Growing plants in a greenhouse throughout the year is very rewarding but also quite difficult, as the colder months see temperatures drop, even in well-insulated structures like a greenhouse.
If temperatures drop below a certain point then many plants and vegetables will struggle to survive the cold snap, which is understandably frustrating for gardeners putting the time and effort to grow these plants over the year.
So, what exactly can you do to ensure exotic plants and vegetables survive the colder months in your greenhouse? One increasingly popular option is to invest in a quality greenhouse heater!
Greenhouse heaters are simple yet effective way of maintaining optimal growing temperatures inside of a greenhouse when temperatures drop.
While many plants are hardy enough to survive temperatures close to 0°C, many require a minimum of 10°C for healthy growth, but this can be hard to maintain without auxiliary support in the shape of a heating system.
Many types of heaters are available for this, including electric fan heaters, paraffin heaters, and tubular heaters. These can be quickly installed and will let you easily manage the inside temperature of the greenhouse to ensure maximum growth during winter. The best greenhouse heaters will depend on the area you need to cover. Below we cover some of the top choices available.
The Bio Green Phoenix is one of the best electric fan heaters for greenhouses. This robust heater will efficiently warm spaces up to 100sqft and prevent frost from developing in areas up to 180sqft, giving you the perfect growing conditions during the cold winter months.
Better still, because it’s a fan heater combo it can double up as a cooling fan, meaning you’ll get plenty of use from it during the warm summer months.
There are three heating outputs available including 1kW, 1.8kW, and 2.8kW, so you can adjust these each day according to the changing temperatures. This makes it easy to maintain an ideal temperature throughout winter, where some days can be colder than others.
The fan function can be used alongside the heater to improve air circulation, which is great for avoiding cold spots and reducing mould and fungal growth on plants. You can suspend it from the roof of the greenhouse or have it freestanding, with the latter being useful for plastic greenhouses.
A built-in thermostat can also be programmed so that the heater turns off once the desired temperature is reached, helping to save energy while maintaining the optimal conditions.
Its stainless-steel housing also comes with a waterproof IPX4 rating, ensuring the internal components are adequately protected from any moisture developing in the greenhouse. Many owners say that it is one of the best greenhouse heaters for the money.
Bio Green PAL 2.0
If you want the reliable functionality of a Bio Green electric fan heater but feel your greenhouse is too small for such a robust heating system, consider the Bio Green Palma, the smaller model of the Phoenix mentioned above.
Suitable for small and medium sized greenhouses, the Palma comes with a single 2kW heating output that heats areas up to 89sqft. The fan function can be used alongside the heater for optimal airflow at 163 cubic metres per hour, helping to prevent dampness and mould developing inside.
As a smaller device, it can only be used freestanding, although a 1.9m cable means it is easy to position to get the best heat output for your greenhouse. Temperatures can be set to various outputs, ranging from 0-85°, and you have the choice for static or ventilated, the latter turning on the fan for air circulation.
The range of temperature options is impressive for a smaller heater, as many in this size range tend to have just a few settings, highlighting the great quality of Bio Green heating systems.
Like all Bio Green electric fans, the Palma comes with a robust steel housing that has an IPX4 rating, making it splash-proof and protecting the internal components from moisture damage.
2kW Greenhouse fan heater
This 2kW greenhouse fan heater from Simplicity is another solid greenhouse heating solution available for a great price. A rugged heater fan combo, it can be used to increase temperatures during the winter and cool things down during the summer months, working in spaces up to 8 ft x 12 ft, so if you have larger greenhouse this is a good choice of heater.
While there is no internal thermostat it is compatible with a range of third-party devices, so simply connect a thermostat for comprehensive temperature control. It has a decent range of temperature settings and the device will turn off if the desired setting is reached, ensuring the greenhouse never gets too warm or cold.
It’s one of the more powerful heaters you can buy in this price range, with an impressive 2kW output providing enough heat to keep the greenhouse warm even when outside temperatures approach -10°, so it’s a great heater to have when those severe cold snaps set in over the winter.
Moreover, if the main purpose of the heater is to avoid frost developing inside, you can probably use it an even larger greenhouse. Just bear in mind going above the recommended 12 x 8ft will only prevent frost and may not keep the inside warm.
It also comes with an IPX4 rating, making it splash proof and suitable for humid spaces.
LightHouse 135W Eco Heat Greenhouse Heater
One major setback of using a greenhouse heater is that it can increase your energy consumption, leading to higher bills that may feel negates the benefits of being able to grow plants in the winter.
However, if you select an energy efficient heater such as this tubular greenhouse heater from LightHouse then you can enjoy a warm greenhouse without high energy bills.
Available in a range of outputs, the 135W model is the largest available and will warm small and medium sized greenhouses. If you own a larger greenhouse then you can consider buying a few of the tube heaters, as they don’t cost too much and use very little energy.
You can easily connect it to a thermostat for automatic programming, such as staying off during the daytime and only turning on at night. A lack of temperature control function does mean the heater can overheat, although it’s very reliable and unlikely to catch fire – just avoid keeping it near flammables just to be safe!
Even without temperature control, this small heater is very effective at keeping out the cold. It can easily maintain temperatures above freezing, so you never need to worry about frost developing. The use of radiant heating ensures very efficient heat distribution, with the heat going directly to the plant rather than filling the air.
Biogreen WM-P4 Paraffin Heater
The Bio Green WM-P4 is a great alternative to an electric fan greenhouse heater, using paraffin fuel rather than electricity. This means you don’t need to worry about installing power outlets into the greenhouse, with the heater featuring a large 4.5 litres of fuel.
Providing around 16-hours of continuous heat, you can change the temperature output by selecting one or two burners, the latter providing maximum output for those extra cold nights. It’s recommended that you buy a thermostat to use with this, otherwise you need to turn these off manually, which isn’t much use when heating late into the night.
Bear in mind that due to the Co2 emissions the heater produces that it cannot be used inside the house – keep it exclusively in the greenhouse. While the emissions may sound off putting, it actually encourages healthier growth in the plants!
Also, because you aren’t using electricity there is no increased energy bills to worry about. Replacement paraffin is quite cheap as well, so you probably save more money compared to using an electrical heater.
It’s a stable heater that can be placed anywhere on the ground or on a shelf, while you can easily move it around the greenhouse to get the best position for optimal heat output.
Tooltime 2ft Portable Electric Tubular Greenhouse Heater
This portable electric tubular heater from Tooltime is another energy-efficient heating solution that keeps the greenhouse warm and energy bills low.
Measuring 2ft in length, the 30W heater is suitable for smaller greenhouses, although you can combine a few of the heaters for larger spaces too. It comes with wall brackets but you can install it on the floor as well, with the compact design taking very little space in the greenhouse.
The power cable is a decent length at 1.3m, so you should find it easy enough to install anywhere you want.
You will need a time switch or thermostat to set on and off times, otherwise you will need to do this manually or let it run all night, both of which are a bit of a nuisance. However, the heater costs very little so you won’t find it that expensive to add a thermostat or time switch.
It comes with an IP55 splash proof rating, making it suitable for moist environments inside the greenhouse, while it comes with an attractive seamless steel body with a white enamel finish.
How to Heat a Greenhouse During Winter
Looking to heat a greenhouse during the winter months? There are many things that you can do to achieve this, many of which don’t require the use of a heater!
Install a Heating System
As mentioned, one of the best ways to warm a greenhouse during winter is by installing a heating system designed for such conditions. There are a few options available, although it’s widely considered that an electric fan heater is the best choice for most UK greenhouses.
Electric fan heaters combine both a heater and fan function, so not only can you heat the inside of the greenhouse but circulate the air throughout the space.
This is great because it ensures no cold spots develop inside, which can cause mould and fungus to develop. Cold spots often occur around the corners when using a different heating system, which is why fan heaters are a great option.
Reposition the Greenhouse
During winter the sun helps to keep the greenhouse warm enough for plants to survive yet there is less daylight available, so try to position it somewhere outside where it gets maximum exposure to sun throughout the shorter days.
You want either the front or back of the greenhouse to always be facing south for maximum exposure! Of course, this is only possible with portable greenhouses. If you are installing one soon, then make sure that the largest part of the greenhouse faces south.
Poor insulation is the reason for most of the heat loss greenhouses face in the winter, so there are a few DIY tricks you can try to improve insulation.
For example, you could add a layer of bubble wrap inside of a small greenhouse to add extra insulation. Try clipping it on using clothes pegs, focusing on any gaps and lose panes.
Also, using a sealant may offer a long-term insulation boost. There are often gaps around panes, the vent, and the door where air escapes, so try sealing over these to improve the insulation. Look for cracks too and replace any broken panes that can’t be sealed properly.
Another trick for glass greenhouses is to erect a smaller plastic greenhouse inside during the winter, effectively doubling the insulation. You may need to grow fewer plants though!
Add a Water-Filled Container
Filling a container with water and placing it inside of the greenhouse can help to keep it warm during the colder months due to a process known as thermal mass. Basically, the water absorbs heat energy during the day and then releases it at night, helping to maintain temperatures with very little effort.
Try to use a black container if possible, as this ensures maximum heat absorption during the day. You will probably need to use a few containers throughout the greenhouse, filling each one with around 3L of water.
Keeping a pile of composting material inside of the greenhouse can also help keep it warm during the winter! This also helps to create better compost as the material stays dry and doesn’t lose any nutrients like if its left outside in the rain, plus you’ll have some natural fertilizer for your plants once it all breaks down!
Last update on 2023-12-04 / Affiliate links / Images from Amazon Product Advertising API