That's what I was going to say!

Here is a link that might be useful: fava beans clip

I was going to say the same thing and if you grow them successfully you will hear this many times a day at market.

Any hoo, I would not grow them in a tunnel as they need cool/cold weather to be successful and if they get into temps above 85F they will not set beans and will start getting this fungus stuff that turns then black (the entire plant). Grow them outdoors and get them in the ground as early as you can and cover with row cover if it is going to get cold (under freezing) and they should be fine. They are hard to grow if you are in an area that does not have long cool spring such as they have in much of the EU they are very hard to grow. i gave up after 5 years as quality was usually not the best due to the weather warming up too much in April/May when they should have been setting beans and getting harvested.

The more I think about it, the more I am convinced the hoophouse won't the best place for favas, Boulderbelt just convinced me. This is my first foray into their world. I hadn't really planned on growing them, but my main restaurant customer wanted some. Said I'd give them a shot and see how they do. Incidentally, his restaurant does have Chianti from time to time. He may have a marketing idea for the spring menu. F..F..F.F..F..F..F