Re: Screened Botton Boards and a New England Winter
I don't know how Iowa winters compare with New England winters, but the Iowa study with Russian bees and screened bottoms vs solid bottoms had no difference with overwinter success. The screened bottom board colonies did use about 20% more food during the winter. That was equal to one medium frame of honey.
If you don't close the screen off, don't use upper ventilation. A closed inner cover is what is needed with screened bottoms. If the adult population is not very strong, I would close off the screen.
42 + years - 24 colonies - IPM disciple - Naturally Skeptic