Hi Jes, in the UK 'cold greenhouse' means no heating and, to Alpine growers, lots of ventilation. So all the plants get is protection from rain. In Winter it is almost as cold inside as it is outside (but it is dry). In Summer the ventilation, and shading, become all important to stop the temperature inside getting too high.
Of course, like all language, the term is used differently by different people depending on what they grow.
Growers of summer bedding plants or vegetables like Tomatoes would use a heater in April and May to prevent frost damage to their tender plants but still call it a cold greenhouse.
Some bulb growers will have a soil warming cable in their sand plunges to prevent the bulbs and roots being frozen and damaged in very cold weather but they too would still call it a cold greenhouse.
If only life, and language, were simple
