I feel your pain. Retractable insulation is a great idea, but difficult to make work. Even with the chlorine issue aside, anything rubbing against your poly in the wind will make it cloudy, even other poly. I have an inflated double layer, but from the hip boards down, it doesn't inflate, so that the sides can roll up. After one year of rubbing together, those layers of plastic look like milk. The inflated part is still perfectly clear. A pool cover could do the same thing to your poly. I would want a separate frame to hold it, which is not exactly easy. You might try something like a fiberglass blanket that is soft on the underside where it touches your poly. Plastic-on-plastic seems to destroy itself.

Thanks Cole. This situation seems to be one of the most difficult. I have spent so much time just trying to think up things I could do and everything has a major flaw. The only thing that even seems feasible at this point is to shell out 1500 bucks for a double wall polycarbonate paneling to cover the entire greenhouse.

Between the cost of heating and the cost of a new roll of plastic every 3 years the cost might just end up being worth it. Then I could toss a magni clear over the polycarbonate and screw it right into the wood frame.

1 layer of plastic costs 800 dollars in heating over a 2 month period. An educated guess would be that a double wall polycarbonate and magni clear could cut that by more than half. But I am not sure if the pool cover will damage the polycarbonate too?

Chlorine degrades the UV inhibitors; you'd have the same issue with the panels.

You could do an inflated double layer with 6-mil on the inside and a single-year poly on the outside. Then whatever damage the pool cover did to the plastic wouldn't matter, because you'd be throwing it away at the end of the season.

That's a good idea Cole. What sucks is I have 3 levels of shelves in the inside and it will be a massive pain the arse to pull them out do that.

The only thing I wonder about is light levels. I am in the process of paining all the wood white now because the light levels were about 15% lower than what I wanted last year. Even though it would be a bit of extra work I do like the idea though. I just wonder how much sunlight will be lost from 3 different layers.

Soulreaver, who told you the solar pool cover would degrade the plastic film? I've had a layer of MagniClear sandwiched between 2- 6 mil film layers since July, 2007. It looks in great shape and I expect it to last quite a few more years. There is a slight milkiness to the appearance but plenty light gets to plants to the point where I pull a shade cloth over the structure for much of the spring.

One thing you want to avoid is bare PVC pipe touching the film. I have pictures from years past to show damage which looks like the PVC pipe was heated and just melted through the film whereever it touched. That occored for me when I installed 2 layers of film over anothger structure and the inflation fan balooned the inside layer against the PVC pipe which was to protect my electric wires.

Bmoser I appreciate the feeback but I have 1 layer of 6 mil film and last year I did not like the light levels in my wood framed greenhouse. Some tomato flats had short plants in the middle and larger plants at the end. My greenhouse has an east/west angle to capture the most sun from late winter early spring when I need it the most. I just finished painting all the wood white but I don't understand how the light levels are not where I want them to be when others seem to have 2 or 3 layers on their greenhouses and get plenty of light.

Don't get me wrong the light levels are not horrible. I would say they are 15% less overall than what I want. I am hoping white ground cover over my brick floor and white wood over non painted wood is going to make the difference. If I switch to polycarbonate panels though I definitely don't want to be risking using a pool cover and damage them since they are so expensive.

I don't quite understand your setup. Do you have polycarbonate panels (exterior) and a layer of 6 mil film(interior)?

IMO the panels will block more light than either bubblewrap or multi film layers. I've only used it on ends but for a product that is meant to last many years the light transmittence goes from fair to poor rather quickly.