Interesting device. I think of a SBB as a device for letting debris and mites out of the hive
not a ventilation device.
Yes Ace, a perspective generated from continually owning "dirty" BBs which is
a direct outcome of either low numbers than the box volume requires or bees
not inclined towards hygiene. One can be fixed, the other culled.
Regardless of how you view SBBs the fact there is a bloody great hole bees cannot
control is "ventilation".
Some apply a closure below the screen which in turn generates a rubbish/trash
bin/can bees cannot access and so creates yet another problem for bees. Sure
regular removal to clean off has merits _provided_ it is done regularly like every
other day where the colony is active and not viewed from the stoop/patio (beer
in hand) with a "must pull those corflutes, shortly" approach to beekeeping.
Cheers.
Bill