Bubble-wrap "sandwich"?

Adding the second layer of plastic to my GH has been a two-year project. Sigh.

At any rate, I've researched the subject of keeping air between the layers, and the cost of the little fans, mounting kits, jump hoses (to push air into the sidewalls), etc.

All of which gets a little pricey, not to mention the cost to operate the fan 24/7 for 4-5 months.

So then I started thinking about bubble wrap. Any reason why I can't use it to maintain this all-important dead air space between the layers? I know it'll eventually break down, but now that I have my handy little "snap" clamps to hold my plastic on the PVC frame, it won't be too hard to put the bubble wrap and second layer on in the fall, then take it off and replace it with shade cloth once the risk of frost is past.

I think Jody used/uses bubble-wrap to insulate her GH, but I've never heard of anyone using it as the middle of a two-layer plastic sandwich. Any reason it shouldn't work, or I shouldn't do it?

(I found a local source of bubble wrap, and estimate it'll cost about $30 or $40 for it, with tax - still less than the fan and hoses.)

as for the fan and hoses,I bought a small appliance fan for 10 bucks at HD and set it up inside a peice of duct work,and then attached it to a dryer hose,in all it cost me less than 25 bucks

I cut an X in the inner layer of plastic and stuck the hose in it .I used tape to secure it.Its been there for a year now,and even though the fan is not rated to run 24/7 it does a great job.The only problem I had was that it came loose from the duct wall and was rattling,DH tightened the screws down and haven't had a problem since...

I'm thinking of adding the bubble wrap to mine just for some added insulation.It gets to -25 and lower so I need all the insulation I can get.....

Terry, here's an earlier thread on the subject of bubble wrapping a greenhouse, though not the 'sandwich' idea:
http://davesgarden.com/t/48236/

I'm curious here??? Does the bubble wrap act as an insulation barrier????O The reason is, as the sides my greenhouse are glass...would that work also, the bubble wrap?? Elaine

cc, thanks for the tip on an alternate fan - that sure beats the $75-$100 I was looking at to get a GH fan. Weezin, thanks for the earlier thread. I think I'll check and see if the local supplier can get UV-rated bubblewrap. Even if they can't, $30-$40 for a season's worth of wrap could be pretty cost-effective if it cuts down on my heating bills as I'm hoping the second layer will.

Roselaine, my understanding is that the dead air space in the bubbles acts as an insulator. I've heard of people wetting their glass or polycarb, and putting the bubble wrap's smooth side on, and having it stay in place fairly good for the season.

I'm rather interested in the bubblewrap idea, as well. Our small greenhouse has fiberglass siding, and after the first chilly spring, we added a layer of visquene to the inside for a vapor barrier. I begin putting seedlings into the greenhouse in early April, and we can still have some pretty cold, windy weather that time of year. The extra layer really seemed to help hold the heat in. This may be a stupid question, but would the bubble wrap refract the light differently? You can tell I have no idea how sunlight works!

I was thinking about using it on the north side,don't know if it would be worth the trouble.......

My house has very old, single-pane metal crank-out windows that don't close very well.

Every winter, I place a layer of bubble-wrap on most of them and it works fairly well to insulate. I cut out a few holes in some of them so I can see out, like over the kitchen sink, and the large front window. The first year here, I used just a layer of poly but the bubble-wrap seems to insulate better.

The windows that face west get the most sun in winter and are filled with my house plants which seem to thrive in the filtered light through the bubble-wrap. I see no reason bubble-wrap wouldn't work for a greenhouse!