Serj thanks you for the update. I would like to ask you one question - why don't you paint the interior of your greenhouse white, doing so would reflect so much more beneficial light to you plants? - Millet

brian, when I purchased the double wall polycarbonate for my greenhouse, it did not come with any instructions, other than which side of the sheet to face towards the sun. I used the 2-inch wide metallic silver sided tape and sealed off both ends of the sheets. This was 3 or 4 years ago, and at least up to the present time none of the polycarbonate sheets have ever developed a buildup of trapped moisture. They look the same today as they did the day I instinctual them. I guess, as always, time will tell. I'll certainly let the forum know if it ever happens. - Millet

Great job,Serj...I will build something like your greenhouse in the future.I was thinking a lot,but now I'm sure to do.It is ok in your zone 6,I hope that it will be ok in my zone 7...

citriko, i think in your zone 7 it should work much better.

Millet, good to hear that this can work fully sealed. I might do a test and seal half the edge, leaving the other half breathing, and check the temperatures to see if there is a difference. Now that I have insulated the walls and floor of my raised greenhouse the largest heat loss by far is the poly glazing.

Serj, your setup looks awesome. I am in the same zone 6 and I have to run a heater at night. Did you dig that out by yourself, with a shovel???

Yes, Brian, i digged it by myself with shovel. It was very difficult. I think your USDA zone 6 is not the same as my zone 6. My latitude is 50 degrees, your latitude is 40 degrees or so, isn't it? It mean that you have more sunlight, your fall is more late and more warm and your spring are more early and more warm.

I can't even imagine how hard that was to dig out. I dug an approximately 1 cubic meter hole for a small pond and even that was unpleasant. I hit very firm clay soil about half a meter down.

Yes, I am at 40deg latitude and so likely more sun. My area has average first frost in early November, and last frost in late April.

If I had more land I would try your design. In fact, the more I think about it the more it resembles the design of a small swimming pool. I wonder if you could empty all the water out of an in-ground pool (rather than winterize it), cover it with a polycarbonate roof just like yours, and use it as a greenhouse until spring. Then fill it back up with water in the summer.

The walls of the pool could be damaged because of the lack of water volume serving as a heat sink and elastic amortizator.