depends on a few factors. First, of course, is how much your insurer is going to charge you for a glass rider. This will depend on the vehicle, but can range from $100 to several hundred dollars. Next, look at your deductible. This is the amount you pay for repairs out of pocket before your insurance kicks in. If you have a high deductible, chances are the cost of repairing or replacing a damaged windshield won't even meet the deductible, so paying extra for glass coverage is a waste. Finally, consider how likely it is that your windows will be damaged. Lots of driving on gravel roads is usually bad for windows. If you regularly park on the street, your windows might fall victim to a neighborhood street hockey game or a car-breaking thief.
Keep in mind that windshields can be repaired pretty easily these days as long as the damage isn't too severe. Most chips and small cracks can be fixed for a fraction of the cost of replacement -- and a bump in the road can turn a tiny chip into a huge crack. Replacement is even easier, too, with mobile windshield replacement trucks that will come right to your driveway and swap in a brand new windshield in no time.
With all of these factors in mind, in most cases it is not worth the extra money to pay for glass coverage.