A sauna window is the single change that most alters how a cabin feels: a dark box becomes a room with a view, and a small back yard cabin stops feeling like a cupboard. It also costs heat, costs money and has to be the right glass, and there is a sensible amount that most cabins land on.
It has to be tempered
Any glass in a sauna is tempered safety glass, typically around eight millimetres, which tolerates the thermal cycling and breaks into blunt fragments rather than shards. Double glazed units are used in cold climates and need to be rated for the temperature, because a standard sealed unit can fail at sauna temperatures over time.
What it costs in heat
Glass insulates far worse than an insulated timber wall, so every square foot of window is heat leaving. In practice that means a slightly larger heater or a longer heat-up, and it is why makers size heaters against cabin volume with an upward adjustment for glass area. A panoramic wall is a real specification change, not a finish option.
Condensation and the view
A cold single pane fogs from the inside almost immediately, so the view you paid for disappears five minutes into the session. Double glazing rated for the heat largely solves it. So does accepting that the window is for light and for the room feeling open rather than for watching the yard throughout.
Where to put it
Low enough to see out from the bench rather than at standing height, on the wall you actually want to look at, and away from the heater's clearance zone. Many cabins put the glass in the door plus one end panel, which gives most of the benefit for much less heat loss than a full wall.
Questions people ask about sauna window
What glass does a sauna window need?
Tempered safety glass, and if double glazed, a unit rated for sauna temperatures. A standard sealed unit can fail over time.
Does a window make the sauna colder?
It increases heat loss, so size the heater upward for glass area. A panoramic wall is a specification change, not a finish choice.
Why does the window fog up?
A cold single pane condenses on the inside within minutes. Double glazing rated for the heat is what keeps a view.