News » 15.01.2026 - Greenhouse damage or crop damage: a dilemma when snow is on the greenhouse roof
Dutch growers have been advised to remove snow from greenhouse roofs as quickly as possible by heating, while keeping the climate screen fully open. The screen should only be closed once the snow on the roof has melted completely. This guidance was issued by a major insurer in response to snowfall in the Netherlands.
Annemiek Bosma, lecturer in Het Nieuwe Telen (Next Generation Growing), also noted the advice but warned growers about the consequences of leaving the energy screen fully open. According to Ton Habraken of climate screen manufacturer Svensson, fully opening the screen is not necessary to effectively melt snow from the greenhouse roof.
Conflicting interests
Climate screens are primarily used to save energy. When the screen is open, energy savings drop to zero, allowing heat to rise directly to the roof to warm the structure and melt the snow. While this is effective for protecting the greenhouse, Bosma points out that it can conflict with maintaining optimal crop conditions.
Insurer Hagelunie acknowledges this dilemma. "We understand the conflicting interests and the challenges growers face," a spokesperson said. "From the perspective of protecting the greenhouse structure, it is essential to reach the right temperature at the top of the greenhouse to melt the snow. How the grower achieves this is ultimately their own decision."
Radiation
"We teach our course participants in Het Nieuwe Telen that preventing crop cooling due to radiation loss is extremely important," says Annemiek Bosma. "With an open energy screen, radiative heat loss is very high: for every degree of temperature difference between the greenhouse roof and the crop, the energy loss is about 5 W. So with a roof temperature of 0°C and a greenhouse temperature of 17°C, the energy loss amounts to 85 W. The crop head becomes cold, which means no calcium uptake, condensation on the crop, and an increased risk of fungal diseases."
Based on the principles of Het Nieuwe Telen, Bosma advises keeping the energy screen closed to around 80–85%. "At that opening, the energy-saving effect of the screen is still zero," she explains. "Screen suppliers will confirm this."
Asked to comment, Ton Habraken of Svensson supports Bosma's point. "An energy screen only starts to deliver energy savings when it is closed by 85% or more," he says. "When melting snow, and with the crop in mind, it is therefore better to set the screen to around 80% rather than opening it fully. Snow will melt just as quickly in that situation."
Choose the right screen position
According to specialists in Het Nieuwe Telen, the greenhouse roof will still warm up sufficiently at a screen position of around 80%, allowing 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," says Annemiek Bosma. "The screen has roughly the same temperature as the greenhouse air and is therefore much warmer than the roof. As a result, energy loss from the crop is much lower. The crop head stays at a better temperature, which is crucial."
Based on experiences during a period of snowfall, Bosma advises: "Snow melting works just as well with a screen opening of 15–20%, while offering much better protection against crop cooling."
Insurer Hagelunie maintains its advice to fully open the screen. "The required temperature is reached fastest when the screen is fully retracted," a spokesperson says. Ton Habraken of Svensson understands this reasoning, noting that with a fully open screen, broken glass cannot fall onto the screen cloth if a pane breaks, preventing additional damage. The question, however, is which risk is greater—technical damage to the greenhouse or damage to the crop—and which leads to higher financial losses in the long term. This is something to evaluate once the snow has cleared, in preparation for future snowfall events.
It doesn't have to be a dilemma
According to Hagelunie, if growers start heating the greenhouse roof in good time, for example, when snowfall is forecast, it may be possible to reach the required temperature beneath the roof with only a limited screen opening. "If the grower has a thermometer installed above the screen, the temperature can be monitored," the spokesperson explains. "An additional benefit is that the grower can also assess the risk of frost damage to the roof."
On behalf of Svensson, Greenhouse Climate Expert Ton Habraken also points to the importance of a measuring unit in the ridge above the energy screen, at a minimum for temperature measurement and preferably also for humidity. Many growers do not yet have such a sensor installed in that position. Habraken encourages them to do so. "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. Insurers might even consider offering a premium discount to growers who have this in place, as they face significantly lower risks during winter conditions."
At Delphy, the greenhouse vegetable team posted a message on LinkedIn about snow, including a tip about the measuring box and a brief discussion about the best way to use screens with snow on the greenhouse roof.
Knowledge from snowy countries
Snow load on greenhouse structures is not unique to the Netherlands, the insurer notes. Growers in other countries also face this type of risk, including Canada. Hagelunie outlines several approaches used internationally.
"When constructing a greenhouse, a grower can choose a heavier structure that does not require active snow melting," the insurer explains. "This is a consideration that Hagelunie risk specialists also discuss with Dutch growers during the planning phase of new builds. If a grower opts not to do this, it is up to the entrepreneur to comply with the greenhouse's operating specifications during snowfall and to ensure the correct temperature beneath the roof to melt the snow."
Using greenhouse heat by opening the energy screen is one option, but it is not the only solution, Hagelunie adds. Alternatives include installing heating hoses in the gutter or heating pipes above the energy screen. "This is a technique commonly used in Canada," the insurer says. "Together with the installer, growers should look for the solution that achieves the right temperature under the greenhouse roof while remaining optimal for their crop."
Source: www.floraldaily.com
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