0. Abstract

This article offers a critical analysis of recent work on thermoregulation in honey bees (Apis mellifera) and the impact of insulation across different climatic and beekeeping contexts. Drawing on biophysical, ecophysiological, and evolutionary research, it shows that the colony has a remarkable capacity for self-regulation, based on collective heat production, the regulation of CO₂ and humidity, and adaptive cooperative behaviour.

Findings from the literature indicate that insulation can provide an advantage in cold regions or for small colonies, but becomes counterproductive when it prevents winter rest or weakens natural selection. The article therefore argues for a contextual and evolutionary approach to winter management: sustainable beekeeping relies on a balance between intervention and trust in the bees’ natural resilience.

1. Introduction – Why the question remains relevant

Insulating hives during winter remains an old and controversial practice, both among beekeepers and in apicultural research. Some studies report a measurable reduction in energy consumption and winter losses in colonies kept in insulated hives (St. Clair et al., 2022; Alburaki & Corona, 2021). Other work, however, emphasizes that honey bees (Apis mellifera) possess remarkably efficient collective thermoregulation mechanisms, making such intervention sometimes unnecessary—and even counterproductive in the long term (Oskin et al., 2022; Seeley, 2019).

This controversy reflects a fundamental tension between two logics: technical compensation for environmental constraints and natural selection shaping lineage resilience. On the one hand, insulation is seen as a rational means to mitigate thermal stress and preserve honey stores; on the other, it may interfere with evolutionary adaptation processes by favouring the survival of colonies that are genetically less tolerant of cold (Neumann & Blacquière, 2017).

Recent research in biophysics and ecophysiology has considerably refined our understanding of the hive’s internal microclimate. Cook et al. (2021) showed that certain beekeeping practices—such as reducing thermal mass by removing frames—can temporarily increase heat losses, requiring additional energy expenditure to restore thermal balance. Oskin et al. (2022) confirm that the temperature at the core of the winter cluster depends primarily on the bees’ density and metabolic activity, far more than on the insulating properties of the hive walls. Along the same lines, Stabentheiner et al. (2021) describe the colony as a homeothermic superorganism capable of actively regulating heat production and dissipation—an ability unique among social insects.

The insulation debate now unfolds in a changing climatic context. Desai & Currie (2016) and DeGrandi-Hoffman et al. (2025) show that milder autumns and shorter winters extend the brood-rearing period, thereby increasing resource consumption and vulnerability to parasites. In parallel, Smoliński et al. (2021) point out that seasonal temperature increases reinforce the proliferation of Varroa destructor, further complicating thermal management of colonies. Insulation may therefore sometimes offer an adaptive advantage in cold regions, while in more temperate climates it may amplify metabolic or parasitic imbalances.

The aim of this article is to examine, based on recent scientific literature, the actual and potential effects of hive insulation on thermoregulation, winter survival, and the evolutionary dynamics of colonies. It will critically evaluate the empirical and theoretical arguments underpinning this practice, in order to determine to what extent it constitutes a help, a neutral factor, or a hindrance for bees across different climatic and beekeeping contexts.

2. The biological basis of thermoregulation

The honey bee colony functions as a superorganism capable of maintaining a remarkably stable internal temperature despite external fluctuations. This thermal homeostasis relies on a complex interaction between individual physiology, cluster density, and the collective regulation of ventilation and humidity (Stabentheiner, Kovac, Mandl & Käfer, 2021). Unlike most insects, adult bees can produce heat through endothermic muscular thermogenesis. In winter, workers cluster into a dense ball whose core temperature ranges from 25 °C to 35 °C depending on the presence of brood, while the periphery can drop to 10 °C. This internal thermal gradient is a key energy-saving mechanism for survival (Seeley, 2019).

Maintaining this microclimate is ensured through collective coordination: bees in the centre actively generate heat via muscular contractions, while those at the periphery regulate heat loss by adjusting cluster density according to local cooling. This rhythmic expansion and contraction ensures an even distribution of heat and prevents the formation of lethal cold zones.

Illustration 2: Maintaining the microclimate is ensured through collective coordination (Oliver, 2016)

When the colony is in a phase of winter rest without brood, bees in the centre remain almost immobile and enter a state of torpor or collective sleep, while those at the periphery intermittently provide heat production. By contrast, when brood is present, thermogenesis concentrates in the cluster core, maintaining a stable temperature around 34 °C. This dynamic shift between production and insulation illustrates the remarkable flexibility of the superorganism, able to adapt its energy strategy to internal and external conditions.

Oskin et al. (2022) showed that thermal stability depends primarily on the density and geometric structure of the cluster rather than on the insulating properties of the hive walls. These observations confirm that the colony self-regulates mainly through internal mechanisms in which spatial configuration plays a decisive role.

Beyond temperature, carbon dioxide (CO₂) concentration and humidity are key parameters of the winter microclimate. Meikle & Weiss (2025) demonstrated that temperature and CO₂ follow circadian cycles even during overwintering, suggesting metabolic modulation aimed at limiting energy expenditure. Newton et al. (2024) showed that CO₂ fluctuations can be used as an indicator of brood activity and the size of the overwintering population. Moderately elevated, yet colony-regulated, levels appear beneficial: they reduce excessive ventilation and maintain humidity favourable to thermoregulation, while also limiting the proliferation of Varroa destructor (Bahreini & Currie, 2015).

From this perspective, the hive acts as a self-regulated bioclimatic chamber. Exchanges of heat, humidity, and gases depend not only on external conditions but above all on collective behaviours and the colony’s internal morphology. Stabentheiner et al. (2021) emphasize that bee thermoregulation is an emergent phenomenon: no single bee controls temperature on its own, yet the group achieves it through multiple adaptive feedbacks. These properties explain the resilience of wild colonies observed by Seeley (2019) in the Arnot Forest: despite the absence of artificial insulation, they maintain thermal stability comparable to that of managed colonies.

In sum, the biological foundations of thermoregulation show that winter survival in bees relies primarily on endogenous mechanisms of collective self-regulation. Human intervention through external insulation can improve thermal comfort only marginally, and only when it complements—rather than substitutes for—the colony’s natural processes.

3. Positive effects of insulation: empirical findings and experimental limitations

Arguments in favour of hive insulation rest mainly on experimental observations showing reduced energy consumption and improved winter survival, especially in regions with harsh climates. St. Clair et al. (2022) conducted a series of trials under controlled conditions in Canada, demonstrating that hives fitted with insulating covers had significantly lower winter mortality and an average 12% reduction in honey consumption. These benefits were particularly marked in small colonies, where thermal mass is insufficient to maintain a stable temperature on its own.

Alburaki & Corona (2021) report similar findings: polyurethane hives, which insulate better than wood, reduce heat loss and lower bees’ metabolic expenditure, with no negative effects observed on brood or colony health. The authors nevertheless highlight the need to assess the environmental impact of such synthetic materials before large-scale adoption. More ecological approaches were proposed by Casado Sanz et al. (2024), who compared several natural insulators (hemp, wool, cork) using a network of digital sensors. Their results show that wool and hemp offer the best compromise between heat retention and moisture permeability, thereby preserving a hygrometric balance favourable to the colony.

Other studies suggest that insulation affects not only thermal balance but also bees’ physiological and behavioural dynamics. Cook et al. (2021) showed that hive colour, composition, and solar exposure significantly alter internal temperatures, which in turn influence activity rhythms and the resumption of egg laying in spring. Adequate insulation can reduce daily thermal amplitudes, stabilizing the internal microclimate and facilitating a more uniform brood restart when external conditions improve. These effects translate into longer-term energy savings, especially following beekeeping interventions that disrupt the hive’s thermal mass.

Desai & Currie (2016), in a large study on winter losses in Canada, found that insulation contributes modestly but positively to colony survival, particularly when external conditions are unstable. Their analysis indicates that autumn population strength remains the main survival factor, but that insulation provides complementary support under thermal stress. These conclusions are consistent with observations by DeGrandi-Hoffman et al. (2025), according to which warmer autumns increase consumption and require adaptation of thermal management, including modifiable insulation.

At the microclimatic level, Meikle, Barg & Weiss (2022) observed that colonies maintain relatively constant temperature and CO₂ regimes even when ventilation conditions change. This suggests that external insulation, when properly calibrated, can enhance this stability by reducing temperature gradients without hindering the colony’s internal regulation.

In sum, the literature supportive of insulation indicates that thermal protection adapted to the climatic context can improve energy efficiency and winter survival. Benefits nevertheless appear dependent on population size, materials used, and local climate: insulation functions as an optimization lever rather than a universal guarantee of performance.

4. Risks and side effects of excessive insulation

While several studies highlight the energetic benefits of insulation, others point to its limitations and potential side effects when it disrupts natural microclimate regulation mechanisms. Mitchell (2023) showed, through a biophysical model of the winter cluster, that excessive insulation can turn the hive into a “heat sink”, i.e., an environment in which the heat produced by bees no longer dissipates properly. This accumulation increases physiological stress, triggers more frequent ventilation, and thus paradoxically raises energy expenditure. Mitchell’s model suggests that part of the outgoing heat flux is necessary to maintain the gradient that regulates airflow and humidity.

Minaud et al. (2024) experimentally confirmed this observation: in colonies with high internal temperatures during winter, spring mortality was significantly higher. Their measurements indicate that the mean temperature at the cluster core is an early indicator of metabolic imbalance; above 35 °C, brood is maintained artificially, prolonging consumption of stores and promoting bee exhaustion. These results reveal a paradox: overly effective insulation can maintain thermally “comfortable” but biologically inappropriate conditions for winter rest.

From a behavioural and evolutionary perspective, Neumann & Blacquière (2017) developed the concept of “Darwinian beekeeping”, according to which overprotection of colonies—through chemical treatments or physical interventions such as insulation—weakens natural selection processes. By allowing the survival of individuals or lineages less resistant to cold and pathogens, such practices could, in the long term, reduce the overall genetic resilience of bee populations.

Indirect effects on the hive’s microenvironment have also been reported. Sonmez Oskay et al. (2025) note that some modern materials—especially polymers and synthetic foams—can release volatile compounds that may alter bees’ chemosensory behaviour or interact with acaricide treatments. Moreover, insulation that overly limits ventilation can promote the accumulation of humidity and CO₂, creating conditions conducive to mould or secondary pathogens. Bahreini & Currie (2015) had already shown that CO₂ levels not regulated by the colony can cause respiratory stress and reduce flight activity at spring onset.

Finally, several studies indicate that over-insulation modifies the natural transition dynamics between rest and activity phases. Meikle & Weiss (2025) observed that circadian cycles of temperature and CO₂, essential to winter metabolic regulation, tend to weaken in overly airtight hives. Yet these oscillations likely contribute to internal synchronization of the superorganism and to chemical communication within the cluster.

Illustration 3: Over-insulation is counterproductive (https://backyardhive.com)

Thus, arguments against insulation do not deny its occasional usefulness but stress the need for a balanced approach. Inappropriate insulation—too thick, non-breathable, or applied uniformly without regard to climatic and biological context—can disrupt self-regulatory processes, increase mortality, and slow the evolutionary adaptation of colonies. Bee thermoregulation is above all a dynamic phenomenon; any external intervention must respect this physiological and behavioural plasticity.

5. A matter of context: climate, physiology, and beekeeping practices

Research findings converge on a nuanced conclusion: the effectiveness and relevance of insulation depend strongly on climatic context, population strength, and hive type. Benefits observed in regions with long, harsh winters do not necessarily translate to more temperate environments. Desai and Currie (2016) showed, in a large Canadian study, that insulation reduces winter losses only when external temperatures remain sustainably below –10 °C. Above this threshold, uninsulated but strong colonies can maintain their internal microclimate without excessive energy expenditure. The determining factor is therefore not insulation per se, but the combination of thermal conditions, group size, and available stores.

Climate change further complicates this equation. DeGrandi-Hoffman et al. (2025) emphasize that the lengthening of brood-rearing periods in autumn, linked to global warming, profoundly alters colonies’ energy needs. Milder winters lead to prolonged brood activity, increasing food consumption and vulnerability to parasites such as Varroa destructor. In this context, overly effective insulation can artificially maintain temperatures favourable to brood rearing and prevent the winter rest needed for worker longevity. Conversely, light insulation that promotes a moderate drop in internal temperature can encourage a physiological transition towards dormancy and limit brood and parasite proliferation (Smoliński et al., 2021).

Newton et al. (2024) add a complementary dimension: continuous measurement of carbon dioxide (CO₂) makes it possible to assess the match between ventilation and metabolic activity. Colonies spontaneously adjust CO₂ and humidity levels according to cluster density and ambient temperature, maintaining an internal bioclimatic balance. Poorly adjusted insulation disrupts this self-regulation, whereas breathable or partial insulation can, on the contrary, stabilize these parameters without constraining them. The use of natural materials such as hemp or wool (Casado Sanz et al., 2024) thus offers an interesting alternative, combining moderate thermal conductivity with hygrometric exchange capacity.

Local beekeeping practices also influence the relevance of insulation. In regions exposed to wind or strong thermal amplitudes, protecting side walls and the roof can reduce fluctuations and internal condensation (Cook et al., 2021). In milder areas, it may be preferable to rely on controlled natural ventilation rather than excessive thermal confinement. Insulation then becomes a tool for contextual micro-management: it should be modulated according to season, exposure, colony strength, and materials.

Thus, hive insulation is neither a universal remedy nor a practice to be categorically rejected. It belongs within an adaptive strategy in which a fine-grained understanding of local climate, bees’ collective behaviour, and seasonal physiology is essential. The goal is not to replace natural thermoregulation, but to support it when external conditions exceed the superorganism’s adjustment capacity. Sustainable beekeeping rests on this contextual approach, grounded in observation, measurement, and flexibility rather than in the uniform application of technical solutions.

6. Long-term evolutionary and beekeeping perspective

Beyond thermal and material considerations, the question of insulation raises the very relationship between the beekeeper and the living system they accompany. From an evolutionary standpoint, colony thermoregulation results from a long process of natural selection that has shaped collective behaviours of remarkable efficiency. For millions of years, bees have survived extreme climatic variations without artificial devices. This resilience relies on a dynamic of continuous adaptation: adjusting cluster size, modulating brood, moving to better insulated cavities, and collectively regulating metabolism according to environmental constraints (Seeley, 2019; Stabentheiner et al., 2021).

From this perspective, human intervention should not substitute for these mechanisms, but accompany them with discernment. As Neumann & Blacquière (2017) remind us, “Darwinian beekeeping” favours the natural selection of adapted lineages rather than technical compensation for weaknesses. Systematic insulation or excessive feeding can, over the long term, reduce selective pressure and foster colonies’ dependence on human assistance. Conversely, genetic diversity, cold tolerance, and self-regulatory capacity are assets that should be preserved—and even strengthened—by limiting corrective interventions to truly necessary cases.

The absolute priority of any beekeeper should remain the health of the bees. That health is rarely achieved through human solutions projected onto the animal world, but through understanding the biological and behavioural specificities of the species. Bees operate neither according to our needs nor according to our rhythms; they embody a model of collective balance and natural regulation that must be observed before one attempts to correct it. Drawing naive parallels with human physiology often leads to unsuitable interventions: the colony does not need artificial comfort, but an environment conducive to its own mode of adaptation.

Illustration 4: A healthy bee population is always the number one priority. (Foto PatoSan, Pixabay.com)

Rapid climate change nevertheless requires rethinking these balances. Milder winters, prolonged autumns, and shorter cold spells disrupt bees’ physiological cycles (DeGrandi-Hoffman et al., 2025). Beekeepers thus face a dual challenge: anticipating the effects of warming while avoiding a break with colonies’ natural adaptation. In this context, insulation can become a tool for ecological transition—not to standardize practices, but to provide measured flexibility in increasingly unstable environments.

In the long term, beekeeping sustainability will be built less through accumulating technical fixes than through a fine understanding of living dynamics. Trusting self-regulation processes, observing microclimate signals, and adjusting interventions case by case form the foundations of an evolutionary and responsible approach. The hive is not an object to be mastered, but an ecosystem to be accompanied: an alliance between scientific knowledge, sensitive observation, and ecological humility.

7. Conclusion – The balance between intervention and trust

The question of hive insulation cannot be settled in absolute terms. It instead illustrates the persistent tension between two complementary logics: technical intervention intended to compensate for immediate environmental constraints, and trust in bees’ natural capacity to self-regulate. Recent work shows that the honey bee colony, as a superorganism, has a sophisticated physiological and behavioural toolkit to maintain thermal, water, and gas balance even under extreme conditions (Stabentheiner et al., 2021; Meikle & Weiss, 2025). This power of self-regulation, shaped by long evolution, is the foundation of beekeeping resilience.

Studies supportive of insulation (St. Clair et al., 2022; Alburaki & Corona, 2021; Casado Sanz et al., 2024) confirm that well-designed thermal protection can reduce energy consumption and winter losses, especially in small colonies or very cold regions. However, Mitchell (2023) and Minaud et al. (2024) remind us that this apparent improvement can backfire when it disrupts natural cycles of rest and ventilation. Excessive insulation can alter the cluster’s physiological balance, increase spring mortality, and slow natural selection for the most resistant lineages (Neumann & Blacquière, 2017).

Recent literature therefore argues for a contextual and evolutionary approach: insulation should not be treated as a universal norm, but as a modifiable tool depending on climate, population strength, hive type, and beekeeping goals. In cold climates, partial and breathable insulation can support thermoregulation without constraining it. In temperate zones, priority should be given to natural ventilation and the selection of locally adapted lineages. This flexibility aligns with the principles of “Darwinian beekeeping”, which prioritizes genetic diversity and local adaptation over technical standardization. Ultimately, the beekeeper’s first responsibility is not to insulate the hive, but to strengthen the colony. Healthy, populous colonies with coherent organization create their own microclimate: their vitality is worth more than any technical solution.  

In the long term, the challenge is not to make the hive airtight against cold, but to strengthen the symbiosis between the bee, its habitat, and the climate. Insulation, in this perspective, should be understood not as a shield, but as a dialogue: a subtle adjustment between protection and freedom. Cultivating this trust in the resilience of the living—while accompanying its adaptation—may well be the most promising path towards sustainable beekeeping, aligned with evolutionary biology and respect for natural dynamics.

For nearly one hundred million years, bees have survived glaciations, climatic drift, and upheavals of the Earth by adjusting their collective organization with no help other than their own. Our species, appearing barely two hundred thousand years ago, is only an instant in this long history of life.

Remembering this precedence means understanding that trusting bees also means recognizing the adaptive wisdom that millions of years of evolution have inscribed in their behaviour. True sustainability is born of this trust: the trust that links humans to a form of life that is older and infinitely more experienced.

8. Beekeeping practices and operational recommendations

Before any insulation measure, the beekeeper’s absolute priority must be to ensure colony strength and health before winter. A compact population occupying at least four to six frames well covered with bees has sufficient thermal inertia to maintain its microclimate and withstand cold. Weak colonies, even if perfectly insulated, remain vulnerable to starvation, disease, and thermal imbalance. The main investment must therefore be in stock vitality: young, well-mated queens, sufficient stores, a reasoned Varroa control strategy, and the absence of stress before overwintering.

Practical application of knowledge about collective thermoregulation then requires a reasoned approach to insulation, adapted to climate, population size, and seasonal cycle. The overarching goal remains to reduce winter losses and limit honey consumption without disrupting the superorganism’s natural thermoregulation.

When to insulate?

External insulation is primarily justified in regions where temperatures remain sustainably below –10 °C, or where hives are exposed to persistent cold winds. In temperate areas, a light and breathable insulation is sufficient, or even just protection against wind and precipitation.

Recommended materials

Natural insulators—sheep wool, hemp, or cork—offer an excellent compromise between thermal insulation and moisture permeability, promoting a good hygrometric balance and adequate hive “breathing” (Casado Sanz et al., 2024). These renewable and biodegradable materials integrate well into sustainable beekeeping that respects the environment and bee welfare.

Illustration 5: Natural materials should be prioritized (https://backyardhive.com)

Synthetic materials such as polystyrene or polyurethane do offer high thermal efficiency, but their low permeability can lead to overheating, excessive condensation, and physiological stress for bees (Mitchell, 2023; Sonmez Oskay et al., 2025). In addition, some construction-derived products—plastic foams, composite panels, or aluminium-based sheets—may release volatile compounds under heat that could affect chemical communication or the hive’s microflora. Their manufacture and disposal also raise sustainability and recycling issues that conflict with the principles of ecological beekeeping.

A carefully insulated inner cover, using natural and breathable materials while maintaining effective ventilation, is the most balanced practice: the hive must “breathe”.

Insulating small colonies and nuclei

Small populations have reduced thermal mass; they lose heat more rapidly and therefore clearly benefit from reinforced insulation. The strategy is to reduce the volume to be heated (warm partition and tightened frames), add lateral and top insulation (wool, cork, foil bubble wrap), and maintain slight ventilation to avoid condensation and mould. The goal is to support collective thermoregulation without preventing the winter decrease in activity that bees need for rest.

Supporting spring build-up

In spring, well-modulated insulation can speed up brood resumption. The use of high-performance insulating partitions (PIHP) around the brood nest from late winter promotes a stable temperature around 34 °C and brood homogeneity. This supports nurse development and the creation of breeding nuclei. However, insulation should be removed gradually once outside temperatures exceed 15 °C, to avoid excess heat and premature stimulation of egg laying that can lead to swarm fever.

Risks of overly effective insulation

A hive that is “too warm” maintains prolonged winter activity: no brood break, excessive consumption of stores, continuous reproduction of Varroa destructor, and premature exhaustion of winter bees. These effects echo observations by Minaud et al. (2024), who associate high internal temperatures with increased spring mortality. The central recommendation therefore remains to aim for balance: favour full winter rest rather than permanent artificial comfort.

Winter feeding

Providing fondant (candy) can be useful when there is a risk of starvation, especially during late-winter cold returns. It should, however, be reserved for proven need and not applied systematically. Liquid syrup, which is too stimulating, should be avoided. Excessive feeding involves several risks:

1. unintentional selection of populations dependent on humans;
2. weakening natural selection for lineages adapted to the local climate;
3. transmission of “assisted” genetics that is less sustainable in the long term (Neumann & Blacquière, 2017).

Summary of recommendations

Objective	Recommended strategy	Risks if poorly applied
Reduce winter losses	Partial, breathable insulation if below –10 °C	Overheating, moisture, Varroa proliferation
Support small colonies	Reduced volume + gentle insulation	Condensation if hive is too airtight
Support spring restart	Modular PIHP around brood	Early egg laying, energy imbalance
Prevent starvation	Fondant if genuine need	Selection of dependent populations

 

Insulation is not a universal remedy: it complements natural thermoregulation without replacing it. Priority should remain the health and strength of the population, genetic diversity, and trust in the superorganism’s resilience. Observe, adapt, modulate—never standardize.

 

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