For cold climates it is advantageous to use an inner cover which
incorporates an inch of styrofoam between two layers of plywood or
tempered masonite. It has a 3/16 by 3/4 inch rim top and bottom with a gap
on one side to use as an upper entrance during the winter. I keep these on
year round and do not use burlap ( why do people use burlap anyway? ).
There is never any trouble getting them off.
 
The tempered masonite is a hardboard material which has been treated to be
water resistant and seems to stand up well inside beehives.
 
If you don't use the rim, the bees fasten the cover pretty firmly to the
top bars and there is some chance of delaminating the plywood when the
cover is pried off. Luan plywood in my experience is not waterproof and
delaminates by itself in wet conditions. We use exterior grade fir plywood
which is bonded with a completely waterproof glue.
 
 
 
 
Donald Aitken
11710-129 Street
Edmonton Alberta Canada
T5M 0Y7