Good adjustable air flow through the side holes is a durable lightweight ventilation guaranteed. I reach into the greenhouse without heating 24 ° at about 22 ° room temperature, a ventilation slide is just 1cm open. For wall (1 location) and under the greenhouse (2 layers) is corrugated foam sheet (often used as a filler for Ordered) for insulation (temperature I have measured nich before insulation).
In the Second with heating underneath I had already reached 28 ° after about 1 hour. Here a terry dishtowel between greenhouse and heating, so that the heating foil is not damaged by the sharp bottom. Both vent holes almost 0.5cm open and it is only getting cooler by switching off the heating.