[Z-man]

Fire codes for garage-to-house entry doors vary from town to town. My town requires a 20 minute burn-through door. Biggest difference between a 20 minute burn-through rate and higher rates (45, 60, 90 minute rates) is that the frame of the higher numbered doors are metal, not wood. IIRC, all fire rated doors are metal, or have a metal outside layer.

What is interesting is this: from what I heard, there is no testing/certification done on 20 minute burn-through doors - they simply put a sticker on it. The testing starts are the next level of doors. So a 20 minute burn-through door is essentially a steel door in a wood frame, plus a pair of self-closing hinges.

Best bet for the OP: check with your town for what types of doors they require, and see if they will allow a door with a window in it, if that is your desire. You may not care much about this now, but if you sell your home, you may not get a CO (Cert. of occupancy) if they fail you on the door.

As always, YMMV,
-Z-man.