If you turn to page 116 of Seeley's book The Lives of Bees, you'll find a reference to Derek Mitchell a PhD Candidate in Mechanical Engineering at the University of Leeds. With web-based searching, I discovered Derek's 2017 article in the American Bee Journal (Vol. 157 No. 8) Honey Bee Engineering: Top Ventilation And Top Entrances. The article illustrates that adding top ventilation significantly reduces humidity and the depth of the heat pool when compared to an uninsulated hive. Why? Warmer air is more buoyant and flows faster through the top vent.
Providing hive insulation in winter reduces bee-generated heat loss and this increases the temperature of the heat pool found at the top of the hive - see the image from Derek's article. I'm using the word heat pool as temperatures measured relative to the top of the hive -- I recognize, pool is commonly used with liquids that fill upwards from the bottom of containers. I currently use insulated hive wraps in winter and plan to close my top vent moving forward.
Derek has simulated the heat flow of a winter bee cluster in a thin-walled wooden hive and compared those results with measurements collected by other researchers. I plan to discuss this article in an upcoming blog post.
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