i would think about what types of minimum temps you want to maintain and how you would heat it. That might help you decide how big a tunnel you can afford to maintain.

We wouldn't use supplemental heat. I may have misled with the comment about early summer squash. I'd like to give some vegetables an earlier start but during our NH winters I don't expect to grow anything except cold hardy vegetables.

Unfortunately, my husband would prefer that I not grow things like kale and rutabagas. But, we both agreed that I need to grow more carrots. We also grow parsnips but don't harvest until the ground thaws in spring. I'd like to have some of our root vegetables available during the winter in a high tunnel and some wintered over in the garden. We also love the idea of having fresh green beans into November.

I have/had 8 high tunnels over the years. It is best to go as wide as possible. Currently I have 16, 18.5 and 30 feet wide. The reason is frost/ cold ground will creep in along the edges, unless you go to extreme measures and install insulation around the base, buried in the ground.

So if you have a 12 foot building and the frost creeps in 1 foot on each side, you only have 10 feet of growing space. If you have 16, you have 14 feet and 30, you have 28, you get the idea.

Also, a wider building will be taller. It will warm up slower and stay warmer longer. I noticed a huge difference this year when I put up a 30 by 48. The wider, taller building has a larger volume of air inside.

Finally, it is easy to go longer instead of wider. Just remove the endwall and add more bows. To go wider, you would have to get a new building. SO go wider instead of longer.

This was my 12 by 18, it is gone now. Way to small.

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Here is my 16 foot wide, it is also movable.
http://i587.photobucket.com/albums/ss315/jrslick/IMG_1599.jpg

Here is one of my 3, 18.5 wide ones.

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Here is my 30 foot wide one.
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Yes it does have another tunnel inside. I built it over a smaller tunnel and then removed the tunnel inside.

jrslick, thanks for posting the photos. The 12' wide one does look too small and knowing that I'm probably going to have 1' on either side too cold makes a big difference in my "calculations".

Since we don't have any snow cover right now I was able to pick some spinach this week. I was amazed at how sweet it was. Different taste that during warm weather. This spinach is growing in the open ground without any protection. It's exciting to think what I can grow with a high tunnel or hoop house.

JRSlick has some nice houses, but I still believe that for New England, you need a higher, sharper peak. I like my house that's made with wood strapping trusses. I built a 16x24 house several years ago, and paid only $100 for the strapping and screws. I used a lot of scavenged lumber and some used but functional greenhouse plastic to cover it. The gothic arch shape is very strong and has shrugged off a 16" heavy wet snowfall with no outside intervention. Last year the operation down the road from me lost several 20' wide circular arch steel pipe tunnels to snow.

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In this case, bigger is easier to build than smaller. This house uses 14' strapping bent to a 134" interior radius. The tighter you bend, the more likely you are to break things in the building process.

Like folks have said, once you have the basic design, it's easy to extend the length.

Here it is with spinach a year or so ago.

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A little extra space just for lounging around in on a cold but sunny day when it's 80ð in there isn't such a bad thing.

Dan

Thanks, Dan. That structure is beautiful! We get those kind of snows. Weird this year not to have any snow cover after a snowy Halloween and Thanksgiving.

I would certainly err on the side of going bigger than you might anticipate needing rather than "just right." The larger structure is going to moderate temperatures better than a smaller structure, and any time that you get near the edges the ground is going to be a little more susceptible to frost plus more of a pain to work around. I just came in from trying to run the rototiller up the right edge of mine and I am worn out!

Our hoophouse is 20 feet wide by 24 feet long with roll-up sides. The photos here are from last summer. There are two adults plus a child who is a tomato/cucumber/kohlrabi/green bean eatin' monster!

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Below is a photo of the interior last year. Green beans are growing up a support, swiss chard and onions behind, and a tomato plant at the right side. We attached netting to the sides to try to keep cabbage white butterflies off my precious brassicas.

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Rollerhooks are a concept that I stumbled across in Eliot Coleman's book and implemented last summer. Aircraft cable is attached to the supports of the hoophouse and tensioned using a turnbuckle. Once that's done, one suspends rollerhooks from the cable and uses them to support vertical plant growth. Last year I was late getting it implemented but still grew some of the tomatoes and green peppers up them--this year I'll add the green beans to this technique and who knows what else.

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Thanks for the informative post and wonderful pictures. I recently attended a great class on seed starting. DH is capable of doing the building. We love having a garden and look forward to having more fresh vegetables all year.

huisjen: hope you are reading. My husband likes your design the best because it is the easiest and least expensive for him to build. But, he thinks if we have 2 large doors on the ends, we won't need roll-up sides. We're going with 16x24 and live near Concord NH so must have similar climate to you in ME.
Do you have roll up sides? I am concerned about how hot it will get in August when I'll be planting fall crops

I don't have roll up sides. What I have is a high vent in the end opposite the door. It pivots on a bar.
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I've been thinking an automatic opener would be a good idea. It does get hot in there, but the tomatoes don't complain. The door stays open, with a screen over it, all summer. The two openings are at different enough height that chimney effect works pretty well.

huisjen: I am planning on building a backyard greenhouse similar to your design and was curious as to what material (strapping) you used for the bows . Where did you get it ? It almost looks like 1"x4"s spaced by 2x4s on edge but , I am not 100% sure of it . Thanks for your help ...

It's wood strapping from Home Despot. It costs something like 20 cents a lineal foot. Dimensions are 2 1/2" x 3/4". Small tight knots are fine. Big knots are a problem.

Sorry, almost forgot: Yes, it's blocks of 6" 2x4 between the strapping, spaced 18" on center, attached with two 3" screws through each side, so (3/4"+3/4"+2 1/2"=5") they overlap by an inch in the center of the block. If the block eventually splits, the screws will still hold it solid. In the words of my old shop teacher, "Always lubricate when you screw". Just keep a wet bar of soap near you and rub the screw across it just before driving it.

Thanks for the info huisjen ...

THANKS huisjen esp for the mention of screen doors since I should have remembered that it will be a good idea to keep critters out of the place during the summer esp since we had to outwit winged and/or little strawberry thieves last summer. Great photo of vent.

Have seeds etc ordered. Now I know why some people put their hoop house up in the fall or late summer.