patio doors

I have Alliance patio doors on my home of 5 years. Last saturday while we were out one door (the slider) cracked into a million pieces on the inside glass. It was in perfect condition when we left and no one was home. Now the company says it covers the door on the warrenty but not the glass---HUH? The door is 90% glass. What happened? This door is 5yrs. old and leads to an enclosed porch--totally protected.

How old is the door?

Usually (at least on windows) the glass warranty is the more long term warranty as compared to the frame sections.

There aren't too many warranties on patio door glass in most cases though so keep that in mind.

+1, many if not most companies do not have breakage warranties. Unless you have evidence otherwise, the manufacturer would assume that something hit it, as that would be the most common explanation by far.

With tempered glass when the breakage cause is not known it is sometimes refered to as spontanous breakage, there really is no spontanous breakage it is that the sorce has not been ID.
Is there grass on a lawn near the door, most of the tempered breakage I see is either a mower or whacker thrown stone, it sometimes creates a vent in the glass that may fully break with a secondary stress.