Net or plastic? Choosing a greenhouse in Namibia

If you want to grow fresh produce here, you will not get around a greenhouse in Namibia. I am not talking about maize, wheat or millet. I am talking about high value horticulture: leafy greens, herbs, tomatoes, the things that actually pay. The sun here is simply too brutal to grow those in the open.

So the question is not whether you need a greenhouse. It is which one. Net or plastic? That decision shapes everything that comes after it: your budget, your workload, your winter, and whether you end up with a productive growing space or an accidental sauna.

The short answer: when in doubt, go net

When someone new to growing asks me what to build, whether for a garden or a first small operation, my standard answer is a net greenhouse with shade net somewhere between 40% and 60%.

Net greenhouses are easy to build. Anyone who does not have two left hands can put one up. There is no ventilation to design, no electricity needed (unless you go hydroponic and need a pump), and far less that can go wrong.

The colour question comes up a lot: white net or green? At garden scale, it barely matters. Nobody with a 10 square metre setup will ever feel the few percent of yield that ride on net colour. Pick the one that looks good, because you are going to look at it every day. At my place I went green on the sides and white on the roof, and it looks really cool. If you are putting up 10 hectares, fine, then the colour is worth agonising over. In your garden, it is an aesthetic choice.

First, put it in the right place

Before we compare the two types, one rule that applies to both: keep your greenhouse away from trees. Trees are unpredictable with light. One month they have leaves, the next they do not, and the sun moves through the seasons while the tree stays put.

To be clear about what “away from trees” means in practice:

• A tree behind the greenhouse, on the shaded side away from the northern sun, is fine. It will never be in the way.
• A tree in front, between your greenhouse and the sun, is a train smash. Do not build there.
• A tree to the side will rob you of either morning or evening sun. If you truly cannot get away from it, place things so the tree blocks the evening sun. That is the least damaging option.

If you cannot afford a greenhouse at all, then yes, growing under a tree is better than nothing. But the moment you invest in a structure, the tree stops being a friend.

Why we don't build glass greenhouses in Namibia

People sometimes ask why we do not build glass houses like the Dutch. The answer is simple: glass earns its keep in cold climates, and we do not have one. We get cold spells, but nothing like Europe or North America. A glass greenhouse costs at least three to four times what a plastic one does, partly for the glass itself and partly because the structure has to be built heavier to carry it. In Namibia that money is almost impossible to justify.

So the real choice here is net versus plastic.

Net vs plastic at a glance

What the net greenhouse gives you, and what it costs you

The big win with a net greenhouse is that you hand control to nature, and nature does a decent job. Ventilation is a solved problem: the wind blows straight through. Heat rarely becomes dangerous. Your plants might look a bit sad at midday in the peak of summer, but everything stays manageable.

That airflow buys you more than comfort. Powdery mildew, which plagues us here especially through the winter months, struggles in a well ventilated space. So do spider mites, which are incredibly difficult to get rid of once they settle in. Summer production in a net house is excellent: lettuce, basil, even watermelons, with no real limitation.

The one big drawback is winter. In central Namibia the nights get properly cold, and a net gives you no protection from that. But I want to push back on the idea that this means “no winter production”. It means being deliberate about what you plant. Lettuce, for example, grows happily through our winter. The growth rate drops a lot, but it grows. Herbs and the more tender crops are limited, so plan around them.

Lettuce matters to us for a bigger reason too: it is one of those crops Namibia should not be trucking 1,500 km up from South Africa when we can grow it here ourselves.

One summer quirk while we are at it: iceberg lettuce planted in the heat will not form a head. Instead of a tight round ball you get a wide open thing with gigantic leaves, less lettuce, more open cupboard. Too much warmth does that. Choose your varieties by season.

Farming seriously? Go plastic

If you are a farmer and you want to get serious about fresh produce, I will not tell you to build a net greenhouse. Get a plastic one.

The reason is production. At scale, 20% more production can be the difference between a profitable operation and a failing one. Even 5% matters. In a 10 square metre garden setup you will never feel that difference; your plants will simply look great. On a commercial block you will feel it in your bank account, so you optimise for it.

The trade-off is that everything nature did for you in the net house is now your job. You are in charge of the wind, so you need circulation fans, which cost money and need electricity. You are in charge of temperature and humidity too. That means either a lot more of your time or a lot more money in automation. How much to automate and how much to simply do by hand is a discussion for another post, if there is interest.

Control also creates a new need: knowing what is actually happening in there. In a net house, monitoring is nice to have. In a plastic house, it is how you learn. Once you can compare the data, you start seeing things like: if I open up at 5:00 in the morning instead of 7:00, my lettuce puts on more weight. The professionals track all of this against vapour pressure deficit, or VPD. Relative humidity will do fine until you go professional.

Sheeting is where people get burnt

With a net house, the sheeting decision is shade percentage and colour. With a plastic house, the sheeting decision is the whole game, because our number one enemy, the sun, attacks on two fronts: it cooks the air inside, and it slowly destroys the plastic itself.

Three rules:

• Never go below 200 micron. Not worth the risk. 200 or above, always.
• Look at the light figures. Good film is sold on two numbers: light transmission, how much light comes through, and diffusion, how much of that light gets scattered on the way. Diffused light is the good light. It reaches deep into the canopy, spreads evenly and does not scorch. Harsh direct light is the bad light. For our sun, go for a high diffusion film with transmission somewhere around 85 to 90%.
• Buy from a reputable source. Decent film lasts around five years in our sun. The cheap imported sheeting you find in discount shops is not greenhouse film, and the shortcut bites you twice: less production now, and a new cover after two years. We supply greenhouse sheeting as part of our greenhouse services, so contact us if you need it. It does not have to come from us, but it does have to come from somewhere reputable.

Keeping the heat out

Heat management in a closed greenhouse deserves its own post, and it will get one. But since an unmanaged plastic greenhouse in Namibia is quite literally a sauna (skip the wooden box, save your money), here is the short version.

Passive first. Natural ventilation through roll-up sides and roof vents, the openings along the ridge, gets you a long way. You can start cheap with manual roll-up sides and upgrade later to sensors and controllers that open things automatically. People label these “low-tech” and “high-tech” greenhouses, with a mid-range in between that nobody can define. I find the labels overrated. Manual sides are low-tech, a Dutch-style automated house is high-tech, and everything here sits somewhere in the middle. A bonus of roll-up sides: when the power goes out and your fans stop, you can still get air moving.

Then active cooling. The proven system is the wet wall: extraction fans pull air through a wet pad wall and the evaporation strips the heat out. Traditional pads are cellulose, essentially treated paper, and last about five years. The newer plastic pads claim eight to ten. You need power for this, so if you are on the grid, run it and pay the bill gladly.

Evaporative cooling is particularly well suited to Namibia because our heat is the nice kind: dry. Evaporation works brilliantly in dry air, and the moisture it adds is usually welcome in our climate. In humid places the maths flips. This matters in the subtropical north of the country: pushing more moisture into an already humid greenhouse invites fungal trouble like leaf spot, so think carefully before adding evaporative cooling there.

Misting: emergency only. You can buy misting systems cheaply and they work amazingly, until they don't. Our borehole water is full of lime, the nozzles clog fast, and then the system drips on your plants, which your tomatoes will hate. Keep one as a last resort for the 20 or 30 days a year when nothing else copes. As a daily solution, I really do not like it.

The one takeaway

Match the greenhouse to your ambition. Growing for your household or starting small: build a net greenhouse, 40 to 60% shade, away from the trees, in a colour you enjoy looking at. Farming fresh produce for a living: build plastic, 200 micron or better, high diffusion film from a reputable supplier, and plan your cooling before you plant a single seedling.

Get that decision right and everything else in Namibian growing gets easier.

Need greenhouse sheeting or advice on a setup? Contact us. New to growing altogether? The Hydroponics Bootcamp is where to start.

Further reading

• Best Hydroponic Kits for Beginners: 2026 Buyer's Guide
• Installing the Bluelab Pro Controller