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Greenhouse Heating – A Need to Know Guide

Greenhouse heating illustratedWithout the proper greenhouse heating system your plants could experience uncomfortable levels of low temperatures that might be harmful to them. Plants require the optimum temperature to stay healthy. Temperatures can vary a lot during the daytime and especially during the night. When investing in a greenhouse heater, a few things have to be taken into consideration. Factors such as cost, type and your unique requirements come into play.

Let’s have a look at the different types of greenhouse heaters.


Paraffin Greenhouse Heaters: The most basic type available that needs consistent trimming of the wick and refilling. Additional ventilation would be required since the fuel needed to run this heater produces fumes. A great emergency backup system for frost that is low in cost.

Gas Greenhouse Heaters: High maintenance heaters that require safety measures and constant monitoring. Gas heaters are generally less efficient that electric heaters. They can be cheaper to run though. Ventilation will also be a pre-requisite since combustion is involved.

Electric Greenhouse Heaters: Though they tend to be more expensive to run, electric heaters generally have more benefits. Not only can temperatures be controlled more accurately without any fumes, additional ventilation will also not be required.

Where to mount the greenhouse heating?

  • free-standing-greenhouse-heaterFree Standing Heaters: No need for mountings since the heater will normally have its own stand. The advantage is that you can place this type of greenhouse heater anywhere in your greenhouse. Unfortunately they tend to take up a lot of space.
  • Hanging Heaters: The most convenient location for a greenhouse heater since they hang from the ceiling and, as a result, take up less space. Tip – Make sure to hang them high enough where possible as not to be in the way.
  • Wall Mounted Heaters: Although these type of heaters do not take up a lot of space, they will need the area in front of them to be cleared. Mounted directly on the wall, they vent to the outside of the greenhouse.

Types of Greenhouse Heater Vents

  • Power Vented Heater: With this type of greenhouse heater comes a pipe and a blower that forces air to the outside of the greenhouse. You can arrange the vents horizontally or vertically. Since the pipes are normally a bit smaller it makes them more efficient.
  • Gravity Assisted Venting: This type of heater makes use of the concept that hot air is lighter than cold air and will rise upwards. It is quite obvious then that the pipes should be placed in a vertical position. Outside air will then have to replace the air that is expelled in this way.
  • direct-venting-greenhouse-heater

    Direct Venting: You will only find this type of venting technique in the sealed combustion types. The inlet and exhaust pipes are inside the other and this controls the flow of air needed. It will only intake the same amount of air that it expels. As a result there is no need to bring in air from the outside.

  • Unvented Greenhouse Heaters: Only to be used in emergencies of a temporary nature (normally paraffin heaters). All gasses are released into the greenhouse and can cause damage to the more sensitive plants if left unchecked.

Greenhouse Heater Combustion

  • Separated Combustion: This type of combustion is associated with the gas greenhouse heater. Combustion comes from using air that comes from the outside. A sealed burner traps the air from the outside using an exhaust pipe.
  • Sealed Combustion: Similar to the separated combustion type, the burner is sealed outside and does not use any air from inside the greenhouse. Direct venting is used for the intake and exhaust of air.
  • Open Combustion: The burner is not sealed and it freely makes use of the air inside the greenhouse. Do not place any flammable liquids in close proximity to this type of heater. In order to properly function, this type of heater should have access to uncontaminated air.

The output range of your greenhouse heater is also an important factor to consider. You should be able to measure the heat output. Calculating the amount of heat output can be tricky and you can always ask your nearest greenhouse store staff for tips. A great online resource for calculating your greenhouse heating output

With so many greenhouse heaters to choose from it can be a bit overwhelming. You should take the heating element into consideration when doing your greenhouse plans. If you have an existing greenhouse, then you will have to make an accurate assessment of its needs before buying a heater. A lot will depend on the area that you live in, the size and height of your greenhouse and your budget.

Happy Greenhouse Growing!