More inner cover ideas... continued.
Here are the dimensions of the 'spring' and 'winter' inner cover. There is a piece of 1/8th's discarded paneling cut on my table saw to match the size of a typical 8 frame super.
Along with this, I use a small 1 ½ inch ventilation hole that is screened that permits air flow in the hive when we get rather hot in the summertime. Hard to imagine now with our late winter snow and all! I use screened bottom boards a method of mite mitigation but the real benefit might be the reduction of excess moisture in hives. I leave a small piece of wood there to block this off during the colder times of the year.
These pictures show the adjustable upper entrance. A simple screw holds it in place and allows you to quick close or open – depending on the weather or time of year.