With the use of row cover, you don't need a pond or other jugs of water. I grow and harvest year around here in North central Kansas. Even on cloudy days, you still get some solar gain. It just won't be as much as a sunny day.

The larger your structure, the warmer it will be in the winter. It will heat up slower and cool off slower.

Jay

Dirtslinger, remember that the point isn't to grow vegies year round. The point is to harvest them year round. Yes, temperatures drop a lot in the darker, colder part of the year, but lots of things will hold just fine under the right protection, and will be better than if harvested and root cellared.

Next to your name it says you're in zone 6. I'm in zone 5, coastal Maine. We get heavy snows that will take down a round arch high tunnel. I use a wooden homemade gothic arch design that sheds snow easily. There are metal frames typically called "New England Style" that have enough of a pitch to shed some snow, but I've learned that I don't like metal frames. I can repair a bent or broken wood frame. Rot isn't a problem above foundation level.

Coleman's idea is to have row covers within your high tunnel. There's no wind in there, so they don't get blown around. You can put on several layers if you want. Coleman uses arches bent from light metal electrical conduit. I use 30x54" box frames and lay old storm windows over them. Sometimes I lay plastic over that. You can give it a lot of protection this way. If you had double plastic on the skin, you'd get convection loops between the warm soil and the high tunnel skin. With row covers, the warm air is held at plant level.

Another thing Coleman has been doing lately is overwintering onions under his conduit arches. He covers the arches with spun bonded row cover, then a layer of greenhouse plastic, and weights the edges down with sand bags. I think he opens up an end occasionally to trap voles, but mostly it stays closed all winter. The onions winter over and get an early start.

Here is a link that might be useful: Gardening The Hard Way

One other thing: Black barrels and jugs don't heat the greenhouse. They don't add any heat that isn't already there. They just moderate the temperature some. They take up room too. I think it's better to have a bigger greenhouse with the peak running east-west, and the north wall somehow insulated. I've tried to put multiple layers of lumber wrap (free cheap tarp) on my north side.

Okay, make that two other things: I know one guy who has a fan system. It takes in hot air from the peak of his greenhouse and blows it into perf-pipe buried under his growing beds to get more heat into the soil.

Hi there. I am in z 6a according to the new USDA zone maps... in western Mass.

First, i want to ensure you that you certainly can GROW crops 4 seasons. I just harvested beets that i sowed in november. I have been eating lettuce and spinnach all winter and just picked raddishes that i sowed in late january. So don't think you are limited to using the GH as a big cold storage cellar.

I looked at a few designs before starting mine.

I looked at the sunny john design which has plennums running beneath the surface to heat up the soil. I rejected that as too expensive and too much work. There are studies that show moderate success with that.

I looked at excavating the soil and replacing with stone and circulating the air through the stones. Again, while it has some benefits, i would need power and the stone would be expensive.

I went with the solaroof design which is a double greenhouse that uses soap bubbles as an insulator at night. I never got that far as i still haven't run power out to the GH. So i just have a double walled gh, with 2 foot minimum airspace.

My specs:
GH interior 48 x 22
GH exterior 52' x 26'
GH height interior 11'
GH height exterior 14'

Both were built with commercial grade greenhouse tubing. If i were to do it again i would save $$ by framing the interior with something cheaper.

Heating: None
Ventillation: 8 foot wide x 2 foot high gable ends vent. The vents are at the peak of the gh to allow heat to more easily exit. I also have an 8 foot wide door on one end. I will likely add a door on the other end to aid in cross ventillation.

I never added the bubbles. I would like to so i could determine if i get additional zona protection.

Some of the more interesting "successes". I grow tomatoes into december. I grow all sorts of cool weather crops: peas, beets spinnach, lettuce, raddishes, chard, green onions, dill, thyme, rosmary throughout the winter. Some i actually re-sow midwinter.

I "overwintered" citrus, which died back but sent out new shoots. potatoes keep trying to grow but die back with each "Freeze". They are now growing in ernest.

I put "freeze" in quotes as i am not sure of the interior temps. Outside temps reached -14F last year and i still did not have ice in the GH. I used to get ice, but i built a water tank that holds 1500 gallons and have not had frost or ice in the GH since. I have fish in the tank.

I have not read the winter garden book you have. I have done none of the calculations regarding thermal masses. I can't tell you whether row covers are better than a second GH layer, but if the book says you can't GROW crops but can only overwinter them, then based on my experience, row covers don't do the job as well.

I do not have below the ground insulation.
I grow my crops directly in the soil.

Ask away...

Some excellent points here, thank you.

The bigger the better makes a lot of sense. Great link as well Huisjen- does your soil dry out early enough for planting or must you wait to get starts in?

And Poppa- are you saying you have basically an inner and outer greenhouse? Are they attached structurally? Did you build/bend metal yourself or is there a source to purchase these? A min/max in there I'd think would be priceless.
Also your 1500 gallon tank- what did you use? Is it sunk in? Do you heat the water at all and has the water frozen? What sort of fish- a food source or something to keep the algae down?

yes, an inner and outer gh. The dead air space is not used.

They are attached at the doorway. Not for any real structural integrity but i have a a removable panel at the doorway so i can walk inbetween the gh layers should i need to. The base of the dead air space is graded and sealed with plastic to allow for the dying bubbles to return to a tank (which is not installed yet). The tank is the soap solution reservoir. Additionally, there is a very basic scaffolding above the doors to site the bubble generators. WIll be one at each end.

I thin if you look at the farmtek catalog you will find the type of frame i used. It's something like 1 7/8" dia. pipe. It's been a while since i verified that so i'd have to double check to be sure. I subscribe to several auctioneer websites and get notices for farm sales. I bought 254 feet of GH for $200, so price is a non-issue there.

Yeah, one of these days i'll get the min/max sensors. I want to hook them up to my computer so i have never bothered since i have no power out there. it's about 500 feet from the house.

The 1500 gallon tank was a design i saw used in Africa. Very cheap to build - around $50! It's just standard fence wire (not chain link, just something you'd put around a garden. The wires are maybe a 3" and 5" spacing?) This is not chicken wire though. It is thick enough to self stand.

I used about 25' of fence to give me a 8 foot diameter tank. I set it in the ground as the fence is 4 foot high and i wanted the tank under a bench so it takes no room in the GH. So the fence was set maybe 18 inches down. Once the fence was up, i used standarn fanfold foamboard insulation, like they use under house siding to line inside the wire. The i used leftover poly from the greenhouse to line the tank.

I do not heat the water. I get no ice at all. Last year outside temps dropped to -14F and this year's low was 2F.

I originally wanted to grow tropical crayfish from australia called redclaw. They get up to the size of a small lobster, about a pond and a half. Unfortunately, they graze algae and ate through the plastic lining. Now i a just playing and overwinter my goldfish and i stuck a couple of yellow perch in there. I would like to raise fish for food but hve not settled on a species yet. Either Yellow perch or some type of catfish.

I also have plans to use the tank as part of an aquaponics setup. again, i hve no power so raising fish intensively or as part of a system will wait until i decide to bring power out or i add some solar componant. Mostly i use the tank as my water source for the winter. I fill it in the fall and take from it as i need.

I have a few Cold Frames that I employ. I am zone 5B/6A zone. I recently came up with an idea of constructing a solar water heater above my cold frame and piping the heated water through rocks underneath my Cold Frame. So instead of sitting on the ground, my Cold Frame would be elevated about a foot. I do container gardening in my Cold Frames, so direct planting is not required.

I plan to use a closed-loop systems that distributes heat via convection. The solar water heater would be black hose in a box with wooden/insulated bottom and sides and PolyCarb on the top. I am hoping that with about one ton of thermal mass underneath I could keep some peppers/tomatoes going until early December, then switch to cold veggies for Jan/Feb and start bringing out summer plants again in March. I start all of my plants in my heated grow room, so I can time them for any time I need.

The closed loop system would simply be a black garden hose filled with non-toxic anti-freeze and water. That should keep things good down to -20, and I cannot remember a time when it got that cold here. The actual costs are minimal and the construction is so simple even a non-handy guy like me can do it.

GarlicFiend,

Sounds like a good idea. I was wondering wouldn't the solar collector reduce the light level for the plants or do you plan to install the collector elsewhere.

If you do get to construct the collector, please do post some results. I would like to do something like that.

Dirtslinger, I never have a problem with the soil being too wet. Even if it floods around the greenhouse, the soil inside is a couple inches higher than the highest possible water mark. If anything, the opposite is the problem. Things can dry out in the cold frames around now when the sun moves moisture around.