I live in Northeast Florida, and I use 6 mil. There is only one layer, and I use two heat lights (not infrared) and a quartz heater. We also use that 3/4" 4x8 sheet of foam insualtion all around. It is 8'x10' by 7' high, and it is enough to keep the frost off, but does not get nice and toasty in there. Last year we had a double layer, and it worked much better.

But you need to get some input form other northerners, I don't see how you can use it unheated, as cold as you get. We just went through the cold wave here, and it only got below 30 a few times. And I was sweating that little hoophouse! Your endpieces sound very good, and can help hold heat in. But I don't know about the unheated part.....

Cheri

We use one layer of 6mil in SW Ohio and start tomatoes, cukes, zukes and canteloupes usually in mid to late March.

We do use mid weight to heavy weight row covers over the tender crops when it gets below 32ËF, We also use buckets of water as heat sinks. Bucket heats up during the day and releases heat all night. They make a difference.

Lucy

I use a heated greenhouse and when things get too tight - move flats to a 8 x 20 hoophouse made with 6 mil plastic. There's no heat but the hoophouse is only about 4 1/2 feet tall. To allow me to stand upright, I've removed 18 inces of earth from a 2 foot wide center path. That makes for nice, deep growing beds on either side, I can stand upright, and it seems to help control the temperature. Deep ground temperature here is 55 degrees year-round.

Not much is in the hoophouse until about April 1st and then only things that are frost hardy. I've got enough room in the heated greenhouse for the tomato plants, etc. Still, I doubt if we would have any trouble with tomatoes in the hoophouse if we made use of it for them even tho last frost is usually about April 21st.

I've seen research which showed that 2 layers of glass or plastic provides very little benefit if they are closer than 1/4 inch or farther apart than 4 inches. I believe that ohiorganic has good results with row covers even tho' they are far below the hoophouse cover since they are so close to the warmer soil.

Digit

Digit,

How do you keep water from standing in your hoophouse during a heavy rain? The idea sounds interesting and I might like to try it!

Maybe it's obvious to most, but to get the insulation value from double layer plastic you need an inflator fan on at all times to keep a layer of air between the plastic sheets.

We just put up our first hoophouse this fall (20x32), for exactly the same uses as Heirloom_Lady, starting this spring. It came as a kit, with 6mil plastic, and included the fan. I hadn't quite registered on the fan part till actually ordering and building it. We had to run 200' of heavy duty extension out into the field to power the fan, but I'll replace that with a little solar panel and battery this summer. The fan also makes the hoophouse more aerodynamic or whatever, more wind-worthy, but if the fan stops, there might be a problem with the looser layers vibrating in a high wind (I've read that emergency power for the fans is a good idea, hence the solar panel thing, around $250 for all the gear, and get rid of another wire!).

We're planning to set out hardy seedlings in March/April, and than have a few early tomatoes and peppers as a tet during the season. Want to build another, bigger unheated production house for next winter, and use floating row covers inside for winter spinach, mache, carrots, etc (a la Eliot Coleman).

tbronson: I would be intrested in knowing were you got your kit from as $250 would be in my budget. Any good website you could direct me to would also be helpful. Thanks Patty

Patsyptrsn: Sorry if I was unclear. The $250 refers to the stuff (battery, inverter, panel) for powering the fan, instead of plugging it in to the grid! The hoophouse itself was pretty expensive, around $2,000+ for the whole deal (steel frame, rollup sides, 6mil greenhouse film, FAN, hardware, and wood for framing bought separately). (We don't have money to burn, I hope to build cheaper, bigger production houses from scratch, but this first one I wanted something 100% winter-proof and solid for early seedlings, and it's a good deal for a kit.)

Try FarmTek as a source for - relatively - inexpensive hoophouses. www.farmtek.com

I'm not sure a solar panel and battery set up are going to be of much use to you in the winter.

We've had six high tunnels in use for years but last year we need to heat one during our long cold spring. Our son suggested we use a propane tank heater. This small attachment that screwed on top of the tank kept the HT nice and warm during the night and the sunshine did the rest of the job. I know he didn't go out of his way to find it. He was using it to heat a shed.

For earlier planting some type of reliable heat bachup is a necessity. I found out last night after sticking in 200 tomato plants that my main heat source, a coal stoker stove needs a little repair work. The one backup portable propane heater must be faulty too becuse the tunnel was full of smoke afer an hour so I shut it down and ran the exhaust fan for a half hour. Fortunately the outside temp. only fell to 48F.

The next few nights will test any heat system if you have plants in a Northeast greenhouse. I'd advise anyone to make sure the systems are operable BEFORE planting. I think I'll have my corrections in place by tonight. There is no better incentive like a greenhouse full of plants to get excited about on cold night.

Sorry Sherry, Got sidetracked and missed the main question on my previous post. Yes, a double layer of plactic, inflated, will considerably lower heat loss at night. A few greenhouse supply companies provide tables to show supplemental heat needs (BTU) in single vs. double layer plastic. If you are insistant on a no-heat system you could even use a low tunnel within the inflated high tunnel.

You need to use caution with sunny days like today in PA that you have a means to ventilate excess heat. My greenhouse is closed but the intake louver and exhaust fan is running constantly since 10AM today just to keep inside temps below 90F. An adjacent tunnel, unplanted and closed is reading 120F. That temperature will be too hot for plants.

I don't want to downplay your endwall insulation. It may be a factor in a 20' long structure. If I were you though, I would look into the Magni Clear pool cover that has been discussed in this forum in the past. The bubble wrap cover provides an insulation for the entire structure. If you sandwich it between layers of plastic you may not need to inflate it.

ohiorganic, do the buckets of water really work? I had heard of that before but have never actually communicated with someone who used the method! We have a couple of small movable hoophouses we use to get the plants out of dormacy and ready for opening on Mother's Day weekend, we also use it for seedlings, etc. No heat, but the bucket idea sounds interesting! Thanks for the info.

yes the buckets really work but they are not a replacement for supplimental heat like propane. But they do keep the temp above freezing in the house as long as it is staying above 15ËF outside

Here is a link that might be useful: How to Build a cheap and Portable Hoophouse