A great example of Aquaculture growing by friend Marc Laberge
A Solar Greenhouse can now be built without using any hoops for the interior film support. This approach is called the Wide Span system and it uses a high and low joist system. There is a joist (light weight ridge beam) forming the ridge (like Ross has along the peak of the tunnel) and these aluminum joists can span 30 or more feet. Similarly, there is another joist at the valley and the top of this joist forms the rain and melt water gutter. This is a raise gutter that you can walk under and should have a good 10 foot clearance. These low joists are also a couple or three feet deep and so the outer layer of film attaches to the top chords other the high and low joists and the inner layer of film attaches to the bottom chord of the joists. This creates a cavity space that is uniformly thick and this cavity can be filled with bubbles as need be. The high joist can have an interior clearance of 14 or 16 feet. The high/low joist roof is very strong and suitable for cold climates in high snow load zones.
For larger scale (areas exceeding 1000 M2) this approach would be my recommendation and I would like very much to explore with you the detailed design and also to welcome other commercial growers to join into this development effort. It is a very timely work and could really help to secure the prosperity of our greenhouse industry in Canada against the risks of the immediate future.
There is quite a bit of interest in this Sola Roof system and I would like to see extensive detailing of the construction at the Sola Roof Wiki in the Sola Roof Apps section for Commercial Growers. Attie and I have already made a good start on the 3D drawings of the Wide Span greenhouse structure. I am certain that Marcin and others in the midwest USA will support this project. This joist Sola Roof system is called the Wide Span greenhouse. The other options are the Single Hoop Frame? and Double Hoop Frame? systems for smaller scale tunnel greenhouse structures for Family Farm or homesteading applications. Anyone who would like to participate in the further development of these various applications can send me an email and I will provide information for joining the Wiki team. We have a sign in system now to deter spam. This is very much the same as at the Yahoo forum. Everyone is welcome to participate - there are no "qualifications" - just enthusiasm for pioneering our sustainable future.