This grill is designed to cover the hole that is left on the exterior wall of the sauna when the 4" x 6" through hole is cut. These can be painted or left natural. They are handmade of clear western red cedar and allow air to easily flow in and out. Exterior dimensions are 6 5/8" x 8 5/8".
All sauna heater manufactures specify a passive venting system composed of an intake vent below the sauna heater and an exit vent located up near the top of the room. Ideally, these vents are connected to same adjoining air space, preferably not the outdoors. This venting system provides cool make up air to the sauna heater so that the thermostat sensor does not prematurely overheat and shut down the sauna heater. This venting system also provides some convective flow which mixes the air in the sauna providing a more uniform temperature from top to bottom. It also provides fresh air flow and enables you let the room breath after each use. This provides more complete drying of the sauna lumber which promotes longevity of the sauna room itself.
When framing the sauna these vents need to built into the walls as shown below.