I've got a KTBH with a screened bottom. And whenever I show up, half the bees are underneath in a ball.
Not sure what to do. ONce in a while they build a comb under there.
Close off the screened bottom board. :)
Leave it closed for about a month so that all the new replacement foragers, as well as the current work force, get used to entering the hive via the entrance. Then it should be okay to reopen the SBB.