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?
Thanks
Best Answer
Small-duct systems normally use a fan that provides high-pressure, not high-volume. Air will not move through those small holes without a fan unless there is a pressure differential, or a strong vertical convection caused by heat.
Use firring strips to build out the wall, and to get a better duct size and design. Then add an exhaust fan where the warm air exits the structure.