This is my first posting/question. Hello to all. I'm hoping someone(s) can offer some feedback on my plan to use bubble wrap as insulation in my greenhouse.

I have a 24' Rion greenhouse (polycarbonate siding). It is unheated. In the past I've waited until the temperature inside is consistently above freezing before bringing in pots of plants overwintered outdoors under thermal blankets. This year I'd like to start a bit earlier. I do have a couple of small heaters I can run with an extension cord from my house but they're definitely not up to heating the whole space. I'm not inclined to buy larger heaters at this point.

As everyone who has one, or has read enough postings on this forum, knows Rion's are notoriously "leaky ships"
(not necessarily a bad thing in the summer heat). My 1st step will be to plug as many of those leaks as possible with weatherstripping and bubble wrap over the roof and side vents.

Here's where I'm looking for feedback: I thought I'd try lessening the amount of space to heat by building a cold frame within my cold frame, so to speak. I have 36" high benches running the length of both sides. Basically, I thought I'd run a clothesline the length of each bench and drape bubble wrap over the benches with a heater and small circulating fan under each bench.

Obviously anything is better than nothing, but I wonder if I'm being too simplistic? Anything I should be thinking about that I haven't mentioned?

Many thanks, Iain

In years past I've set up a structure within a greenhouse using a canopy frame with shorter legs. Then I also covered plants under that with floating row cover. I did suspend fans at both ends within the canopy framework to help move air around. I monitored temperatures at three levels with thermometers that would save the high and low temperature readings. The main problem I encountered was that there were "cold spots" where temperatures dropped below freezing and I lost 10% of my plants (tomato). To me that was unacceptable for that crop and I've been heating all my structures with wood stoves for the last 5 years- a much simpler and more reliable approach. I still run circulation fans; I close cracks as much as possible ( a can of "Great Stuff" goes a long way but it looks like crap); I use at least 2 inflated film layers over all my structures, one benchtop even has bubblewrap sandwiched between 2 plastic layers. Yet there is always a point where I wish I could gain a few more degrees inside these structures.

The expert on this subject IMO is Dr. Adam Montri, Michigan State University. He has done more research on this concept than anyone I know. His setups may not fit your system but the ideas are somewhat the same.

At night everybody who owns a greenhouse would like a few degrees of warmth. With my 30x96 greenhouse I need to fire my woodstove as hot as I can to get a 20F change (from outside temp) most nights. That's a main reason that I won't be moving plants into it for another few weeks.