like perry said, i would be concerned about absorbing all the moisture. i think sometimes we over think things when it comes to our bees. for years i did nothing except leave an entrance reducer on and a top entrance cut out of the inner cover, with nothing above. i moved to insulation on top. i have used straw/hay in a super above the hive. this does work well. i did try homosote, if you ask me this can be deadly to bees. it does absorb moisture, a lot of moisture, but soaks it all in, and when a thaw comes, rains back down on the bees.....my HO.
another experienced member here, robo, doesn't use an upper entrance because of the heat loss. we all have different methods and different situations, we do what we think is best and what works for us. i always keep an open mind though on what works for others similar to my climate.
the only way to find out is to try it. but not just one year, several years to see how it works, and share your experience with it.
