Heating Greenhouse: How To Do It

You want to winterize your greenhouse? But you are not yet sure which type of heating is particularly suitable for your greenhouse? Find out here what options you have and for which plants the different greenhouse heaters are suitable in each case.

Greenhouse types by temperature
Since all plants need different temperatures to thrive, there are also different greenhouses with different temperatures. Learn more about the different greenhouse types here.

Cold houses
The cold house is a greenhouse whose temperature is kept at a minimum of 3 to 12 degrees, even in winter. This is perfectly sufficient for many plants. Especially for the wintering of olive trees, palms and hardy bamboo species such a greenhouse is suitable. These plants are hardy and can withstand temperatures around freezing. Nevertheless, they require individual care to survive the winter. Therefore, regardless of summer or winter, they need to be watered sufficiently. However, only enough so that the root ball does not dry up.

Cold houses are considered to be particularly beginner-friendly, as they do not require greenhouse heating and hardly any maintenance work is required over the winter. However, there are a few things you should keep in mind about cold houses as well. In winter, the greenhouse cools down to -5 degrees, which many suitably selected plants can withstand well. In practice, however, it can get much colder in the cold house, if you do not heat. Periods of frost with temperatures in the double-digit minus range are quite possible in cold regions and hard winters, which even the more robust plants do not necessarily tolerate.

For this reason, there are two different forms of a cold house: the unheated cold house and the frost-free cold house. For the unheated cold house, choose plants that are as hardy as possible or take the risk that some plants will die. For the frost-free cold house, you heat minimally – for example, with the help of a frost monitor, which ensures that the temperature does not drop below freezing.

Savings Tip:
If you want to save money, you can put one to three tomb lights in the greenhouse, depending on the size of the greenhouse. These can prevent the temperature from dropping below 0 degrees quickly.

Tip:
You should always keep the cold house closed on frosty days, and ventilate it sometimes during warmer temperatures. This will keep the plants healthy and free from pests.

Temperate greenhouses
With the tempered greenhouse you keep the temperature at +12 to +18 degrees. Thus, it is perfect for growing vegetables all year round. Besides vegetable plants, almost all indoor plants can thrive here. As a result, it provides a home for especially many types of plants.

Saving Tip:
To save on heating costs, you can cover the walls of your greenhouse with bubble wrap.
Warm houses & greenhouses
In a warm house, the temperature is around +18 to +24 degrees Celsius all year round. In such a greenhouse you can also grow demanding plants all year round. Especially tropical plants feel comfortable here, for example banana plants, gardenias, coffee plants, mango and the popular orchids.

All in one: the divided greenhouse
If you value a wide variety of plants, you can also divide your greenhouse into different temperature zones. You can use bubble wrap (bubble wrap) to divide it. Make sure that the film is not colored or opaque.

When dividing the greenhouse, you can proceed as follows: Place the coldest zone “cold house” on the side of the greenhouse away from the sun. The second coldest zone “Temperate greenhouse” is placed on the side facing the sun. The warmest zone “Warm house or greenhouse” is then located in the middle. There, the heat loss is the lowest due to the small external surface. Thus, you have the opportunity to grow in your greenhouse a wide variety of plants with different requirements.

Heating requirement – the value you should know
In order to choose the right greenhouse heating system, you should know the heating demand. This value tells you how much heating power your greenhouse heater needs to provide in order to reach the comfortable temperature for your plants. After all, your plants will only thrive if the greenhouse achieves the right temperature.

The heating requirement can be defined in general terms as the quantity that quantifies the amount of heat energy required to heat a room to a certain temperature. You need various individual data for the calculation, such as the size of the greenhouse, the desired room temperature, the outdoor temperature and the k-value.

The formula for the heat requirement is as follows:

Heating demand (watts) = k-value (heat transfer coefficient as a measure of thermal insulation) * glass area (square meters) * temperature difference between outside and inside (degrees Celsius).

Online configurators can help you with the calculation. At https://www.waerme-plus.de/planungshilfen/berechnung-heizwaermebedarf, for example, you will find a suitable configurator that saves you the trouble of calculating.

All you have to do is enter your data there and the configurator will calculate the heating requirement for you. If you buy a greenhouse heater whose performance is lower than the calculated heating requirement, your plants will not thrive or may even die. You should consult an energy consultant, architect or civil engineer to determine the exact relevant data.

Heating types at a glance

To decide on the right greenhouse heater, there are a few things you should know. Learn below how the different types of greenhouse heaters work and what they are best suited for.

Central heating
If you connect your greenhouse to the central heating system of your house, you will achieve the most cost-effective and at the same time lowest-maintenance greenhouse heating. In this case, the heated hot water reaches the connected radiators in the house and the greenhouse via a suitable and professionally insulated piping system.

Since heating in the house tends to take place during the day and heating your greenhouse tends to take place at night, the heating circuits must be installed separately. This means more effort during installation.

Advantage: The heat is evenly distributed into the greenhouse through the pipes of the heating system. Thus, the greenhouse is heated evenly and the plants are heated gently.

For planning such a heater, it is best to talk to a heating expert.

Individual oil heater
This greenhouse heating system is only worthwhile if you heat your home with oil anyway. Otherwise, you would have to keep a stock of heating oil especially for the oil furnace in the greenhouse. You will also need a suitable flue pipe, as burning oil produces harmful gases that will harm your plants and you.

Gas heating
This greenhouse heating system burns the gas, and the resulting heat is released into the greenhouse. Single gas furnaces convert heat much more efficiently than single oil furnaces, making them about 70% more effective. You can either fill the gas oven with individual gas cylinders or via a gas tank.

Advantages: Hardly any exhaust gases are produced and the level of CO2 in the greenhouse increases. This in turn has a positive effect on the plants, since CO2 is needed for photosynthesis.

Electric heater
If you have already installed a power connection in your greenhouse, the electric heater is well suited. Then you only need to plug the device into the socket suitable for wet rooms and turn it on. Electric heating uses heating coils to convert electricity into heat.

Tip: If you only have a small greenhouse, you should take a look at our greenhouse heaters. You can also pay for these conveniently by installments.

Electronic greenhouse heater

Advantages: Electric heaters produce no exhaust fumes and consume no oxygen. They do not produce pollutants that could affect the growth of your plants.

However, note: household electricity from the wall socket is not very ecological due to its inefficient production method. To generate electricity as ecologically as possible, a solar heating system that you install on the roof of your house or garden shed is a good option.
Solar heating
Do you operate a solar heating system on your roof? Then you can also use it to heat your greenhouse. Such a system will produce enough energy to heat your greenhouse even in winter. With the help of water-filled solar tubes laid inside the greenhouse, the stored heat is released depending on the temperature inside.

Advantages: By generating the solar power ecologically, you not only save money, but also do something for the environment.
Floor heating
In floor heating, hoses or metallic heating pipes are laid in the ground and filled with warm water. You should lay the hoses near your plants.

Advantages: The roots of the plants are supplied with sufficient heat and thus do not die. Also, the heat from the soil is distributed throughout the greenhouse.
Candle heating
Do you not have electricity in your greenhouse and do you not want to heat it with gas? Then your choice could be a kerosene greenhouse heater. This is especially suitable for smaller grow houses, as the power is lower than other variants. However, here you need to keep in mind that you always need to refill the heater manually. The kerosene heater can be operated with kerosene as well as with kerosene.

Caution: Petroleum and kerosene are highly flammable in combination with fire. Therefore, you should fill the kerosene heater only in well-ventilated rooms or outdoors.

Advantages: You can use the candle heater hanging or standing, as its design is very compact, space-saving and flexible. In addition, it does not require electricity or gas connection, easy to install and inexpensive.

Compost heater
A compost heater, also called a biomeiler, naturally generates energy and heat in your greenhouse. In this process, pipes are laid inside the compost material, which are filled with water. As the compost metabolizes, temperatures between 50 and 60 °C are generated.

Advantages: You compost your organic waste and use the resulting heat as greenhouse heating. Thus you kill two birds with one stone.
Earth greenhouse
A so-called earth greenhouse uses the natural heat of the earth as greenhouse heating and thus protects the plants from cold and frost. Such a greenhouse is installed deep in the ground. The depth in the ground protects against particularly cold temperatures in winter and overheating in summer. However, with such a greenhouse you need to find the right place in your garden, it must get plenty of sun and the soil must be free of roots.

Tips for saving heating costs
Are you afraid of too high heating costs for your greenhouse? We’ll show you how you can cut costs with little effort.

Tip 1: Frost monitor function

When buying a greenhouse heater, you should definitely pay attention to the frost monitor function. This turns on the heating only when the temperature falls below the value you set. This way, you can avoid unnecessary heating and save a lot of money.

Tip 2: Insulation of the greenhouse

Make sure that your greenhouse has good and sufficiently thick insulation. This is crucial because it has a great impact on the consumption of greenhouse heating. In this case, the generated heat can be better retained inside the greenhouse.

Tip 3: Optimal location of the greenhouse heater

All plants should be supplied with heat as evenly as possible. That is why it is important to install the heater in the right location. If it is equally warm everywhere in the greenhouse and you only have to switch on the greenhouse heater occasionally, you have found the best location.

Keep the following in mind:

Do not place the heater too close to the plants.
Also, do not place it too close to the entrance
Install as centrally as possible in the greenhouse
Attach additional fan to redistribute warm air
Place thermostat centrally at plant height
Tip 4: Do not set the temperature of the heater too high

The greenhouse heater temperature should be set neither too why nor too cold. Adjust it to suit the plant species. Some plants like it a little warmer, others a little colder. Set only the minimum temperature needed: Every extra degree costs money unnecessarily!

Without heating it does not work
Unless you want a cold house, you can’t avoid a greenhouse heater. If you only have a small greenhouse, you can safely use the inexpensive petroleum heater. Do you have a larger greenhouse? Then, depending on the conditions, a gas heater or an electric heater could be the most affordable option.

If you have already equipped your greenhouse with sockets during the planning stage, it is obvious to opt for an electric heater. It ensures that the oxygen level in the greenhouse is not reduced too much, and you do not have to constantly check whether the fuel is empty.

In any case, when buying your greenhouse heater, keep in mind the power that you need.

Frequently asked questions

Here you will find answers to questions that we are often asked.

Is it possible to heat a greenhouse with the help of candles?

Yes, it is possible – at least if you want to increase the temperature of a cold house a little, candles are suitable.

Place them in small clay pots, as they retain heat longer and release it to the outside or to the plants in the greenhouse.

When do I need to start the greenhouse heater?

If possible, the greenhouse heater should always be in operation – due to the thermostat, it only switches on when the temperature drops too much anyway.

An integrated frost monitor ensures the required minimum temperature in the frost-free cold house.

Is my greenhouse winterproof?

All greenhouses that you have to anchor to the ground with a foundation are winterproof. Foil greenhouses, on the other hand, are only suitable for seasonal use.

Please dismantle the greenhouse’s film before the first frost so that it does not become porous.

When do I need heating for the greenhouse?

If you have a cold house, you do not need a heater.

For any other type of greenhouse, it is advisable to install a heater throughout the year to be able to react at short notice in case of temperature fluctuations.

Is it possible to build and dismantle my greenhouse seasonally?

In principle, this is possible, but it is only recommended for foil greenhouses. All other houses are not designed to be dismantled.

They, like any other piece of furniture, suffer from frequent disassembly and assembly.

What does a frost monitor do for the greenhouse?

A frost monitor automatically controls the heating in the greenhouse. This allows cold-sensitive plants to overwinter in Central Europe without any problems.

As soon as the temperature threatens to drop below freezing, the frost monitor turns up the heating. This function is particularly practical for cold houses.