This is my second year with SBB and I wasn't certain whether to leave them open or closed either. I contacted a semi-commercial beek near me who has several years experience, and for our area, Southeast Missouri, he has much better luck closing them off in the winter. So I closed mine off. Several other places I've read suggest to close them off, because of earlier brood rearing in the spring, and cutting off drafts.
If you have an upper entrance/opening, that helps with condensation. So too does the mountain camp method of sugar feeding.
I just have 6 hives, all with SBB's. They all also have reasonable wind barriers. However, having just a few hives, can afford to micromanage. Therefore, I leave them open, even in the coldest of cold. When it gets windy, however, will slide in the bottom to the SBB's. It's usually only for a day or so, until the cold front passes. The reason, is because of what's usually mentioned here and in literature, that the cluster has a harder time in wind than with cold, per se.
Even though my winter is milder than some of you guys', I do slide a board under my SBBs. It does not make the hive completely air tight. There is still plenty of ventilation. As a matter of fact, yesterday since I knew no bees would be flying, I got on my hands and knees to peek in the front entrances. There is enough light coming in thru the SBB, even with the slat, that I can see how many dead bees are on the screen. The light tells me that there is enough ventilation. I also use an inner cover from Rossman that has a notch for airflow up top.
When the mites fall off the host bee during grooming or other activities, the mite falls to the bottom of the hive. A solid bottom board, or closed sbb, allows the mite to hitch a ride on a passing bee. With a sbb that is open, the mite falls thru the screen to the ground and perishes.
I'm in Ontario its been around -10c or 14f for the last two weeks. I put screened bottom boards on about 50 of my hives as a test this winter. I think as long as you don't have cold air blowing into the hive you are o.k. The real killer is moisture and condensation. To prevent this I insulate above the inner cover and have an upper entrance. Todd.
A forum community dedicated to beekeeping, bee owners and enthusiasts. Come join the discussion about breeding, honey production, health, behavior, hives, housing, adopting, care, classifieds, and more!