I had several beekeepers interested in My inner cover design so
here it is.
 
        Take a standard inner cover with a 3/8" lip around the outside edge
and a hole in the middle. This cover should have slot type opening in the
front lip.
Place the cover on a table so that the slot is in the up position. Take a
3/8" thick piece of wood about an inch wide . Place it across the width of
the inner cover.  Leave a 1" gap between the end of the stick and the
outside lip on each side. Place the stick back from the front Approx 1" to
1 1/2"and permenetly fasten it. Next place a piece of 3/8" plywood over the
entire cover,and seal the edges well so that no air can leak out from the
edges. This creates a 3/8" layer of air between the part of the cover which
is exposed to the inside of the hive and the part of the cover exposed to
the out side of the hive.The bees will get in the openings and controll the
airflow.
 
        How I use the frostfree inner cover here in Alaska.
 
1       I cut a 3"round hole in the upper surface offset from the bottom
hole as a feeder hole so I can feed in february when they start raising
brood.
2       Place the cover on top of the hive with a deep super on top of that
filled with insulation and exterior cover on top.
3       Duct tape all joints to keep the wind from blowing through or wrap
with insulation. Several of our beekeepers use styrofoam board insulation
and build a hive size box with upper and lower entances. Long ago some one
told me the bees would chew the styrofoam but I have not see that happen.
 
4        Reduce the lower entrance to a size slightly smaller than the
upper entrance ,this lets the bees controll the air flow better.
 
5       When the bees start to raise brood again in february They need to
raise the humidity of the hive for the brood.Put a feed can in the
insulated super on top over the hole. Thin syrup, Mix more water than
sugar.
 
6       I use a coffee can for a feeder and use a paper clip to poke a lot
of holes in the plastic lid, be sure to tape completey around the lid seal
to prevent air leaks or the feed will run out. Also be sure to fill the can
well so it will build its vacuum quickly.
 
                                        Well there you are best luck
                                        Jerry Fries