Treacherous snow

Greenhouses are usually calculated for a limited amount of snow. The weight of snow can vary greatly across the roof of a glasshouse and can easily exceed the maximum load. In case of overload the glass sheets will break or lead to a total collision. How to prevent damage by snow load?

Start immediately with melting the snow
Greenhouses are sometimes calculated (depending on country and situation) on a limited amount of snow. This is acceptable under the condition that the greenhouse is heated and the roof of the greenhouse is uninsulated. In that case there is no buildup of snow because it immediately melts away. You have to maintain a minimum temperature of 12°C directly under the roof.

An uninsulated roof means that you have to open your screen(s)
The screens in greenhouse are highly insulating. Therefore you have to immediately open your screens in case of snowfall. If you don’t, a layer of snow can quickly arise. Snow has an insulation effect. In case of heavy snowfall the accretion will go faster than it melts away at the bottom leading to a situation that you cannot control! Only close the screens after all snow has melted.

Prevent high temperatures of the heating pipes
When you have to open your screens, you probably need your total heating capacity. Prevent damage to your crop due to high temperatures of the heating pipes in close range of the crop. Most crops usually can withstand low temperatures. In situations where you have to go to total heating capacity it’s important to ensure that the transition in temperature is as gradual as possible to prevent condensation on the plants. A safe rule of thumb for increasing heat up is 1°C per hour.

Calculate the heat capacity without the use of the screen
As mentioned before the minimum temperature under the roof must be 12°C. Calculate the capacity of the total heat installation (gas, boiler(s) and heating pipes) on this 12°C without the use of screens.

Calculate your greenhouse on a heavy snow load
Instead of an uninsulated roof you can choose for a design based on a heavy snow load comparable to the commercial buildings. In that case it is not necessary to open the screens and to melt the snow immediately. This can be mandatory by your local building codes.

What to do in case it goes wrong?

• Report your damage directly to Hagelunie (0031 71 568 99 55) and inform your broker.
• If you have to increase your need for natural gas (due to the damage) and you will exceed your gas contract, this might result in a penalty. Inform your provider and call on force majeure.
• Make an inventory of the broken sheets. Try to repair the holes provisionally or with repair sets.
• Mark the sheets that need to be repaired. It’s convenient for the repair team to be able to see where the wires of the screen needs to be replaced, and for food safety where to harvest or not.

If you what to know more?
Don’t hesitate to call or send us an e-mail.