In response to frequent snowfall in the Netherlands, major agricultural insurer Hagelunie has issued targeted guidance to local greenhouse growers on greenhouse snow removal—specifically, melting snow accumulated on roof surfaces quickly through internal heating while adjusting greenhouse climate screen positions, and closing the screens only after the roof snow has completely melted and the structure is no longer at risk. This recommendation is rooted in the insurer’s goal of minimizing snow-induced structural damage to greenhouses, which can result in costly repairs and long-term production disruptions. However, it has sparked intense disputes among industry experts, with conflicting views focusing on the delicate trade-off between ensuring greenhouse structural protection and maintaining optimal crop growth conditions during the greenhouse snow melting process.
Annemiek Bosma, a senior lecturer at Het Nieuwe Telen (Next Generation Growing), a leading institution in agricultural innovation, acknowledged Hagelunie’s guidance but issued a clear warning about the potential adverse effects of keeping energy screens fully open for prolonged periods. Ton Habraken, a technical expert from renowned climate screen manufacturer Svensson, echoed this concern, adding that fully opening the screen is not a necessary prerequisite for effective greenhouse snow melting, and the greenhouse climate screen position for snow removal should be flexibly adjusted based on specific crop types and growth stages. Energy screens (a common synonym for climate screens) are primarily designed to conserve energy by retaining heat within the greenhouse, and fully opening them eliminates this core benefit entirely, allowing internal heat to rise directly to the roof to warm the structure and melt snow efficiently. However, Bosma pointed out that this practice directly conflicts with the need to maintain stable, favorable growing conditions for crops—a critical dilemma that Hagelunie has openly acknowledged.
A spokesperson for Hagelunie further elaborated on the insurer’s stance, stating, “We understand the conflicting interests and the unique challenges growers face when balancing structural safety and crop health. From agreenhouse structural protection perspective, it is absolutely essential to reach the right temperature at the top of the greenhouse to melt snow quickly and prevent excessive load. However, how the grower achieves this target temperature is ultimately their own decision, as they are most familiar with their operations and crop needs.” This position reflects Hagelunie’s priority on mitigating structural risks while granting growers the autonomy to implement solutions that align with their specific circumstances.
Bosma emphasized that preventing crop cooling caused by radiative heat loss in greenhouses is a core principle taught in Het Nieuwe Telen’s training programs—a key factor in balancing effective greenhouse snow removal and sustained crop health. She explained that a fully open energy screen leads to drastically high radiative heat loss, with a measurable and impactful correlation: for every degree of temperature difference between the greenhouse roof and the crop canopy, the energy loss amounts to approximately 5 watts. To illustrate this with a real-world scenario, if the external roof temperature is 0°C and the internal greenhouse temperature is maintained at 17°C—a standard setting for many greenhouse crops such as tomatoes and peppers—the total radiative heat loss reaches 85 watts. This significant heat loss cools the crop heads, which disrupts the plants’ ability to absorb calcium, a vital nutrient for cell structure and growth. Additionally, the temperature disparity causes condensation to form on crop surfaces, creating a moist environment that significantly increases the risk of fungal diseases like powdery mildew and botrytis—all of which can severely impact crop yield and quality, leading to substantial financial losses for growers.
Greenhouse Climate Screen Position for Snow Removal
Bosma proposed a balanced alternative for greenhouse snow removal that prioritizes both structural safety and crop health: keeping the greenhouse climate screen closed to around 80–85%, which translates to a 15–20% opening. This position ensures that heat can still rise to the roof to melt snow effectively while minimizing excessive radiative heat loss. “At that specific opening percentage, the energy-saving effect of the screen is still zero, so growers do not sacrifice snow melting efficiency,” she clarified, a claim that is widely confirmed by leading screen suppliers in the industry. Habraken from Svensson fully corroborated Bosma’s point, noting that energy screens only begin to deliver tangible energy-saving benefits when they are closed by 85% or more. “When melting snow, and with the crop’s well-being in mind, it is therefore far better to set the screen to around 80% closed rather than opening it fully. Snow will melt just as quickly in that situation, but the crop is protected from harmful cooling,” he emphasized.
Balancing Greenhouse Snow Melting and Crop Health
Specialists at Het Nieuwe Telen have further validated this moderate screen position through rigorous testing and real-world observations, confirming that an 80% closed screen still allows sufficient heat to reach the greenhouse roof, enabling snow to melt just as effectively as with a fully open screen. “With the screen closed to 80–85%, radiative heat loss and crop cooling are significantly reduced compared to full opening,” Bosma explained. “The screen itself absorbs heat from the greenhouse air, resulting in a temperature that is roughly the same as the internal air temperature and therefore much warmer than the cold roof surface. As a result, energy loss from the crop canopy is drastically lower, and the crop heads stay at a more stable, favorable temperature—which is crucial for maintaining healthy growth and preventing yield losses.” Drawing on practical experiences during recent snowfall periods in the Netherlands, Bosma stressed that a 15–20% screen opening consistently achieves effective snow melting while providing far better protection against crop cooling and related issues.
Despite these compelling expert recommendations, Hagelunie has maintained its original advice to fully open the climate screen during snowfall. A spokesperson for the insurer defended this position, stating, “The required temperature to melt snow quickly is reached fastest when the screen is fully retracted, which minimizes the time the greenhouse structure is under snow load and reduces the risk of structural failure.” Habraken from Svensson acknowledged the rationale behind this stance, noting an additional practical benefit of full screen opening: if a greenhouse pane breaks due to snow pressure or cold, a fully open screen prevents broken glass from falling onto the screen cloth, avoiding secondary damage to the screen itself which can be expensive to replace. However, he raised a critical question for growers to consider: which risk poses a greater threat in the long term—technical damage to the greenhouse structure or harm to the crops—and which one will result in higher financial losses? He stressed that this evaluation should be conducted thoroughly after each snowfall event to inform more effective preparedness strategies for future winter weather.
Hagelunie also offered a practical path to resolve this apparent dilemma, suggesting that growers can reach the required roof temperature with only a limited screen opening if they start heating the greenhouse roof in good time—ideally 24 to 48 hours before snowfall is forecasted. “If the grower has a thermometer installed above the screen, the temperature in the roof space can be monitored in real time, ensuring it stays at the level needed to melt snow without overheating,” the spokesperson explained. “An additional benefit of this setup is that the grower can also assess the risk of frost damage to the roof structure, which is another common winter hazard for greenhouses.” Habraken, serving as Svensson’s Greenhouse Climate Expert, further emphasized the importance of installing a comprehensive measuring unit in the greenhouse ridge above the energy screen. At a minimum, this unit should measure temperature, and ideally, it should also monitor humidity levels to provide a more complete picture of the roof space environment. He noted that many Dutch growers currently lack such sensors in this critical location and strongly encouraged them to invest in installation. “With a measuring unit like this, growers can accurately monitor whether the chosen screen opening is sufficient to achieve the required temperature above the energy screen to clear snow from the roof, while also keeping crop conditions stable,” Habraken said. He even proposed that insurers might consider offering premium discounts to growers who have this equipment in place, as they face significantly lower overall risks during winter conditions. Additionally, the greenhouse vegetable team at
Delphy, a prominent agricultural consultancy, posted a message on LinkedIn addressing snow-related challenges for greenhouses, which included a specific tip about using such measuring boxes and a brief discussion about the best way to adjust screens when dealing with snow on greenhouse roofs.
Greenhouse Snow Load Solutions from Global Practices
Hagelunie noted that snow load on greenhouse structures is not a challenge unique to the Netherlands; growers in many other countries with cold, snowy winters, including Canada, face similar risks and have developed diverse solutions to address them. The insurer outlined several effective approaches used internationally to manage snow load on greenhouses. One key option is constructing greenhouses with a heavier, more robust structure that can withstand significant snow accumulation without the need for active snow melting. This approach involves using stronger framing materials, reinforced glass panels, and optimized roof angles to shed snow naturally. “This is a consideration that Hagelunie’s risk specialists also discuss in detail with Dutch growers during the planning phase of new greenhouse builds, as it can reduce long-term winter risks,” the insurer explained. For growers who opt not to invest in a heavier structure—often due to higher upfront costs—it is their responsibility to strictly comply with the greenhouse’s operating specifications during snowfall and to ensure the correct temperature is maintained beneath the roof to melt snow effectively and prevent excessive load.
The insurer further added that using internal greenhouse heat by opening the energy screen is just one of many viable solutions for greenhouse snow removal. Alternative methods that can better balance structural safety and crop health include installing heating hoses in the greenhouse gutters or heating pipes directly above the energy screen— a technique that is widely used and proven effective in Canada, where heavy snowfall is a regular winter occurrence. “This external heating approach targets the roof space directly, melting snow without relying on internal heat that is critical for crop growth,” the insurer explained. “Together with their installation partners, growers should evaluate all available solutions and select the one that best achieves the right temperature under the greenhouse roof to melt snow, while remaining optimal for their specific crop types and growth cycles.” Ultimately, the ongoing debate highlights the need for growers to adopt tailored, risk-assessed strategies that balance greenhouse structural protection and crop health. Technological tools like temperature and humidity sensors play an increasingly vital role in enabling informed decision-making, helping growers navigate winter weather challenges while minimizing losses and maintaining productivity.
