Here is an article that might be of interest to you. https://www.beeculture.com/winter-management/ This article discusses the various types of insulation and ventilation.
That is the most thoroughly and clearly-explained article about winter ventilation and insulation I've ever read. I was aware of most of it already, but the precise explanations of how it all ties together, insulation with ventilation, was insightful.
It's interesting to see how different beekeepers in different areas take different approaches to wintering their bees.
When I started, all I did was wrap my hives in roofing felt (or tar paper), place a piece of hard insulation over the inner cover and reduce the bottom entrance. That basic method seems to work for many people in cold climates who don't experience extreme temperature and humidity fluctuations in their local climate. It stopped working for me after moving my hives to a more damp fog-drenched climate. That's when I began experimenting with ventilation aids: simple ventilation rims over the inner cover in the summer and winter; moisture quilts / quilt boxes over the inner cover; wrapping and no wrapping; reduced entrances and wide open entrances; etc. The moisture quilts had the most dramatic effect on my hives. Just about every hint of moisture was wicked way from my hives. They were almost
too dry at times. The heat loss in that set up didn't seem too bad.
I know people in my area who have used "Bee Cozies" to wrap their hives. Their colonies come out strong in the spring, but are often bone-dry of honey stores too, requiring late-winter sugar feeding and lots of syrup in the spring so they don't starve. I also know people who only put some kind dark wrap on their hives (roofing felt, black tarp, anything dark) and provide only top ventilation through what is essentially a ventilation rim under a large top cover that provides some dead-air space. In that set up, there is constant ventilation and loss of heat through the inner cover hole. Yet, colonies is these hive (called the D.E. Hive) seem to do well in my local climate; it's a popular hive.
What I've shown in the photo I posted is basically the D.E. Hive set-up but with insulation over the inner cover. But now after reading the article you link to, I kind of get the impression that that insulation might not be doing a whole lot. But it also seems that the effect of top insulation on
any hive with a top-notched inner cover entrance is greatly reduced by the exposure to cold air provided by the upper entrance. I need to read that part of the article more carefully. I may have misinterpreted that part.
I know wrapping is popular, but I'm very close to being completely done with it. My hives are painted black (summers aren't very warm where I live), and except for the hives in wide open areas, they're not wrapped and don't seem to suffer from not being wrapped. But again, my local climate is fairly mild throughout the winter (most of the time). The biggest challenges in my local climate are the wind and precipitation (often blown into my hives at 90 degree angles -- good times). The turning point for my was upper ventilation provided through a ventilation rim over the inner cover -- in both summer and winter (with wood chips to absorb condensation in the winter, basically a moisture quilt).
I've talked to many beekeepers about the necessity of reducing winter entrances, namely because it reduces the cold air hitting the cluster when it's low in the hive. I noticed that most entrance reducers reduced the entrance but the kept the entrance in the middle of the bottom entrance -- right where the cluster often hangs out. So last winter I began reducing my bottom entrances but leaving the sides opened just a little so that airflow would occur on the edges (not the middle) where the cluster wouldn't be bothered by it. That seemed to work out okay, but there was more moisture build-up in the hives too. This winter I've gone with completely open bottom entrances on most of my hives -- which I've done before with no issues -- and the bees in those hives are doing great. Despite the wide open bottom entrances, the clusters stayed low in their hives much longer than the hives with reduced entrances. The cold air blowing in through the wide-open entrances doesn't seem to bother them at all. And I know many beekeepers who swear by wide-open entrance in the winter, claiming it keeps their hives well-ventilated and dry.
So there are many ways to skin this cat, but the evidence-based article you linked to seems like an excellent reference for thinking through my over-wintering strategies. Thanks.
