heating a greenhouse in winter

How Do You Heat A Greenhouse In The Winter?

In Temperature by Ana M

We all don’t like to spend money and energy, or both.

However, sometimes the temperature swings make it hard to maintain the optimal temperature in the greenhouse. Especially during the winter. So, how do you heat a greenhouse in the winter?

I came up with 11 tips and tricks which can help you to make the most of greenhouse without wasting tons of cash on heating.

Tip №1 – Insulate a greenhouse for winter

Let’s start with the term insulation. It is used to describe the process of minimization of heat loss between the objects of different temperatures.

So, the products which have insulation properties are used to reduce the heat loss because they form a barrier between the areas of contrast temperatures.

insulate a greenhouse with bubble wrap

The cheapest and effective product which you can use in your greenhouse is a bubble wrap. To learn more on how to master the greenhouse insulation go to this article.

Tip № 2 – Use Greenhouse Heating Systems

While commercial greenhouses utilize central heating systems and infrared heating, hobby greenhouse can be heated with air circulation fan heaters.

There are three types of heaters commonly used for greenhouses: electric heaters, paraffin heaters and gas heaters.

Electric greenhouse heaters

Electric heaters well known as fan heaters are very convenient if you have a lean-to structure which is attached to your house or the power supply inside your greenhouse.

greenhouse electric heater

You can just plug it in, warm your greenhouse to the optimal temperature and then turn it off.

Paraffin Greenhouse Heaters

If you have a freestanding greenhouse and don’t have an access to the electricity, a paraffin heater is a good option. This is a relatively cheap in comparison to other heaters.

Also, you will have to fill them up with the paraffin oil and re-light them daily.

Gas Greenhouse Heaters

And the last option is a gas heater. Again it is a good alternative if you don’t have a power supply in your greenhouse.

The propane gas is mostly used in the greenhouses because butane tends to freeze in the cold surrounding. When burning it is releasing a beneficial for plants CO2.

If you are unsure which heater to get I am discussing the pros and cons of each option in the ‘Different types of greenhouse heaters’ article.

Tip № 3 – Use day nigh thermostat for greenhouse

So, when you decided that you need a heater in your greenhouse, you want to use it efficiently. To do that you need to use a thermostat. It is a device which switches the heater on and off when needed.

Thermostat senses the air temperature and switches the heater on when it falls down the set temp and alternatively switches it off once it gets too hot.

Today, the majority of heating systems come with a built-in thermostats. So, when you are choosing a heater opt for the option with thermostat.

Tip № 4 – Use a thermometer in a greenhouse

It doesn’t matter whether you have a heater with thermostat or not, a thermometer is a must have in any greenhouse.

greenhouse thermometer

Now, you can find lots of options where you get the hourly temperature updates to your phone. But to start with you can just use a min/max one. To find which thermometer is the best for a greenhouse go to this article.

Tip № 5 – Find an ideal temperature for greenhouse

This is probably the most crucial step. Assess what are you growing, which temperature does it require? For example, when growing tomatoes you need a quite cool temperature and not a humid climate.

However, with the cucumbers you need to make sure that the climate is moist, warm and damp. So, you might be wondering how to keep the optimal temperature for all plants?

Well, ideally you would have to grow tomatoes and cucumbers separately. Which means in two greenhouse. Stop, what if I can’t afford it?! I know, I have asked myself the same question.

So, I would recommend to grow the plants with the same growing requirements together.

What temperature should a greenhouse be in winter?

The temperature in the greenhouse should not be lower than 80-85 degrees F which is equivalent to 27-30 degrees C.

The plants like citrus trees and pelargoniums need a temperature of only 45 degrees F which is 7 degrees C. However, if you have different plants inside your greenhouse you need to separate the area you want to heat.

To keep the greenhouse frost free the temperature has to be 2°C or above

Tip № 6 – Organize the area you want to heat

This is probably the most cost-effective tip. Instead of heating up and insulating the whole structure plan ahead which parts of the greenhouse you actually need to heat.

Let’s use the same tomatoes and cucumbers example. You can separate the area where you grow cucumbers from tomatoes with the curtain made of bubble wrap.

That way you can provide the perfect growing conditions for different plants and keep heating expenses to a minimum.

how do you heat a greenhouse in the winter

Source: Gardener’s World

Tip № 7  – Use a greenhouse propagator

It is always a good idea to use a propagator to germinate your seeds. The prices range from 20-50$ which depends on the capacity of the tray.

I would say that a tray with 72 cells is enough for an amateur gardener. By using a propagator you can definitely save money on heating the whole structure.

Also, there is another option to take care of the germinating seeds which I am discussing in the next tip.

Tip № 8 – Use soil heating cables for a greenhouse

I would highly recommend using soil warming cables together with other greenhouse heating tools to make sure the soil temperature is perfect for propagation.

In a meantime a heater and general insulation will maintain the lower base temperature. The price of the soil warming cables is a little bit higher in comparison to the propagator.

However, these do cover larger area and contribute to the heating of the whole greenhouse. Remember, that you will need some sort of the propagation bed to use the soil warming cables.

Take a note that both soil warming cables and propagator are electric which means that you need to have access to the power supply. So, which option is the best for me?

If you are good at DIY I would go for the soil warming cables and propagation bed. However, if you don’t want to spend time on that an automated propagator is a good buy.

Also, it is a good option to take propagation indoors. That way you don’t need to worry about heating your greenhouse that much. This is called a windowsill greenhouse.

There are tons of commercial options available in different price ranges. However, I found this amazing DIY project of the windowsill greenhouse. If you had a go, please let me know in the comments how it went 🙂

How do you heat a greenhouse soil?

You can use these options to warm the greenhouse soil:

  • Hot air soil heating
  • How water soil heating
  • Heating Mats
  • Soil warming cables

Tip № 9 – Ventilate a greenhouse

Ventilation plays a very important role in the heating of the greenhouse. When you are heating your greenhouse with a heater it contributes to the higher humidity levels.

This leads to the spread of fungal diseases. To avoid it you need to ventilate your greenhouse. The best time to open the vents in winter is on a sunny morning.

Greenhouse Ventilation In Winter

Then, close them just before the sun goes down to keep the daytime heat maintaining your greenhouse warm for longer. To get rid of the excess moisture you need to water your plants sparingly.

You can find more information on how to ventilate a greenhouse in winter here.

Tip № 10 – Use a fleece at night time

You have been heating your greenhouse throughout the day and on the next morning it is cold again? Familiar situation, isn’t it?

So, to trap the warmth inside your greenhouse and save money on fuel you need to think about insulating your greenhouse at nights.

You can use a fleece and crop covers to cover the tender plants in the unheated greenhouse.

Tip № 11 – Alternative ways of heating a greenhouse

I have found some interesting ideas of how on heating a greenhouse in winter without spending any cash on fuel!

The first method is to set up a bucket in the middle of the greenhouse with a compost in it. The breakdown of compost actually releases energy in a form of heat!

Second option is to paint the plastic gallons black and place them where they will get the most sunlight. The larger the gallon, the more heat will be retained!

These are my go-to tips to heating a greenhouse in winter and I hope you will find them helpful 😉 If you have any questions, suggestions or want to share your experience please do so in the comments sections down below.

Happy growing!

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