He did a great job with the materials that he used! I would recommend using plexiglass instead of glass because glass blocks a lot of the IR light. The IR light is your main source of heating and he would have gotten a few more hours of usable heat and higher temperatures if he had used plexiglass. This passive heater is a good example of what can be done for very little time and money.
Improvements (at added expense) would be better insulation, double pane plexiglass front (plexiglass is transparent to IR but will block some of the UV (it will eventually turn the plastic a cloudy white) but will never block the IR - even when cloudy. Using "pink board" insulation rather than the OSB/particle board will lose less heat and it is easier to cut and glue together as well as being a lot lighter. Using a "duct" made of the pink board will also allow you to vent the hot air directly into the house while keeping the cold air out.
Still, a very good job and an excellent example of thinking "outside the box".