1. Greenhouses: prices, uses, types - what do you need to know?

1.1. Various uses

If you’re thinking about buying a greenhouse, you’ll first need to consider what it’s going to be used for. Different types of greenhouses are used for different purposes. A greenhouse where you can start seedlings off is different from one where you can grow crops and flowers all year round. Some greenhouses trap the heat better, others have a larger useable area, and so on.

1.2. Greenhouse heating

Greenhouses may or may not have heating. Those with heating have a wider range of uses. For example, they can be used for propagation and hibernating as the growing season is extended. They can also be used to bring seeds to the seedling stage before being transplanted outdoors, and, of course, tropical plants won’t succeed without heating.

1.3. Greenhouse size and extending it

If you can, we always recommend you go for a modular greenhouse because it can easily be extended if required. After all, you might find that some years you’ll need more space than others. However, it’s always best to try to calculate and predict exactly how much space you’re going to need before buying and putting up your greenhouse. You should also make sure there is sufficient space for you to move around freely between the benches and shelves. These must be deep enough for the plants, but no more than 60 cm deep and 100 cm wide so you can reach what is on them. Every greenhouse needs an adequately sized potting bench or table, too.

2. Build your own greenhouse or buy a ready-made one?

2.1. Building your own greenhouse

The first thing you need to do is decide whether you want to build your own greenhouse from scratch or to buy a manufactured kit. We recommend you only take on building your own greenhouse as a last resort. A manufactured and professionally installed greenhouse has several advantages. It will certainly be of better quality and will therefore last longer and save you a lot of time and money in the long run. However, if you do try to build your own greenhouse, remember that the bulkier your frame, the less light and heat it will let in. Also, you probably won’t be able to find everything you need in the shops and hardware stores, so you’ll have to be prepared to improvise and make compromises, which will involve even more effort and expense.

2.2. Manufactured greenhouse kits

When you’re buying a manufactured greenhouse kit, we urge you to steer clear of the cheapest ones, which you’ll probably be able to find in garden and home centres. Always go for a more expensive, but better quality one.

Sturdy materials

You need to pay attention to how sturdy the frame of the greenhouse is. It should be made of strong, durable materials that can support up to 100 kg and withstand strong gusts of wind. Our region is prone to sudden changes in the weather and strong winds, so the greenhouse frame must be able to stand firm against such conditions, without being ripped to bits or ending up in the neighbour’s garden. Furthermore, the structure must also be able to withstand the weight of rain, so you’re not forced to spend the night trying drain water off the roof so it doesn’t collapse.

Good ventilation

In addition to being sturdy, it’s crucial that the greenhouse is as well-ventilated as possible. Good ventilation, even if it’s artificial, is very important so as to protect plants from disease or due to the use of chemical substances. Greenhouse ventilation is essential for many reasons. It helps firstly to control humidity and secondly to maintain a balanced temperature within the greenhouse. In smaller greenhouses, even in rainy season, temperatures can reach over 30°C. Opening the door or a small roof window is not enough to reduce the temperature. Good ventilation can sometimes be achieved by opening the sides, although it is very important that these side vents do not run all the way from the roof to the ground. It’s best if the bottom half of the side walls is fixed with the ventilation openings starting about a metre above ground level. Ventilation in the summer is also very important when temperatures are high because without it plants will wither and die.

3. Different types of greenhouses

3.1. Framework materials

The choice of material for the greenhouse frame will depend on what it is to be used for. The appearance of your greenhouse and how easy it is to clean and keep in good condition will also be affected by what the frame is made from. Typically, wood, aluminium or galvanized steel is used for the frame.

Wooden greenhouses

Of these three materials, wood is certainly the best as it provides good insulation and hence retains the heat well. However, it also has some downsides such as its high cost and the fact it is high maintenance.

Aluminium greenhouses

An aluminium frame is lightweight and requires little maintenance. However, aluminium does not retain the heat.

Galvanized steel greenhouses

Galvanized steel frames are the most expensive, but the simplest to put up and also strong enough to hold larger panes of glass. They do require regular maintenance, however.

3.2. Covering materials

Glass panels are best for greenhouses. A special type of glass is used which is thinner and more expensive because it has a coating that helps let light through and aids heat retention. Its drawback is that it cracks and breaks easily.

Plastic panels are less good. They are more expensive, more susceptible to damage, and can become cloudy over time. They also have poor heat retention and become brittle due to constant heating.

Polycarbonate panels are practical because they are shatter-resistant, virtually unbreakable, and a good insulator; however, they are expensive and become discoloured over time and are not fireproof.

4. Where to site your greenhouse

Sun

The first rule when it comes to siting your greenhouse is that it should be in the part of the garden that gets the most sun during the day.

Position

It is also important that the ridge of your greenhouse runs east to west. It will mean that the plants are exposed to warmth and light throughout the whole day.

Leeward

It is best to locate the greenhouse on the leeward side of your house. The airflow will be good for your plants, while you’ll avoid constant wind or any strong gusts, which can damage the greenhouse.

Water

A greenhouse should never be sited at the bottom of a slope or in a depression. Such places can become waterlogged after heavy rain, which can damage the greenhouse as well as the plants inside. For similar reasons, areas with high groundwater are not good for growing plants.

Close to your house

The closer the greenhouse is to your house, the better. This is primarily due to the amount of water needed for watering your plants, which can be a demanding and laborious task. It’s also more practical to have your greenhouse close to the house in winter as you’ll be able to pick fresh herbs, vegetables, and flowers without too much hassle even in bad weather.