Depending on the plants you want to cultivate or keep over the winter in your greenhouse – you may or may not need to consider using greenhouse heaters. If you do decide to install greenhouse heaters remember that their primary function is to prevent the temperature dropping below freezing point, regardless of the plants in the greenhouse. Then, secondly, you might need to set your greenhouse heaters to maintain a higher minimum temperature – if you have some particularly delicate plants in the greenhouse.
Typical Greenhouse Temperatures
There is absolutely no point at all in installing a greenhouse heater if you then let the temperature drop below freezing. To do this you will need your greenhouse heaters to be operating before freezing point is reached and so most gardeners will set their greenhouse thermostats to around 6 degrees C (43 F), which is quite sufficient to protect most plants.
Please bear in mind that if you set your thermostat to 10oC, 50oF, you will double the fuel bill and setting the thermostat to 16 degrees C, 61 o F, will quadruple it! Should you need to maintain a higher temperature than 16 C you can probably save money in the long run by installing ‘under soil’ heating. This will act as a cozy blanket for your plants and you won’t be heating air unnecessarily.
Electric Heating for Greenhouses
Although the most expensive method for greenhouse heating – it is also the best method. Clean and reliable it doesn’t, in itself, create moisture in the greenhouse due to a fuel burning. The very fact that the greenhouse heating is electrical means you don’t have to pay for a cable to be run to the greenhouse to power the thermostats and you don’t have to check that the fuel level in a burner is low.
In other words, when it’s cold, raining or snowing – you don’t have to constantly be going out to the greenhouse to check that it is working OK. Any electrical installation for a greenhouse should be carried out by a properly qualified electrician and be regularly inspected and serviced.
Oil Heaters for a Greenhouse
This usually means having kerosene heaters in your greenhouse, which will be a very cheap option for heating a greenhouse. However, oil heaters bring with them several problems. First you will need to regularly replenish the oil supply in the heater, secondly they produce a lot of water vapor when the oil burns and thirdly, to deal with the excess water vapor, you need to leave some ventilation open – meaning the warmth you’ve created can escape. Two other annoying things with oil heaters are- having to check that the wick is burning correctly about 10 minutes after lighting it and you’ll need to regularly clean the burner parts.
Solid Fuel Heaters
The traditional way to heat a greenhouse was always with a solid fuel burner, typically wood or coal, heating water in 4 inch pipes. Modern solid fuel greenhouse heaters can be fitted to heat water in pipes or as an air heater; they can also be fitted with thermostats.
Cheaper to run than electric heaters but less demanding on your time than oil heaters, solid fuel greenhouse heaters are still a popular choice. Unlike an oil heater, a solid fuel heater will always require a chimney. Whilst that might add slightly to its overall cost, it does mean that any water vapor produced as a result of burning the fuel is vented, without having to leave a ventilation slot open inside the greenhouse.