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Yes, Hive Insulation Is Good Year-Round – A Deeper Dive

Posted March 21, 2025

Introduction

The honeybee (Apis mellifera) displays advanced regulation of the nest climate, in summer as well as in winter. Thermal homeostasis (thermoregulation) of the colony is especially important for the brood, because honeybee larvae and pupae are extremely stenothermic (surviving only within a narrow temperature range). A brood nest temperature of 93–95 °F/32-36 °C guarantees a high and constant development speed. Accordingly, the accuracy of thermoregulation is high in the presence of brood, and much more variable and generally lower in colonies without brood. While eggs and larvae (in open brood cells) can tolerate also somewhat lower temperatures for some time, the pupae (in sealed brood cells) are very sensitive to cooling. If pupae are exposed to temperatures lower than 93 °F/32 °C for too long there is a high incidence of malformations of wings, legs and abdomen. Adults may also suffer from behavioral and neural insufficiencies especially if temperatures are too low but also if they are too high during development. Since the brood lacks regulatory ability and does not produce enough heat by itself for proper development, achievement of thermal constancy in a variable environment has to be accomplished by the worker bees. Warming behavior is triggered by chemical and tactile stimuli of the brood, and sealed cells were reported to be more attractive than open ones. The worldwide distribution of honeybees and their fast propagation to new areas rests on their ability to keep up optimal conditions in their brood nest both in the cold and in the heat. Honeybee colonies behave like ‘superorganisms’ where individuals work together to promote reproduction of the colony. Social cooperation has developed strongly in thermal homeostasis, which guarantees a fast and constant development of the brood.

Heat

The measurement of body temperature together with bee density and in-hive microclimate shows that behaviors for hive heating or cooling are strongly interlaced and differ in their start values. When environmental temperature changes, heat production is adjusted both by regulation of bee density due to migration activity and by the degree of endothermy (heat generated by the bee). Overheating of the brood is prevented by cooling with water droplets and increased fanning, which start already at moderate temperatures where heat production and bee density are still at an increased level. This interlaced change and onset of different thermoregulatory behaviors guarantees a graded adaptation of individual behavior to stabilize the temperature of the brood.

Clustering

All substances can create a temperature difference. The use of the word ‘insulation’, in connection with clusters, means more than that. It implies, in this case an unwarranted, positive value judgement about the substance or configuration and has, with its repetition, influenced interactions with honeybees, encouraging practices of using thin-walled wooden hives and the North American refrigeration of honeybee colonies. But, any reasonable interpretation of the word ‘insulation’, the clustering process results in its decrease and that a cluster is an increase in conduction, mitigated by collapsing the colony domain. A transition from a state where the honeybees can suppress internal convection within the nest, into a state of high internal convection and conduction, resulting in increased individual honeybee stress. This is opposed to the conventional view that the cluster is a benign thermal improvement on the pre-cluster state. This view does not match the recent advances in research, and enables an avoidable increase in honeybee stress, (i.e. refrigeration and use of hives not significantly different in performance from thin metal), when they are facing unavoidable increases in stress from pests, disease and climate change.

Ventilation

Apis mellifera colonized northern Europe about 1 million years ago and later, with our help, North America, by making its nests in tree hollows. These hollows are on average very highly insulating compared to our thin-walled hives. Thus, developing a preference for bottom entrances would have given them a definite survival advantage in making use of the insulation advantages of thick-walled tree cavity without incurring the disadvantages. Beekeepers have been discussing the subject of the top ventilation of hives for over a hundred years. This interest peaked in the 1940’s and it was taken to be accepted practice, especially in the United States, to have top entrances or vents open in winter. The 1975 to the 2015 editions of “The Hive and the Honey Bee” says that “Heat is not lost through the upper entrance” citing Edwin Anderson’s 1943 experiments. Yet we learn that honey bees seek nests with lower entrances when they can find them. For such a behavior to develop honey bees must surely have found some advantage.

Edwin Anderson’s experiments used hives with only bottom entrances and both top and bottom entrances , he placed a 15Watt electric bulb in the bottom and a single thermometer. He reported that “The temperature in this hive with the top entrance remained about the same as the one with a bottom entrance only”. Did Anderson make a mistake? Did the beekeeping community draw a wrong conclusion from his results? Are honey bees not concerned with heat when they choose a lower entrance? This problem of a heat source in a box with a hole at the bottom and one at the top has been well studied by engineers and they have performed experiments almost identical to Anderson’s. The engineers using sophisticated instrumentation, described what happens in detail and have derived mathematical models to predict temperature and heat transfer. Their studies show, that by relying on a single thermometer, it was impossible for Anderson to pick apart what is a very complex system of fluid mechanics and heat transfer. A system that depends, even at simplest level, on the size and shape of the top vent and bottom entrance, the way the heat moves through the walls and roof, and how air moves and mixes inside.

Although the statement that “no heat is lost through top vents” is technically incorrect, in uninsulated hives that lose so much heat through the roof and walls that the heat pool under the lid is cool, the addition of vents may not make much difference. But in a hive that loses very little heat through the lid because of insulation, the addition of top vents is very significant and can be detrimental. The consequence for the honeybees in the winter is that any thermal advantage of installing insulation can be negated and perhaps even reversed by the addition of a top vent. This high velocity flow through the top vent will move the previously slow or stagnant air (i.e. entrainment) and remove moisture from the internal structures such as larvae (forced evaporation). This not only dries parts of the hive it also cools the hive as evaporation of water needs energy (evaporative cooling). The honey bees now have the added problem of dehydration. Without the top vent, the air would be hot and humid, good for bees. With the top vent, the lower parts of the hive are cold and top parts hot and very low humidity, not good for bees. Not surprisingly, researchers in the performance of colonies in insulated hives with added top vents have been rewarded with poor or inconclusive results for their labors. In both cases of insulated and uninsulated hives the addition of top vents does not change the temperature at the top but changes how much of the volume of the hive is warmed.

Trees vs Man-Made

Honey bees preferentially occupy thick-walled tall narrow tree cavities and attach their combs directly to the nest wall, leaving periodic gaps. However, academic research and beekeeping are conducted in squat, thin-walled man-made hives, with a continuous gap between the combs and the walls and roof. Studies have shown that the heat transfer regimes in complete nests in trees and thin-walled man-made hives are fundamentally different. For instance, including bee space above combs such as between boxes of frames increases heat loss by up to ∼70%. This means that hives, compared to tree nests, require at least 150% the density of honey bees to arrest convection across the brood area. Tree cavities have a larger vertical freedom, a greater thermal resistance and can make dense clustering redundant. With the thermal environment being critical to honeybees, the magnitude and scope of these differences suggest that some hive based behavioral research needs extra validation to be considered non-anthropogenic (not caused by beekeepers), and some bee keeping practices are sub-optimal.

This experimental research, using various hives and thermal models of trees, has found that the heat transfer rate is approximately four to seven times greater in the hives in common use, compared to a typical tree enclosure in winter configuration. This gives a ratio of colony mass to lumped enclosure thermal conductance (MCR) of less than 0.8 kgW−1 K for wooden hives and greater than 5 kgW−1 K for tree enclosures. This result for tree enclosures implies higher levels of humidity in the nest, increased survival of smaller colonies and lower Varroa destructor breeding success. Many honeybee behaviors previously thought to be intrinsic may only be a coping mechanism for human intervention; for example, at an MCR of above 2 kgW−1 K, clustering in a tree enclosure may be an optional, rare, heat conservation behavior for established colonies, rather than the compulsory, frequent, life-saving behavior that is in the hives in common use. The implied improved survival in hives with thermal properties of tree nests may help to solve some of the problems honeybees are currently facing in apiculture.

Wood vs Polyurethane Hives

The vast majority of modern managed honeybee operations in the USA keep bees in frame-movable hives which slightly varies in their design between models in other countries. Up until today, the most popular and widely used hive by professional and migratory beekeepers remains the 10-frame Langstroth hive. Since its establishment in 1852, the design of the Langstroth movable frame hive has not fundamentally changed. Nevertheless, prior to the establishment of modern hives, honey bees were raised and sheltered in different types of boxes and hives which varied in shape, size, material used, and honeycomb accessibility.

The main objective of a hive should be to shelter bees and provide them with a cavity which they can efficiently thermoregulate to maintain their brood nest within an optimal and narrow range of temperature (93–95 °F /34–35 °C); critical for brood development. Langstroth hives are made of soft lumber wood, and its wall thickness is approximately 3/4 inch which provides relatively low insulation value for the same thickness compared to other new commercial materials such as polyurethane, fiberglass, and rock wool blown. The insulation value (R-value) is the measurement of a material’s capacity to resist heat flow from one side to the other; also called the effectiveness of insulation for a given material. Therefore, the hive’s material and its R-value are critical as bees have to adjust and maintain both inner hive temperature and humidity at optimal levels in order to produce healthy brood and survive the winter season. Non optimal temperature or fluctuation in the brood nest could lead to brood damage, adult bee deformation and decline in cognition abilities and development of diseases. Based on the wall thickness and type of wood used in the Langstroth hive, its insulation value (R) ranges between (1.2–1.3) while other newer material such as polyurethane provides much higher value (6.2) in equivalent thicknesses.

Testing showed that polyurethane hives maintained a significantly (P < 0.001) higher overall temperature (10.20 ± 0.04 °C) than wooden hives (9.73 ± 0.05 °C) with a significantly more optimal relative humidity (52.05%) compared to the wooden hives (62.50%). Inner temperature patterns of the wooden hives exhibited pronounced oscillations compared to the polyurethane hives. Both hive groups showed significant differences (P < 0.001) in temperature insulation between day and night cycles. However, the polyurethane hives seem to provide better stability in humidity between days and nights compared to Langstroth wooden hives.

Besides the insulation factor of the hive material, a recent study showed that honey harvest or the process of removing honeycombs (especially above the colony) from the hives would lead to loss of considerable thermal mass in the hive reducing the internal thermal stability. Such thermal loss will require significant energy to be replaced as well as the reheating of the extracted honeycombs when placed back above the colony. During the winter time, clustering and increase in the metabolic rate are the main remedies to counter cold temperature. This behavior requires significant energy obtained via higher honey consumption by bees. Thus, better hive insulation can play a crucial role to minimize the amount of energy required to thermoregulate the hive cavity and subsequently, decrease honey consumption which, if depleted, can lead to colony winter starvation and death.

Hives and Buildings

Apis mellifera – Apis, which is Latin for ‘bee’, and mellifera, which is Latin for ‘honey-bearing’ – refers to Western or European honey bees. Research shows that regardless of the ambient temperature, the in-hive microclimate of a beehive at the central brood area must be kept at the average optimum temperature of 95 °F /35 °C for the colony to survive. Therefore, to survive both cold winters and hot summers, Apis mellifera will employ several heating and cooling strategies to thermoregulate their hives at the optimum temperature. Just like beehives, our buildings are designed with an envelope that is frequently viewed as the barrier that protects the internal occupied space from the impact of the external environment. We also employ similar methodologies to thermoregulate our buildings to reduce the heating and cooling load for less energy consumption while at the same time providing thermal comfort to the occupants. Many similarities can be seen between the honey bees’ hive and our buildings’ thermal management system. However, we can still learn from the thermoregulation management demonstrated by the honey bees, for example, the fact that the temperature stability of the beehive has been very consistent and well maintained regardless of the ambient climate. This is owing to the decentralized and collective decision-making employed by a honey bee colony. The worker bees in a colony are not being ‘allocated’ tasks in any way. However, any form of disturbance or changes detected in the hive’s environment are individually assessed by each of the worker bees and then immediately passed to the other bees through their special communication technique, ‘chemical communication’, via the pheromones secreted by the bees and their special dance language, known as waggle dance or wag-tail dance. We can compare this to the heating and cooling control system of a house with tens or hundreds of installed integrated thermostats. A heating or cooling system in a house mainly has a centralized control that has a slow response and feedback and is highly variable but with less energy and capital cost consumption. Nevertheless, human beings have indeed employed several decentralized control strategies in buildings, which include the use of a motion sensor lighting system to reduce lighting loads in non-used space.

Hives and Honey

A study was completed investigating the effects of man-made hives built from different materials and how these may influence colony growth. Ten each of three hive types were selected, wooden, polystyrene and composite insulated hives. Factors of adult bee numbers, brood development, nectar flow period weight gain, bee flight activity, aggression response, and honey yield were selected markers of hive development. Statistically, each hive type produced significant variation (p < .05). The greatest overall productivity across all factors was for insulated hives made of composite material, with honey production approximately 35% times that of wood, 14% times that of polystyrene and in terms of the development of honeybee colonies, the average of other hives is 10.2 times.

Since thermal insulation of hives from pine boards is not sufficient, the average minimum temperature is lower than in other hives (polystyrene, insulated) types. The insulated and polystyrene hives were significantly influential in preventing the internal temperature from falling too much, but the wooden hives were unable to provide this (p < .05). When the maximum temperature in the hive is examined, the highest value is in the wooden hive, followed by an insulated hive and polystyrene hive. The polystyrene hive had the highest maximum-humidity value because it couldn’t provide good ventilation, followed by the insulated hive and wooden hive. Hive types were effective in terms of maximum-humidity (p < .05). The highest average minimum-humidity value was measured from the polystyrene hive and the lowest value was measured from the wooden hive.

Hives constructed of pine boards are robust and natural, but their thermal insulation is not very good. In addition, since wooden hives are heavy, it is often difficult to lift or carry. Some migrant beekeepers may prefer polystyrene hive because of their lightweight, but these hives can be easily damaged in the apiary, and they have poor ventilation characteristics. Mice easily gnaw polystyrene hives in the warehouse. Sunlight does more damage to polystyrene hives than other hives. As a result, insulated hives from composite materials such as plywood with insulation in the walls are one of the most suitable types of beehive in terms of beekeeping due to their durability, lightness, heat insulation and the naturalness of the surfaces in which bees come into contact.

Varroa and Humidity

It is highly likely that honeybees, in temperate climates and in their natural home, with much smaller thermal conductance and entrance, can achieve higher humidity’s more easily and more frequently than in man-made hives. As a consequence, it is possible that Varroa destructor, a parasite implicated in the spread of pathogenic viruses and colony collapse, which loses fertility at absolute humidity’s of 4.3 kPa (approx. 30 gm⁻³) and above, is impacted by the more frequent occurrence of higher humidity’s in these low conductance, small entrance nests.

The thermal conductance of the nest and the dimensions of the entrance have a major impact on nest humidity. This makes high humidity a much more likely and frequent occurrence in tree nests and the low humidity found in man-made nests a likely stressor. Low humidity’s observed in some hives may be a direct result of their construction and thermal conductance. Top vents can also tie inside to outside humidity, which even in subtropical climates is substantially below the ideal for larval growth and the reduction of varroa fertility. Therefore, they may increase the levels of honeybee stress and the likelihood of varroa infestation.

Conclusion

Insulation changes internal hive conditions, maintains a lower daily temperature range, a lower humidity, and a lower daily range of humidity. This internal environmental stability was linked to increased early-season honey storage rate, lower Varroa infestation and faster comb building, in comparison to uninsulated hives. Insulated colonies were also found to have an increased ability to take down and convert supplemental syrup-feed in autumn. This argues that insulated hives allow improved effectiveness and efficiency of thermoregulation and imply that improvements to colony health and productivity can follow.

Insulated hives allow colonies a greater control over their environment and support the reduction in energy demanded by key thermally driven colony activities, in turn leading to minor improvements in colony health and productivity. Insulation also led to a consistently altered spatial distribution of brood. However, this wider distribution within the brood-nest space appeared to be an opportunity exploited by colonies as soon as internal conditions allowed so it is likely to be associated with some efficiency perceived by the colonies. Insulation may also help to reduce Varroa infestation levels. Although there is much uncertainty around the mechanism through which this is achieved, hive insulation has potential to assist in the battle against Varroa when used alongside other mite management practices. Apiary layouts designed to create favorable microclimates may deliver similar benefits of equal or greater magnitude, as such any beekeeper considering investing time and money in insulated hives should also consider and compare improvements to apiary micro-climate.

Referenced Materials

Understanding Your Local Swarming Process

Winter Bees and Their Environment

Epigenetics: Honey Bee’s Gene Response

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