Do you need heating in a Mediterranean greenhouse?

Not to keep the crop from freezing, but yes to keep it dry. A minimum pipe temperature is what drives air movement and lets moisture leave the crop on a cold night; without it the house cools to dew point and condensation settles on the leaves.

Why do unheated Mediterranean greenhouses lose crops in winter?

Unheated is not the same as uncontrolled. On a clear January night the house radiates heat to the sky, the air reaches dew point, and free water on the leaf is what fungal disease needs. The loss shows up as disease rather than as cold damage.

Is a plastic tunnel enough in this climate?

It is what much of the region uses, and it is why so much of the region fights the same winter problems. A closed, controllable structure costs more and removes the condensation cycle that limits the unheated alternative.

What makes the Mediterranean summer manageable?

Low humidity. Dry air means evaporative methods and ventilation both work well, so summer is a solvable problem in this zone in a way it is not in the humid tropics.

Mediterranean — DutchGreenhouses

Unheated is not the same as uncontrolled

Where: southern Spain, Italy, Greece, Turkey, Morocco, Tunisia, Israel, coastal California, central Chile, parts of South Africa and southern Australia.

The climate that produced Almería

Winters are mild enough that crops survive without heat, summers are hot but dry, and radiation is generous almost all year.

That combination built one of the largest concentrations of protected cultivation on earth, mostly in low-cost plastic structures with minimal control. It works, at a level, and it is the reason the region exports enormous volumes of vegetables in winter.

So the honest starting point is that a cheap house here does produce a crop. The question is what it gives up.

What the cheap house gives up

A mild winter night in a poorly controlled structure is a humid one. The crop transpires, the temperature falls, the air reaches saturation, and moisture condenses on leaves and fruit.

That is the whole disease equation — and it is why unheated Mediterranean production runs so much higher crop-protection pressure than a heated house at the same latitude. A minimum pipe running at low output is not there to keep the crop warm. It is there to keep the air moving and the moisture off.

Unheated is not the same as uncontrolled, and the difference between those two is where the margin lives.

Summer is a shading and ventilation problem

Radiation is the surplus here, not the shortage. So the screen package leans to shade and diffusion, and roof vent area matters more than insulation.

Evaporative cooling works well because the summer air is dry — the same physics as the desert, without the same water scarcity, though water is tightening across the whole region and that is worth planning for now rather than later.

The commercial question this climate really asks

The gap between a plastic tunnel and a controlled glasshouse here is not survival. It is yield per square metre, product quality, and whether you can supply a supermarket on a date.

That makes Mediterranean projects an unusually clear investment conversation: what does the next level of control return, at what capital cost, in your market.

DutchGreenhouses® builds the high-control end of this climate. Get in touch and we will put numbers against the step up.

From the knowledge base