What wombats said. Looking at the measurements, looks like 12-13 cubic feet. I ran a half pound in my airtight but opened often 2cubic foot box and it struggled in the winter. Upgraded to a full pound and was fine. Id imagine 1/3-1/2 lb per cubic feet would be ideal. Maybe can get by with less if the box is full and not opened much.
Or run an active unit and half as many beads.
danmdevries wrote: