By Barbarak
North Yorkshire,
United Kingdom 
I would welcome opinions on whether insulating a greenhouse with bubble wrap actually works to protect pelargoniums and fuschias. I don't have very tender plants to protect, just the above and cuttings. I know it will depend on how cold it gets but how many degrees above the outside temp will the insulation raise the internal temp.
I also have a cold frame which is home to more mature young plants and sweet peas.
Thanks
13 Nov, 2016
Answers
Hmm...maybe it was Garden Smart....
13 Nov, 2016
Hi, I have my greenhouse insulated with bubble wrap, and we have had temps down to minus 2c, but the greenhouse temp was 1c, so near enough to Tugbrethil's figure, Derek.
13 Nov, 2016
Well, that is about 1 1/2 º per layer--the greenhouse itself plus the wrap--so maybe I haven't been all daft. Still haven't found the episode, though.... :/
14 Nov, 2016
Thank you. I'll insulate and hope we don't get prolonged subzero temps
14 Nov, 2016
You might be interested in this discussion from a few years ago
http://www.growsonyou.com/question/show/175236
It also contains another reference which may be worth following up. Not permanent or easy solution but better than nothing on a cold night.
14 Nov, 2016
Large drinking water jugs--of the kind used for office water coolers--spotted about the greenhouse, and filled with water and food coloring, can moderate temperatures in the greenhouse. They absorb light during the day, convert it to heat, and slowly release the heat at night.
14 Nov, 2016
I remember seeing on Growing a Greener World that each layer of air space raises the internal temperature 2º C. I really should check those numbers, though.
13 Nov, 2016