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shelley1962 Churubusco, IN(Zone 5b) Jan 16, 2005

Because we installed our plastic during the cold months we couldn't get it pulled very tight. The instructions say there should be about 12 inches of air space between the layers...ours is more than that in some places. What is the down side to having more air space between the plastic?

Thanks in advance.

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CricketsGarden Nauvoo, AL(Zone 7a) Jan 17, 2005

I dont think their is a down side to more air between the plastic. The air space acts like insulation. So i would think that its just more insulation . lol. i could be wrong. just an opinion.

cricket

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kathy_ann Judsonia, AR(Zone 7b) Jan 18, 2005

I would think cricket was right too, we had one layer of plastic up in our greenhouse, after the greenhouse l6 x 32 heated with wood stove, got down to 30 one night, temps outside were in the teens, l2 degrees I think, we decided to put plastic up inside as well, there's 6 in between plastices on the side and 4 in inbetween on the ends. our temps in the greenhouse now with l5 degrees outside was 60 at night, no matter what we tried before, we couldn't raise the heat in the GH, NOW we're cookin LOL

kathy

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btailoring Stockport, OH(Zone 6b) Jan 18, 2005

Thanks for the info Kathy ann- been thinking about doing that very thing in my 12X12 greenhouse-also lowering the ceiling with plastic (has a pitched roof)- guess that's on the project list for tommorrow! :)

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Michaelp Erwin, TN(Zone 7a) Jan 20, 2005

The down side to too much space between the plastic layers is--the larger spaces allow the air between to have its own convection currents transfering heat from inside to out, -- in cold weather this raises your heat costs.

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shelley1962 Churubusco, IN(Zone 5b) Jan 20, 2005

Thank Michael. Knew there must be a down side or I would be seeing balloon greenhouses all over the place LOL. Is there a calculation that would tell me at what point the convection currents change? I'm assuming someone already did the calculations and that's where the recommendations came from but I'm one of those "odd" ones that likes to know where the numbers come from. Thanks

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DeepRoots Willacoochee, GA(Zone 8b) Jan 20, 2005

3-4inches is ideal.

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Michaelp Erwin, TN(Zone 7a) Jan 20, 2005

Deep Roots is right--at 2 inches there is no air movement- after 4 inches it gets to be enough to begin to cause the higher heat costs I was refering to.

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shelley1962 Churubusco, IN(Zone 5b) Jan 21, 2005

thanks for your advise. As soon as the weather warms up we are going to pull it tight.

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