Last summer at our Maryland State Beekeepers Assoc meeting, one of our
members discussed ventilation with Dr. Ed Southwick.  The local beekeeper,
Dan Folk, said he has progressively increased the ventilation space in his
inner cover by putting holes in the coners and covering them with screen.
 Each year he increased the size of the holes until he felt the ventilation
was adequate.  Moisture was a big problem and the increased venitlation
prevented the moisture buildup.  He said propolis was not a problem.
 
Sadly, both passed away two month later.
 
David Morris
Laurel, MD