I'm no meteorologist nor physicist, but have been looking into relative humidity, dew points, vapor pressure, and the evaporation and sublimation of water (ice directly to vapor). I've also reviewed the recorded temperature isotherms in wintering hives (Owens, Szabo). The bees appear to have mixed feelings about upper entrances, and may move away from them, or perhaps block them with their bodies. Owens felt that the main advantage of an upper entrance was to allow cleansing flights. As far as condensation being a problem, I suspect that one could predict it from maps of dew points and average winter temperatures. Please refer to the attached map. The combs around and below the cluster rarely drop as low as the outside ambient temperature, and may get cold enough for the water vapor escaping from the cluster to freeze. Since the temperature of those combs is above that of the outside air, the water (whether frozen or not) will have a greater vapor pressure than the local atmosphere, and the water will tend to evaporate. In areas with very low dew points, the condensed ice may evaporate out completely, and the colony may need to conserve water to prevent desiccation. But as the ambient temperature rises above freezing, any moisture condensing on the combs would be in the liquid state, and its evaporation rate would be relative to how much the cluster was warming the combs outside the cluster. It would also depend upon the dew point--the temp at which water vapor would no longer evaporate. Once the temperature of the outer combs exceeds that of the insulating shell of bees--around 50F--any water would be expected to evaporate, at a rate relative to the relative humidity (which can be calculated from temperature and dew point). I'm guessing that those who report moisture and mold problems lie in areas in which the dew point is close to the temperatures of the outside combs, which are often in the 20-40F range. Take a look at the map above (keeping in mind that actual daily dew points are very much dependent upon the day-to-day weather conditions, not the average). So my question to the List is whether those who are reporting moisture problems tend to fall into one of the colored dew point gradients in the map above. Please let me know whether or not you observe moisture/mold issues in uninsulated hives, and the dew point gradient your hives are in. Please email [log in to unmask] In the subject line please write Y or N for moisture problems, and the dew point isotherm from the map above (e.g., 20-30). Example: Y 20-30. Thanks in advance. -- Randy Oliver Grass Valley, CA www.ScientificBeekeeping.com *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html