How to maintain the temperature in a greenhouse

A greenhouse can help you cultivate out-of-season fruits and vegetables, or even exotic ones that would not be able to grow in the weather where you intend to construct the greenhouse. A large part of this is down to the temperature of the area. Let us look at how you can control the temperature of the greenhouse for the optimum yield of your crops.

Maintaining the right temperature for the greenhouse can be divided into two distinct things: one is how to keep the greenhouse cool in summers when it can get too hot, and the other is keeping it warm in the winter when temperatures dip too far.

How to track temperature in the greenhouse

how to maintain temperature in greenhouse
Greenhouse Thermometer

An often overlooked aspect of maintaining greenhouse temperature is the ability to track the temperature of the greenhouse. A thermometer that can show you the minimum and maximum temperature of the last day or so is a great tool to have, so you know what the temperature extremes are in the greenhouse.

More advanced thermometers with alarms and remote monitoring are also available. If the thermometer has the ability to show you the humidity as well, so much the better, since temperature and humidity are interlinked.

A top-of-the-line ‘smart’ monitoring system will offer the ability to connect vents, fans and heating appliances to the thermometer and automatically keep the temperature at an optimum level.

How to keep your greenhouse warm during the winter

Heating mats are a good solution to keep your greenhouse plants warm during the cold times – they are installed in the floor, thus giving diffused heat to the plant roots, and stimulating beneficial microbial growth in the soil as well.

Another method of heating a greenhouse is to use a boiler and piping throughout the greenhouse, like heating in your house. Water is heated in the boiler and the hot water is piped through the greenhouse, heating it up as it goes along. This type of greenhouse heating is called radiant heating.

Using electric heaters is also an option, although not a very efficient one – you’ll need to monitor the greenhouse temperature because the temperature will drop once you shut the heaters off.

how to maintain temperature in greenhouse
Electric heater

If you want to make good use of natural heat, you can keep barrels of water along the walls of the greenhouse. They can be made out of plastic or steel, but they need to be painted black. You can add black food coloring to the water to help it absorb heat better. They will heat up with the sunlight during the day, and give their absorbed heat back out during the night, thus maintaining the temperature.

Bubble wrap is very handy to keep heat in – you can use it wrapped around the plants themselves, or to cover the walls of the greenhouse. Try and get the bubble wrap at a plant specialty store, as this bubble wrap isn’t the same as regular bubble wrap, but in an emergency the regular one will do as well.

Moving your compost into the greenhouse will offer many benefits – the compost is exposed to a warmer area, which makes it break down faster, and it gives off heat as it breaks down, contributing to the greenhouse heat. This is a good thing no matter which way you look at it, because you get heat, and your compost gets ready earlier than it would outside, in winter. The ideal place for the compost is in the centre of the greenhouse.

Another really simple solution is to keep the plants off the cold ground – upside down trays on which the pots are kept, or a layer of pebbles at the bottom of each pot will work as insulation from the cold in the ground.

A very important thing to remember is to ventilate your greenhouse on sunny winter days, so that there isn’t too much buildup of moisture and carbon dioxide, which can lead to fungal growths in the greenhouse.

How to keep your greenhouse cool during the summer

You can broadly divide greenhouse cooling methods into two types, those that need electricity, and those that don’t.

Vents are a simple solution to cool the greenhouse. Placed on the roof, they will let rising hot air out. Placed on the sides of the greenhouse, they will let air through. Try and place wall vents in the direction of the prevailing wind, with the intake vents low down and the exhaust vents high up on the walls.

How to maintain temperature inside greenhouse
Shade cloth

You can also couple roof vents with walls that fold up out of the way when it is too hot. If you prefer walls made out of rigid materials, you can have them made with windows or panels that open some way. If the walls are rigid and without openings (or have the openings shut), you can either cool the walls by spraying water on them or use a shade cloth to keep the heat down.

Shade cloths are far more effective on the outside of a greenhouse, but you also need to be careful to not block too much sunlight, or pollination agents from getting through it.

Misting systems also can help keep the temperature down while keeping the humidity high.

Sometimes the simplest solutions are the best ones: construct your greenhouse in the midst of deciduous tree cover. This will ensure it gets enough light and heat during winter, and enough natural shade during the summer to keep its temperature even throughout the year

If you choose to use electricity, your options open up. We’ve already talked about vents – if you add fans to wall vents, you can control the airflow through the greenhouse. You can use solar powered fans to help reduce the dependency on electricity.

It is important to remember that there is no standard solution for all greenhouses, the best solution for your greenhouse depends on its location and the type of crop you are growing. A little research on the best solution for your greenhouse’s area will have you increasing your yield in no time.

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