Do Greenhouses Work in the Winter?

Owning a greenhouse represents a great investment, especially if you want to be the envy of thousands of gardening enthusiasts all over the world. These devices are great for when you want to grow year-round, extend your gardening season, or growing plants that normally wouldn’t make it in your neck of the woods.

Greenhouses are closed structures with a ceiling made from transparent materials like glass or polyethylene through which the sunlight can reach the inside. They work by trapping in the solar radiation and then promoting its absorption by the soil. Then, the inside becomes warmer than the outside creating a stable environment in which plants can grow within favorable conditions.

But what about greenhouses in the winter? Can they survive these climatic conditions? This is a very common doubt among gardening enthusiasts. And that’s why in this article we’ll talk about how you can extend your growing season and keep your tender plants safe from winter damage using a greenhouse.

Can A Greenhouse Work in The Winter?

So, as we mentioned before, many people ask if greenhouses work in the winter. You may be doubting yourself about whether you should own one or not, you may not know very well if it’s worth it. Because let’s be honest, who’s not afraid of wasting their money?

With this in mind, we have good news for you because greenhouses are marvelous tools for the whole year-round. Truth is that due to their working mechanism they come in very handy for several purposes. You just need to decide what you want to use it for.

Whether you want your greenhouse to keep your summer and spring plants safe or to grow winter vegetables, this device has you covered. All you need to know for starting your oasis for the cold season is the required temperatures for the plants you plan of keeping there. Also, don’t forget to think about the climate you live in, because this will determine some of the methods that you’ll use for maintaining a stable temperature inside your greenhouse.

Up next, we’ll walk you through the way greenhouses work in the winter so that you know what you’ll be purchasing. Then, we’ll show you some of the most common types of greenhouses available and what specifically you can use them for.

How Do Greenhouses Work in The Winter?

As you know, the walls and ceiling of a greenhouse are made of glass or plastic. This enables light and heat into the greenhouse. Yet, when temperatures get too cold, you surely need to keep the inside warm. This is a challenge but here’s how to achieve it:

First of all, you should consider that despite creating a warmer environment, greenhouses do not maintain the heat that’s built up during the day. For this reason, you should have a determined method to keep the appropriate temperature for your plants to make it through the night when it’s colder outside.

There are many ways you can do this. You can use a wood-burning stove to heat the air of the greenhouse or even to heat water that you can then pipe through tubes in the ground near the plants. The latter corresponds to a classic supplemental heating technique that you can also achieve by using a reverse cycle air conditioning.

This way you get a low-cost and effective way to maintain heat within. The way these heaters work is by using natural gas or propane which means that they require no electricity. Thus, they’ll keep on doing their job even if you have a power outage. You just place the heater under a bench and turn on the thermostat and set it to the temperature you want.

Then, during the night the warmth will be evenly distributed among your plants as hot air rises from under the bench. The heater must be at the bottom of the greenhouse so that this method works. This is because hot air is lighter than cold air, so it tends to rise above.

Although this heater method is the most commonly used it isn’t the only one.  For example, you can also place large containers of water inside the greenhouse so that they absorb the heat in the day and give it off during the night. As you can see, these work with the same principle of the heaters but this technique requires you to place your greenhouse in a spot where it gets all the sunlight possible during the day.

Also, another way you can keep the warmth of your greenhouse is by adding an extra layer of insulating plastic around the plants that need to stay warm the most.

Overall, don’t forget that you should keep an eye out for your climatic conditions. And, always place your greenhouse somewhere it gets full days of sun, no matter what method you choose.

Types of Greenhouses

When you think about a greenhouse you may picture a classic glass structure with frames. This is generally what a greenhouse is but you should know that they can also be used for other purposes. Each one requires a specific temperature set and specific isolation maneuvers.

Firstly, greenhouses come in various shapes and sizes. For instance, hothouses and glasshouses usually are middle-sized. They’re very seldom used in the USA because they fit perfectly almost anywhere and are very easy to settle up. A conservatory, on the other hand, is generally a bigger structure usually made of glass that can be attached to your dwelling.

As for a smaller size, we have Cold Frames which are structures similar to a greenhouse to shelter plants. The floor is often dug down in the earth to approximately a foot of depth for the soil to hold heat. Cold frames are the easiest greenhouse models to set up and are perfect for extending your harvestable seasons.

Lastly, something good about greenhouses is that they can either be operated as a hothouse or cool house or even both depending on what you choose to use it for through the year. It doesn’t matter what size you own; you can always set things up to create the perfect environment for your plants.

For example, a hothouse is best used to keep your hot season plants safe. These not only maintain the heat by profiting from sunlight exposure but that also require supplemental heat. This means that the minimum temperature is higher than the one for a cool house, as we’ll explain later on.

Does A Greenhouse Stay Warm in The Winter?

Okay, so now that we’ve stated that greenhouses can be used in winter, how do you know if your greenhouse will indeed stay warm the entire season? Well, you can easily deduct this from the previous info that we’ve given you.

Firstly, since greenhouses profit from sunlight exposure, it doesn’t matter much how many hours of sun there is where you live as long as it has full exposure during that time. Also, the way you isolate the structure to keep the warmth will help on keeping it working during the cold season.

Truth is that you should always be prepared for an unexpected lowering in temperatures through the winter. This means, that despite being able to rely on the heat from the sun you should always have a plan B for the cold season. The good news is that greenhouses are so versatile that you can always choose to make yours a hothouse.

To heat your greenhouse as a hothouse during the coldest weather you will need to consider artificial means. You can use a wide variety of different solutions such as wood heaters, electric space heaters, or portable gas and electric options. Besides, there are even more permanent choices that you may want to consider like installing a thermostat on larger areas for hassle-free heating.

Overall, what’s important is that to have your greenhouse stay warm in the winter, is that you pay attention to every recommendation. Since it’s a great challenge you should take it seriously. Thus, you can easily maintain a beautiful warm spot in your garden by constantly checking on it, making sure the temp is right, and by allowing it full hours of sun.

Greenhouse in a Greenhouse (Method)

Perhaps you’ve heard of nested greenhouses. This term may be confusing but it’s actually very simple as it means that you simply have a greenhouse inside a bigger one. This method profits from the heat of the bigger structure to help to provide better temperature isolation for the smaller one.

As you know, greenhouses work by letting in visible light, which is then absorbed by plants inside while blocking the IR radiation re-emitted by those plants. So, by having a smaller greenhouse inside the bigger ones, the radiation that goes through the bigger structure also passes through the smaller one.

Next, the smaller greenhouse takes up the same light and does its work on the plants inside. Nonetheless, know that the radiation that’s re-emitted by plants in the bigger greenhouse will not get through into the smaller greenhouse for the same reason that they cannot escape out of the bigger one. Therefore, if there are absorbing surfaces inside the smaller greenhouse too, the temperature there will be no greater than inside the bigger greenhouse. This can be explained because temperature transferring only happens from higher ones to lower ones, so if both structures receive the same sunlight but cannot reflect into each other, each one will be the same temperature.

What Temperature Does a Greenhouse Need to Be?

When we talk about keeping a well-maintained greenhouse, we need to assess the topic of how hot it needs to be so that your plants grow healthy. Typically, a greenhouse can be about 30 degrees Fahrenheit higher than outdoor temperatures. However, this can vary depending on your climate, the outdoor temperature, greenhouse glazing, etc.

With this in mind, the ideal temperature inside your greenhouse should be about 80 to 90 degrees Fahrenheit. Any temperature above can seriously damage your plants since greenhouses mainly trap the sun’s rays to heat the interior air, they can quickly heat up. So, you need to be very careful on warm sunny days.

On the other hand, as for colder days, you need to provide good isolation so that the cold doesn’t impair your plants’ growth. Also, you can use an alternative heating source if you live in very cold areas. So, learning how to keep the internal temperature of your greenhouse steady is a must.

How Warm Is A Greenhouse in Winter?

As we’ve mentioned, a greenhouse can be operated in several ways depending on the time of the year. For instance, a hothouse must maintain a minimum nighttime temperature of 55 degrees Fahrenheit or greater. While a cool house has its minimum of 45 degrees Fahrenheit. The maximum temperature is usually around 90 degrees during the day, year-round.

This means that depending on the time of the year your greenhouse will demand more o less heat inside to reach the desired temperature.  So, in winter the colder it is outside, the higher your demand for heat will be inside your greenhouse. Also, consider that soil temperatures should also be checked because they rarely rise above 50 degrees Fahrenheit in the winter months and most plants grow between 65-75 degrees Fahrenheit.

That’s why it is most likely that you’ll require an efficient and properly-sized supplemental heating system, especially for when the minimum nighttime temperature peaks where you live. For example, to help you maintain the ideal temperature, having more snow blanketing your greenhouse can often make a pretty good insulator. Despite sounding counterproductive, dry snow can prevent heat transfer and heat loss from your greenhouse to the outdoors. This is due to all the tiny air spaces between snowflakes that create a barrier that won’t let the icy howling winds of the outside to take any heat from your greenhouse.

So, instead of removing snow from your greenhouse, you should leave it there coating the sides as long as it isn’t wet. Thus, you’ll be allowing your greenhouse to get all the 5 to 6 solid hours sunlight it can get during the day through the ceiling and allowing that heat to remain on the inside. With this system, your plants will be happy at 35 degrees Fahrenheit, and will still be able to grow down to the teens.

Lastly, consider that keeping a close eye to the temperature and inner conditions of your greenhouse are essential. Since certain diseases also love a warm hideaway when the outside is inhospitable. So, your warm greenhouse may be the perfect attraction to them. That’s why you should always balance your humidity and your heat. You can achieve this by either through proper ventilation or effective dehumidifying systems.

Featured image credit: “Deck the Greenhouse” by Rhonda Fleming Hayes is licensed under CC BY-ND 2.0