Greenhouses allow you to grow beautiful plants, even tropical fruit if you live in a colder country or a different region of the world. Thousands of people around the world have them in their gardens, or even garages, yet if you live in a colder area a common concern is: do greenhouses work in the winter?

Yes, greenhouses work during winter, but to do so they need to have a specific temperature to allow you to grow plants. To maintain an adequate temperature, if you live in a very, very cold country, you will need to heat the greenhouse in some way. A cold winter, or cold country is essentially a place where the temperature drops below 0 degrees Celsius or 32 degrees Fahrenheit.

For a greenhouse to work during winter you want it to remain at a temperature not lower than 2 degrees Celsius or 36 degrees Fahrenheit. Ideally, you will want it to remain at no less than 10 degrees Celsius or 50 degrees Fahrenheit. That will allow you to grow pretty much anything you want.

How Does A Greenhouse Work?

It might seem obvious, but understanding how does a green house work is key to answering the first question: does a greenhouse work in winter?

Well, greenhouses are essentially a house shaped structure with transparent walls and roof that lets in as much light as it can, to then trap the heat and turn it into warm air inside the greenhouse itself. This warm air allows you to keep a stable temperature inside the unit, thus creating or recreating an environment favorable for the growth of plants, crops and other flora.

It’s key that the walls and roof are transparent to allow the rays from the sun to pass through and heat what’s inside the greenhouse, which can be plants, soil or even water (more about this later).

Unheated Greenhouse Winter Temperature

Leaving your green house unheated during winter, exposes your crops or plants to a very low temperature. As we mentioned above, it will always depend on what you are growing, but you won’t want the temperature to pretty much ever go below 2 degrees Celsius or 36 Fahrenheit. Even better, you don’t want it to drop from 10 degrees Celsius or 50 degrees Fahrenheit to be on the safe side.

The problem is that on places such like Zone 7, you can be looking at -15 degrees Celsius at times, with little sunlight during cloudy days. Therefore, if you just leave the greenhouse fully unheated, without any thermal mass, not good enough insulation, then the crops you’ll be growing are close to none.

How To Heat A Greenhouse Without Electricity?

Now that we have established what a greenhouse is and why it’s important that it let’s not just light in it, but traps heat to keep a stable temperature, we can look into how to make it work during winter.

It’s obvious that a heater is the best choice, and we’ll talk about it in the next section, but first let’s look at a way to heat a greenhouse without electricity.

Thermal Mass

The answer is by creating thermal mass. And what is thermal mass? Thermal mass can be achieved by putting large barrels filled with water (preferably black to attract more heat) inside your greenhouse, so the water heats up and then releases it slowly at night or when there is no more light.

The problem and main issue is that using thermal mass is not that simple. Depending on the size of your greenhouse, you might not have the room to store all these barrels or dense objects that warm up during the day. Even if you have the room inside the greenhouse, you might have to sacrifice a lot of it just to fit enough barrels to keep a stable temperature.

Therefore, you might want to do a few things:

Insulate Winter Greenhouse Kits

These are green house kits with double walls for insulation. If it’s made of glass, you have double-walled glass, of its polyethylene (PE), you get double walled polyethylene sheets, or add bubble wrap or even add silicone to the sides and corners to create as much insulation as you can.

The concept of the double layer of walls is to leave a thing gap between each wall, this gap is just trapped air that acts as an insulator. If you end up getting a PE green house, know that PE panels are natural heat insulators, which make them one of the best materials for winter greenhouses. On top of that, if you can get a 4 wall construction on both the roof and sides, you will get an even better heat retention than just double walls. However, that can be expensive.

Do keep in mind one last important thing: if you live in an area with a lot of snow fall, rain fall or wind, your greenhouse must have a strong structure to handle the weight of the snow, the strength of the wind and rain. Make sure you buy ir build accordingly!

Wood Fired Heat For Greenhouses In The Winter

It sounds crazy, but it works. Now, it can be slightly dangerous to use wood fire inside a closed space, but even a regular heater can be slightly dangerous. Make sure that if you use this method, you are using a smaller masonry heater type or a camping stove, that’s stable, won’t fall, and it’s not really burning that much, but rather just heating the greenhouse during the evening. You will need to play with it a bit to find the right temperature.

Now depending on how much you want to dedicate time and investment to your green house, well, you can even go with more creative solutions such as adding clay walls to surround the greenhouse, trap heat and keep a stable temperature. Here is a great article on how they do it in Alberta, Canada.

The Best Way To Heat A Greenhouse During Winter

Get a heater. Period. That’s the best way to do so. There are countries where you can do some creative things, such as in Iceland where they use renewable geothermal energy to power their heaters and make sure the greenhouses have excellent temperatures to grow even tropical fruits. However, that’s not the case everywhere.

For many, having a greenhouse can be a hobby, meaning the greenhouses are in their garden, and as such you will want a heating system. Sure, the heating system can be powered by solar panels to an extent, but be prepared to see a spike in your power bill, unless you find other solutions such as oil and diesel powered heaters. Regardless, it’s an expense you need to consider.

Depending on the dimensions of your greenhouse, then the heater you use will consume more or less energy. Make sure to get your calculations right.

Garage Greenhouse Winter Solution

Another option is to have a garage greenhouse, but this is not for everyone or every crop. If you live in a place with too much rainfall or snow fall, you want to avoid accidents, and you have the money, then you can keep your green house inside your garage and use grow lights.

Grow lights in their own provide UV light as well as heat, in order to help plants grow. It’s not a secret some types of plants are grown with these even in really dark places.

Winter Greenhouse Crops

Are there suitable crops for winter that won’t require such a warm temperature? Of course, and this is perhaps a smart thing to do: aim to grow winter crops that grow at lower temperatures.

• Kale, arugula, collards and other plants that are considered leafy greens grow during winter or colder temperatures.

• Root vegetables such as carrots, beets and even potatoes also grow at lower temperatures.

• Brassica plants such as spinach, cabbage and winter lettuce are perfect too.

• And don’t forget the “smelly” favorites of the season: Brussel sprouts and garlic!

To wrap it all up, you can have a greenhouse working fine during winter. It might take some work, or some extra money, but it’s a hobby and job we all know it’s 100% worth it. You might get creative and suddenly be running some ideas on how to heat it better, but all in all, you can make it work!