I need to vent a sauna room (~200F) with an inlet duct that will open below the heater and an outlet that will open near the ceiling at the opposite side of the room. The ducts will be small (2"). Drilling through the studs I'd like to make the holes small (.75") to preserve structural integrity. The only air pressure here will be that provided by the temperature of the air itself, from the outside (30-90F), to the inside (~200F).
Are there any downsides to the small bottlenecks through which the air is going to flow? I'd think the air would just accelerate through the bottleneck and other than that everything else would be the same. Do I need to drill bigger holes?