[grendel]

imagines 3 tier greenhouse cover rising up and floating off like those fire lantern things - followed by several ufo repports.
Grendel

[Yorkie]

Frankly, the level of insulation on these greenhouses is so poor that I wouldn't waste my time and money in trying to do anything with them.

[Goosegirl]

I have a 4-tier one that sits in my greenhouse. I also bought a fleece cover for it from Wilko and sat it on some polystyrene sheeting, then put the clear cover on, then the fleece one. I also had some fleece sheeting which I threw over it. I used a max-min thermometer and found that the inside was about five degrees warmer than the greenhouse itself. I made sure to open both the zip doors on sunny days to give it an airing. This worked for getting a small but early start to veg plants that will germinate at lower temps like broad beans. For outside use, I would say treat it like a cold frame. Get some thick polystyrene "slabs" and set it on them, put some more slabs on edge around the outside of the bottom edges of the covers like a little wall to prevent the lower colder air getting in there, and secure them with something, then anchor it securely against the wind. You can remove the fleece covers when you need more light. If you really want heat, then make a hot bed of fresh horse manure and straw like the Victorians made, and set it on that. Might whiff a bit though  and may not be suitable for such a small structure as it may cause damping-off due to condensation.

[richie]

imagines 3 tier greenhouse cover rising up and floating off like those fire lantern things - followed by several ufo repports.
Grendel

lolololol brilliant....