Growing in Winter

Winter Greenhouse

Winter Greenhouse

If you want to grow food consistently through winter, having the right greenhouse structure should be at the top of your list.  Having a good greenhouse design will go a long way toward being able to grow successfully in winter.  

Growing food in a greenhouse in the winter!  Is it even possible?

Absolutely it is possible to grow food through winter inside a greenhouse.  Being successful has quite a bit to do with the greenhouse structure itself.  Winter weather presents challenges from gale-force winds, heavy snow loads, and extreme temperature swings.  Like you, plants prefer a cozy place to shelter from the cold.  Below I will provide an overview of the design you need to consider for a Winter Greenhouse.

Sunglo Series-10 located in Alaska

Sunglo Series-10 located in Alaska

Winter Greenhouse Design Considerations  

Snow Load

Growing up in Michigan I have found memories of shoveling copious amounts of snow from the driveway.  It doesn’t take you long to realize that snow is heavy.  As a general rule, saturated snow weighs approximately 20 pounds per cubic foot or 1.25 pounds per square inch of depth.  Easily you could envision how quickly the weight adds up as it collects on top of your greenhouse.  When deciding on a greenhouse design it is wise to consider how snow load impacts my greenhouse so it doesn’t collapse under the weight.  The strength of a greenhouse is dependent on the materials it is composed of such as framing material and the design elements such as truss spacing and roof pitch. 

Greenhouse companies will use lumber, PVC, aluminum, and galvanized steel for the frame.  Each of these contributes to the overall strength of the building.  Steel is the strongest material but over time even if galvanized it will begin to rust inside a greenhouse.  Wood is also challenging to use inside a greenhouse as it will degrade quickly in a humid environment unless constantly maintained.  There are greenhouse kits and plans available that make use of PVC for its framing as it was once readily accessible and cheap.  However, that is not the case anymore as prices have increased in recent years.  PVC will not offer the protection needed for high snow loads and degrades quickly in the sun. Aluminum is a very robust material having a superior strength-to-weight ratio as compared to steel with the added benefit it doesn’t rust.  

When choosing a winter greenhouse the design of the building itself is very important.  Just because it is built with steel does not mean it’s necessarily stronger in regards to snow load.  A critical factor in being able to support a large snow load is dependent upon the spacing between the roof trusses and purlins.  Greenhouses are offered in many truss spacing options so if you live in an area that can potentially receive heavy snow loads I suggest you choose a greenhouse design with a narrower truss spacing of 4 feet or less.   The shape of the greenhouse is an important consideration as to how it pertains to the building’s ability to shed snow off the roof.  A flat pitch tends to hold the snow versus a steeper rounded pitch which will easily shed the snow.  The Quonset design provides the best winter greenhouse design for shedding snow.

Wind 

Wind tends to occur more and is stronger during winter so your winter greenhouse will need to be able to withstand winter winds.  Building shape plays a critical role along with the materials previously discussed.   Consider the height and dimensions of the building.   A lower and rounded profile is less likely to experience damage.  Be aware that there are also other factors in play here that will determine wind impacts, site location, greenhouse orientation, and geographical climate.  Pay attention to how the greenhouse framing is connected together and how it contributes to the overall strength of the design.  Particularly you will want a greenhouse that can easily be anchored into the ground or foundation securing it from blowing away in high winter winds.  A quality greenhouse kit will contain detailed foundation guides detailing how to anchor the building to protect against high wind environments.

Extreme Temperatures

When most people consider growing in winter their main concern is protecting the plants from freezing temperatures.  A winter greenhouse must be well constructed and provide enough insulation to protect the plants from cold temperatures.  A quality winter greenhouse when assembled will contain no gaps to allow heat to escape and allow cold air to enter freely.  At the same time, the walls and greenhouse covering (glazing) need to provide insulation in order to efficiently maintain a set temperature.   Greenhouses are typically glazed with three different types of material, polyethylene film, polycarbonate, and acrylic.  These materials are offered in different thicknesses and choices which ultimately determine how much insulation they can provide.  Listed in order of worst to best in regard to insulating properties are 6 mil polyethylene film, 0.57” acrylic, and 8-mm twin-wall polycarbonate.  Which greenhouse glazing option is more insulated ultimately is determined by its manufacturing, application, and thickness.  Some greenhouses will be designed to use multiple layers or different thicknesses which will change the final insulation properties. Therefore it is best to find the specifications listed by the greenhouse manufacturer.  Please be aware that if a greenhouse is only offered in 4 mm or 6 mm double-wall polycarbonate panels it should not be considered a winter / 4-season greenhouse.  

In addition, it is also important to note how this glazing is attached to the greenhouse.  How is it secured to the greenhouse framing to prevent it from being blown away or ripped off by the wind?

What’s the best choice for my Winter Greenhouse?

Ultimately that answer will be different for each grower and their goals.  Consider each of the items mentioned above when making your decision.  A Sunglo Greenhouse meets all of the requirements.  Our greenhouses were designed by Boeing engineers to create a dependable all-weather backyard greenhouse that a grower could confidently use all four seasons, especially in winter.  A Sunglo Greenhouse is made with aluminum framing with the trusses on 30-inch centers.  Combining the strength of aluminum with a shorter truss spacing gives it the ability to withstand heavy snow loads.  The framing is connected with rivets with the glazing securely attached with vinyl clips and we provide foundation details and options for high-wind load sites. Sunglo Greenhouses are rated to be able to withstand 80 mph winds, but we have heard from many customers that their Sunglo’s have survived 100 mph, and even 107 mph without even leaking!  Sunglo Greenhouses are a Quonset profile and snow easily slides off the smooth outer acrylic panel.  We have greenhouses located geographically notorious for harsh winter environments from the Pacific Northwest, Colorado, and Alaska. 

Grow 4 Seasons in a Sunglo Greenhouse

We are the only greenhouse company to offer an exclusive ‘Winter Package’ to those gardeners that want to grow year-round successfully even in the coldest climates. Our winter greenhouses use three layers of acrylic with a corrugated middle layer making Sunglo one of the highest-insulated greenhouses available.  Also included are raised gardening beds sized to your specific greenhouse with built-in geothermal technology that supplies passive solar heating to the root zone (GAHT® Lite), a 1000 Watt infrared radiant heater with hanging assembly, and includes all the power & temperature controls necessary to run the system.  

If you have questions regarding our Sunglo Greenhouses or want to speak with a Sunglo Owner who has been growing in a winter greenhouse please contact us at  720-443-6711.

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