10 Snow-Related Causes Of Greenhouse Failure

If structures are spaced too closely together, snow removal equipment cannot get in between them.  Photo by John Bartok, Jr.

John Bartok Jr., an agricultural engineer and University of Connecticut Professor Emeritus, says snow varies considerably in consistency and weight. It can be light and fluffy with a water equivalent of 12 inches equal to 1 inch of rain. Snow can also be wet and heavy with 3 to 4 inches equal to 1 inch of rain.

Snow having a 1-inch rainwater equivalent loads a structure with 5.2 pounds per square foot. This amounts to about 6.5 tons on a 25- by 96-foot greenhouse.

Bartok says there are several reasons for structure failures during snow storms.

1. Drifting Snow: In nor’easter storms, adjacent greenhouses or bays of gutter-connected houses that have a north-south ridge orientation tend to collect more snow on the leeward side. Snow that is lifted over the ridge of the first house can be dumped on the windward side of the second house. This creates an off-center load on the roof.

2. Proximity Of Adjacent Greenhouses: Building greenhouses too close together is a common cause of failure. This is especially the case with overwintering structures that are only 4 to 6 feet apart. When snow slides off the greenhouse roof, it fills the space and crushes the house’s sidewall frame. Usually there is inadequate space to get in with a bucket loader to remove it. To save the structure, some growers cut the plastic covering to allow the snow to flow into the greenhouse and relieve the pressure. Other growers install two-by-fours to brace the side frame.

3. Greenhouse Frame Shape: The gothic-shaped greenhouse was developed to eliminate the flat spots that can collect snow on the top of hoop-shaped structures. Since 1994, when the nursery industry changed from the hoop design to a gothic design for overwintering structures, there have been fewer structure failures.

4. Poor Frame Connectors: Check and tighten all bolts and tek screws before the winter season. These fasteners tend to loosen over time. Brace bands and u-clamps can slip if they are not held in place with tek screws. The screws should be at the side of frame members, not at the bottom. Several greenhouses have failed at the point where tek screws were placed at the bottom of hoop tubing. This created weak spots.

5. Greenhouse Frame Racking: Many manufacturers do not include bracing with their greenhouse kits. All greenhouses should have diagonal braces from near the peak at the endwall to the baseboard about 16 to 20 feet from the endwall on all four corners. This provides stability and keeps the frames vertical. Frames lose considerable strength when they are not vertical. Install tubing or a 1- by 4-inch board and secure with a U-bolt at each hoop.

6. Poor Welds: Welds that are not continuous or that have burned through the metal are weak spots. Areas that should be checked include truss braces, welds between sections of gutters and tubing sections that are welded together without an insert. Although expensive, professional inspection and x-ray testing may be worth the added expense.

7. Inadequate Air Inflation: Heavy wind can create rippling of plastic coverings causing failure at the structure attachments. This can be prevented by increasing the polyethylene film’s inflation slightly by opening the blower’s intake valve. Make sure any holes or rips are taped. Check to see that the inflation fan intake cannot be blocked by snow.

8. No Heat Or Inadequate Heat: Most greenhouses that fail don’t have heat or were heated to 40ºF or less. When heavy snow is predicted, the greenhouse heating system should be turned on and the thermostat set at 70ºF or higher. Energy screens should be left open. The few extra gallons of oil or therms of natural gas burned are less expensive than replacing a collapsed greenhouse.

9. Open Vents, Doors Or Louvers: The effective force of the wind is doubled when it is allowed inside a greenhouse. Latch doors and tape vents and shutters so that they cannot open.

10. Plugged Gutters And Downspouts: Once snow has accumulated, it is important to have provisions for its removal. Removing snow from the roof lets some light in, allowing warming of the inside. This causes some melting, which helps to reduce the snow load. Once the snow is melted, it is important to keep the gutters and downspouts free of ice. Ice socks filled with calcium chloride placed in gutters and downspouts will melt the ice. If available, magnesium chloride or sodium acetate is more environmentally friendly and reduces corrosion.

Shoveling is not always the answer. It can be very expensive to remove the snow. You also need space to dispose of it. If the snow is light, there is not much danger of collapse. If the snow is heavy, some growers have found that as it settles, melts and refreezes, it forms a cocoon next to the plastic covering and doesn’t put a lot of pressure on the greenhouse. Removing it may cause more damage.

Leave a Reply

One comment on “10 Snow-Related Causes Of Greenhouse Failure

More From Structures...
Emerald Coast Growers Seed RoomTight feature

March 22, 2017

An Inside Look at Emerald Coast Growers’ New Seed House

Florida-based liner producer Emerald Coast Growers custom retrofitted and expanded an existing greenhouse, with the goal of increasing production efficiency.

Read More
Lemnis Oreon Lights

March 21, 2017

Lemnis Oreon, EnviroTech Cultivation Solutions to Partner on LED Distribution

EnviroTech’s expertise in energy and water technology fits perfectly with the water-cooling solution of Oreon Grow Lights, according to the companies.

Read More
Brian Munchel

March 18, 2017

Brian Munchel of Ludy Greenhouse Manufacturing Dies at 48

Munchel, a long-time member of the National Greenhouse Manufacturing Association, worked at Ludy Greenhouse Manufacturing for more than 30 years and was a computer-aided draftsman.

Read More
Latest Stories
Brian Munchel

March 18, 2017

Brian Munchel of Ludy Greenhouse Manufacturing Dies at …

Munchel, a long-time member of the National Greenhouse Manufacturing Association, worked at Ludy Greenhouse Manufacturing for more than 30 years and was a computer-aided draftsman.

Read More
Nexus Atrium for Prides Corner

March 15, 2017

How Tech Suppliers Are Helping Growers Find Solutions

Greenhouse structures and components manufacturers highlight some of their most recent projects.

Read More

February 15, 2017

Growers Planning to Invest in Structures in 2017

Data from this year’s Greenhouse Grower State of the Industry survey indicates that growers are planning to make major investments in structures and facility upgrades this year.

Read More
NVAC Greenhouse prototype

February 15, 2017

New Greenhouse Cooling System in Development for Hot-Cl…

Researchers at McGill University in Quebec have developed an alternative evaporative cooling solution for greenhouses in warm climates, and are now seeking commercial partners.

Read More

February 15, 2017

Registration Open for NGMA Spring Meeting

The annual gathering of the National Greenhouse Manufacturers Association will feature a look at green industry trends, emerging market opportunities, and more.

Read More
EFTE Film

January 18, 2017

Looking at Glass or Polyethylene for Your New Structure…

Ethylene Tetrafluoroethylene, also known as EFTE, is a fluorine-based material that looks like a standard polyethylene greenhouse film but offers high light transmittance.

Read More
Nadia Sabeh, CEAC

January 18, 2017

Upcoming Seminars to Focus on Managing the Greenhouse E…

The seminars, which will also be accessible online, are presented by the University of Arizona’s Controlled Environment Agriculture Center.

Read More

November 16, 2016

Stay Up To Date On Greenhouse Structures And Materials

eGro, an online resource for greenhouse growers, features a series of video lectures and tutorials on a wide variety of topics, including greenhouse structures and terminology, heating and cooling, and more.

Read More
Dual Atrium Greenhouse (Nexus)

October 12, 2016

Gibraltar Industries Acquires Nexus Corporation

The building manufacturer and distributor strengthens its position in the U.S. greenhouse market, complementing its RBI greenhouse company with the aquisition of Nexus Corp.

Read More
Gotham Greens Atrium Style Greenhouse Chicago

September 14, 2016

How An Energy Audit Of Your Greenhouse Can Save You Mon…

Is your greenhouse utility bill getting you down? Consider an energy audit to evaluate potential energy savings.

Read More
JGS Structure at Vineland

September 14, 2016

Take A Virtual Tour Of Canada’s Vineland Greenhouse Tec…

The one-of-a-kind research greenhouse project was completed by JGS Limited and features 40,000 square feet of horticultural research space.

Read More
Stuppy Greenhouse Manufacturing's Rainbow Super Structure

September 14, 2016

NGMA Contributes Revisions And Updates To Building Code…

The revisions cover the definition of a greenhouse, improved efficiencies in making greenhouse code changes, and more.

Read More
GrowSpan Light Deprivation Greenhouse

August 25, 2016

New Light Deprivation Greenhouses Help With Light Manag…

The GrowSpan light deprivation greenhouse from Growers Supply is outfitted with a blackout system that provides growers with control over the light cycle.

Read More
Cannabis Structure

August 23, 2016

5 Factors To Consider In Your Cannabis Structure

Along with the size and specs of your greenhouse, it's also important to focus on ventilation, light deprivation, benching, irrigation, and odor control.

Read More
Nexus Dual Atrium at Lucas Greenhouses

August 15, 2016

6 Ways Greenhouse Suppliers Are Partnering With Produce…

Greenhouse and equipment manufacturers share how they work with growers to provide customized solutions.

Read More
Cannabis Structure

July 28, 2016

How To Maximize The Efficiency Of Your Cannabis Structu…

The up-front costs of creating your cannabis facility may be high, but at least one expert says making the investment now will be well worth it down the road.

Read More
Floral Greenhouse at Vineland Research Centre

July 20, 2016

Research And Commercialization Unite At The New Vinelan…

The new, pre-scale commercial greenhouse facility at Vineland Research and Innovation Centre in Vineland Station, ON, will help accelerate the commercialization of innovative technologies and products coming out of research.

Read More
Geranium Injured By Ethylene

July 20, 2016

How To Prevent Greenhouse Heating Leaks

Ethylene from malfunctioning greenhouse heaters can lead to crop injury, while carbon monoxide can lead to worker illness. Know the symptoms and how to check greenhouse heaters to avoid these concerns.

Read More