You don’t have easy, quick access to your attic? That’s bad; very bad.
You need access to your attic—if for no other reason than to inspect the inside of the roof for leaks. And, I’m not talking about removing a vent. You need a PERMANENT way to easily get up there. Either an attic staircase or a hole (I recommend spending the extra money and putting in a pull-down staircase).
You need to add insulation to your attic floor. This will pay for itself over time as it will (1) reduce your air conditioning bills, and (2) more importantly reduce your heating bills.
Thanks for the responses so far.
We can access the attic, but this space is under another, lowered section of the house. The house has a main part and two wings off the side. One wing was completely finished off, the other has a garage on the first floor and had an unfinished storage space above. We finished off that storage space into a room. That’s the sauna.
We have an attic over the main portion of the house, and we have full access to that. We don’t have access to the space above the formerly unfinished wing. There is not enough room to stand in that part— it’s maybe 3 feet high and at a roof angle. The duct goes into the lower roof’s gable, blocking access to that crawlspace.
Also, the heat comes out of the lights when they’re off. It just flows into the room from the light cans.