Colem:

Our greenhouse is larger and fairly different than yours, and we're also in zone 4-5 so take this as you will...but yes we had an odd moment as you describe when we first built out GH 2 years ago. For me personally I had a lot to learn. I assumed the GH was somehow magic and once I built it plants would be happy 12-months out of the year. Sadly this was not the case and I managed to fry and freeze a few test plants. A few years later and lots of reading and purchasing and we've finally found a 12-month happy zone and we love the GH. Ours is permanent and much larger than yours so some of this may not apply....but here goes:

Cooling. Yes a clear sealed room gets hot on a sunny day. Venting and air movement is a must. We have 4 different roof and front wall vents that open and close automatically and the roof vents even have exhaust fans to help move hot air out. We also have a circulation fan that is thermostatically driven to keep air movement going in the GH. We also added 35% aluminet shade cloth to cut down on sunburn and telp with the temps a little. Finally we have a timed misting system we built outselves. This cools the air and increases humidity which the plants love.

Heating: Yes it gets cold outside and the GH is perfectly happy at night being the same temp as it is outside the GH. In season one I desperately tried to heat the GH with a simple radiator style 5K BTU electric heater. Long about Dec it became clear that I'd need more so I added a 30K BTU direct vent propane heater. This did a great job, BUT there were a lot of peaks and valleys in the heating pattern, not to mention a hefty $$ associated with propane. In year 2 we covered the whole GH in a clear solar pool cover. This worked fantastic, saved a lot of money and evened out the swing in temps.

As far as bugs, we have screens in all of our openings so we see very few...but I'd be guessing they like the heat or something else in there.

I'm not sure how much $$ you want to invest in a 6x6, but after a few years of reading, learning and modifying, we've now found a really happy place in our GH and we use it 12-months out of the year. It was cool to have fresh tomatoes and potatoes in Feb and even more fun to be enjoying strawberries, beets and cukes already this season. I experienced the frustration phase you're currently in and did a lot of second guessing on a much larger scale...but now we start seedlings and do all sorts of growing and the GH operates itself. Whether I'm home or away the GH takes care of itself....so hang in there. Owning a GH is a process and there is much to learn and more importantly a lot of experimentation that needs to be done.

Fuzzymoto - do you use HIF lamps for lighting in February?

No. We use NO supplemental lighting. We have great southern exposure, and yes some of the plants can get a little leggy, but still acceptable.

If it's 80 outside, you don't need a greenhouse. think of it as a way to extend the seesons. start things earlier, and try a fall crop started in late summer.

I am also having a problem with the heat and air flow isnt enough. A misting system is a great way to solve this problem. I ran a test the other day with a common garden house and a misting nossel. With only one, it dropped the temp from 99 degreed to about 85. It did get things a little wet, but hopefully when I get the money to invest in a low-pressure misting system, it will be a finer mist. (Only around 30-60$ for a basic one, but Im a little broke.. haha)

Not to go off topic, but if anyone knows, will a misting system cause the some plants to be more substitutable to blight? I plan on getting a timer to mist for 1 min, every 10-20 mins.

I don't know about blight on plants, but I had a lot of trouble with mildew on plants (and pots and shelves) last year (year 1 for me and my GH) when I kept everything too moist in there. I used a misting nozzle on the hose and misted whenever I got home from work. From that experience I learned that one giant blast of mist once a day isn't a good thing. This year I'm trying to come up with a system to mist briefly throughout the day for a steady level of moisture. Although I have a swamp cooler in there and adequate venting, it's still not quite enough.

Like you Colum, I also had that 'OMG' moment when I wondered why I had wanted this. I didn't dare mention it to my DH because I spent a boatload of money on it and I didn't want him to know how crazy I am. There is a learning curve associated with it and I am still trying to learn all I can about managing and growing things in it. I also thought it would magically sprout and grow everything I planted - not so. I killed a few plants last winter when I didn't set the thermostat correctly and I had frost on the inside.

All those times I went to these giant nurseries and they had thousands of uniformly perfect plants in rows on tables, it just seemed like it must be so simple. I figured, "Hey, I'm smart, I can do that." But, so far I haven't. Without constant attention, automatic watering systems, temperature controls, just the right amount of heat, just the right amount of light and just the right seed starting mixture, it just isn't magical at all.

I have to say that although I haven't had great success with seed starting, I haven't lost a cutting yet. Without fail, every cutting I have set in soil in the GH has sprouted roots and grown into a healthy plant. That's a small success, and I'm happy about it. Some of my seeds have done OK.

Cheryl

As I said we're in Zone 4-5 and we use our GH 12-months out of the year. This includes January lows in the -19F range and July highs in the 90F range. With vents, fans, Aluminet shade cloth and misting for summer and two heaters and fans for winter we've found a very happy place.

I think something people may be overlooking here is how useful a GH can be to grow plants WITHOUT competing with bugs, and other rodents. We planted raspberries and sunflowers outside and some critter went through them like a bear through a salmon. At least in the GH I don't have to deal with that.

Our GH is all glass so even with shade cloth it can get a lot of scorching sun and heat. When it's really hot or when we travel we activate our misting system to even out the temps. It CAN certainly get too wet in there, but with solid concrete floors and floor drains ours dries out just fine. If we get three or four days of overcast rainy weather with the misting system on it gets wet, but even then not so bad.

We built our misting system outselves out of drip irrigation parts and a hose timer. Nelson makes a hose times that actually has a misting cycle on it. It does cool the GH considerably, but I find now with our combination of shade, vents and fans, that we need the misting less and less....but your mileage may vary.

It takes some time to learn, but the better we get setup in the GH, the more magical it can be for the plants.

This is a first for me so please feel free to point out any mistakes or misconceptions. That shade net stuff seems a bit expensive, $3+ per ft. They have an foil type isolation for the attic closer to 35 cents a ft. Use a spray glue and set it to a fabric for reinforcement and glue it (fabric side) to a piece of PVC. Put a piece of doweling, cut a little longer than the PVC through it drill a small hole in doth ends of the doweling, just big enough to take the string that is used to lay out a house foundation,that is the draw line for the screen.
For the tract drill a hole through two 2x4 just big enough for 1/2 pvc to go through. set them together so you can set a jigsaw on top. Put the hole near the top and edge. Then cut off enough of the edge of the 2x to leave your track opening use this as your stencil. Put it in a vice set the saw on top and slide the pvc through to cut open the tract. Use screws to set it to the beams and a hair dryer to bend the pvc it so you have a nice smooth curve. They make steel tracks but I am not sure how you can bend them to a curve. Put the dowels in the tract so the foil faces outward. Draw up the screen when you want the sun and let it out when you need the shade. I have never made one but it is just a thought.

msnewfarmer-
I don't know where you are getting those prices on shade cloth; about 40 cents a square foot is typical. When you talk about $3 per foot, that may be for a lineal foot that is 10'-12' wide. I did a little Googling and here are some representative prices...

Here is a link that might be useful: Shade Cloth

I forget what we paid for Aluminet but I don't think it was that much and Aluminet is one of the more expensive shade cloths. There are cheaper. Your plan sounds like it may work although I don't know what the material you mention is. We installed ours inside so it's stretched pretty tight, and if you install outside it takes a beating so you'd want to ensure it's buit and attached well.

I relate to this post exactly! I have a 6 x 8 GH kit arriving tomorrow and I am already thinking of returning it. I was obsessed and had to have it and now I don't know why. I am in Houston where is so hot in the summer. I don't know if I am up for the challenge of heating, cooling, venting etc. I thought it was magic too, and I have no idea how to use this thing.

Sorry I just realized I don't have any useful advice but now you know you're not the only one feeling this way.

Save electricity.

Not enough vents.

No insulation, heater or thermomass.

The good stuff. Once you figure out how to utilize the gh you will wonder way you did with out it for so long. Its easy but time consuming to vent manually but to me its worth the time.

Picking tomatoes when others are just starting to plant theres outside is a huge plus. That is the end of May here. Here in Zone 5 I suffer a seroiuos case of zone envy. However my hoop house, unheated, is allowing me to keep up with and out perform others from across the nation. Not bad for around $250.00 and some capentry skills.

Colem, A 6x6 is very tiny but you can still start plenty of seedlings in there a month or more ahead of your normal outside planting times. With a heater you can cheat mother nature big time. You don't mention your zone so its a mystery. I wanted my hoophouse large enough to grow crops right in the ground and at only 12' x 16' x 8' I'm able to do that.

What I have done with my hoop house to give you an idea...planted maters a full six weeks earilier, planted cukes, melons, zuke, yellow crookneck and peppers one month early. Started all my cool season crops way early and put sizeable transplants in. Managed to sell tomatoes plants that almost paid for my plastic, or paid for all my heirloom seeds and some. So everything I'm growing this year is free! Thats over 50 varities of veggies. Of course 17 of them was tomatoes. Now for the fall and winter months I'll be growing cool season stuff. I never had fresh salads for thanksgiving or x-mas but this year I will! Hope that helps convince you!