This is great, but I it could be even better if it included the UKU extension box too, since a lot of buyers will be needing help with that and the print instructions are a bit overly simplistic.
From an energy consumption point of view, yes, a glass door is not optimal. Glass door though can be an aesthetic thing. Also it gives some level of safety, as you can see through it and be aware if people on the other side of the door are OK. If the sauna has well-designed ventilation, then the air gap is not needed, but most of the saunas lack ventilation. As they say, you can't have too much fresh air in the sauna. Without enough fresh air, you will get a dizzy head and the sauna session is not as pleasant as it could be. We wrote a blog post about ventilation: huum.eu/blog/guides/ventilation/
