How To Heat A Greenhouse During Winter? 5 Facts You Should Know


There are a lot of different methods to heat up a greenhouse during the winter. Today you can use everything from water to compost and solar panels to heat a greenhouse during the winter.

It is important to keep a decent temperature in your greenhouse in the winter, otherwise you can not grow anything in the winter due to the long, cold nights that cause the temperature to drop.

We will try to make you wiser on the various options below in this article.

How to Heat a Greenhouse During the Winter With Water

It’s actually possible to heat up your greenhouse during the night in the winter period without electricity – believe it or not.

Lining one of your walls with black and filled jugs or barrels with water will keep your greenhouse warm and cozy during those long cold winter nights.

In the daylight when the sun is shinning at the greenhouse the water in the filled jugs or barrels will be able to absorb the heat from the sun and use the energy to heat up to water.

However, when the sun goes down again during the day, you will be able to see that the heat from the water in the filled jugs or barrels will be released into the greenhouse and heat it up.

Both plastic jugs and glass containers can be used, but you have to expect that the plastic jugs tend to break down over time and glass containers are breakable but will of course last longer.

Everyone can do it by following these 5 easy steps.

Step 1 – Try to figure out which wall in your greenhouse receives the most sun and collect your jugs or barrels to completely cover the wall. This is important if you want to have success with this method.

However, it can be a great idea to use either milk jugs or glass bottles if you live in a typically cloudy area. By using small containers they will be able to absorb heat faster due to the higher ratio of surface area to volume.

When you have chosen which containers you want to use, you have to clean them with hot soapy water and afterward rinse the containers well with clean water to make them as clean as possible.

Step 2 – We recommend you place the jugs or barrels directly on the floor in your greenhouse for the best performance. Some may use a shelf if they use glass bottles, but if you don’t I would suggest just taking the shelf down in your greenhouse to get better terms for your barrels or jugs.

Step 3 – It’s now time to black spray paint your jugs or barrels if they are clear. As an alternative you can add a few drops of a black fabric dye, if you have the opportunity to get hold of this or if you are lucky enough to be able to buy yourself an already black barrel or jug, then we recommend this.

Step 4 – When your jugs or barrels have been painted or if it’s already black then it’s time to stack your containers along the wall in your greenhouse. When stacking your containers you will build a wall of blackened water-filled jugs or barrels, which are ready to be used to heat up your greenhouse.

Step 5 – It’s time to fill up the jugs or barrels with water. This can easily be accomplished with a water hose and afterward, you have to secure the lids on the barrels or caps onto the jugs.

The last thing you have to do is check the water levels of the barrels or jugs because over time the water will start to evaporate and you will therefore need to refill your containers with water again.

As many of us know it can be hard to heat a greenhouse during the cold winter months, this is a great solution to heat a greenhouse in winter without electricity as well.

How can I heat up my greenhouse for free?

The only way to heat up your greenhouse for free is by doing it from passive solar heat, which we have explained above, where you collect heat from the sun’s radiation during the daytime when the sun is shining and release the heat into the greenhouse during the nighttime.

This can be done in many ways, but the most important thing here is that it’s a thermal mass that is capable of absorbing and holding the heat for a longer period, otherwise you will lose the heat and not be able to heat up your greenhouse for free.

One technique as mentioned earlier in this article is to line the north wall in your greenhouse with black water containers.

When you place the black containers with water on the north wall, the containers will not shade light from reaching the plants in the greenhouse, but will instead be able to absorb light and heat that passes through the greenhouse to the north wall.

When the sun will do down every day, the heat that is held by the water will slowly start to evaporate into the greenhouse, which can heat up your greenhouse for free.

How many water barrels does it take to heat a greenhouse?

If you want to try to heat up your greenhouse with water in barrels, it can be hard to find out how many you actually need. There is a huge difference in the total amount of water-filled jugs you need compare to barrels.

But do not fear, we have a smart way in which you can quickly calculate how many barrels you need to easily heat your greenhouse up for free using the daily shining.

By dividing the number of jugs or gallons by 55, you will end up with a great estimate of how many barrels you need. That’s the common size of a large barrel and the amount you will need to heat up your greenhouse.

Can you use candles to heat a greenhouse?

Answer: The simple answer here is yes.

However, you need to be aware that there has to be some ventilation to get rid of the CO2.

It could just be some gaps in your greenhouse and should not be an issue from a single candle, but it can become a problem if you burn several candles at the same time in your greenhouse to heat it up.

How to heat a greenhouse with a wood stove

You might wonder how you can heat up your greenhouse with alternative methods during the cold winter months and not by doing it with gas or electricity.

A standard wood stove can be an alternative method to heat up your greenhouse and should be adequate to heat most hobby greenhouses.

The disadvantage with a wood stove is the need for constant feeding, which means that the door into the greenhouse more often will be opening and allowing the heat to escape.

However, using a soapstone woodstove in your greenhouse is a better solution than a wood stove, because it will be able to retain heat during night hours when it runs during the evening, so you will not have to do additional burning in the evening.

When it is still cold and freezing outside during day hours, you will still only need to start it burning again in the morning and it will be able to stay warm during the day when you are going to work or just not able to be home.

A better solution if you really want a wood-burning stove to heat your greenhouse, but a more costly option is a wood-burning furnace placed outside the greenhouse. Then you will not lose any heat when the door is opening into your greenhouse and it will also eliminate any risk of carbon monoxide accumulating inside the greenhouse.

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