Has anyone built a greenhouse by using standard roof trusses covered with plastic film. I have access to a number of 24' 7/12 pitch steel trusses that I'd like to put up and then use plastic film as a covering. My concern is that the plastic will bow enough near the eaves that snow will hang and form puddles. We get somewhere between 100' and 200"+ inches of snow in a year. This year nothing but a dusting yet.
Most likely wood furring strips screwed down. This was originally a bot house that we took down about 10 years ago. At that time it have corrugated steel roofing on frames that had some king of clip that held them on. We didn't salvage the roofing as usable because of its age(50+ year).
My biggest concern is how will plastic flm sag and develop pockets where snow can accumulate with disastrous results.
Since you want to use steel trusses, you could purchase steel cattle panels at a local farm supply and attach those to the trusses and then cover with a strong 4 year greenhouse film.
By doing this I would think that it would support the snow. Just a thought.
It is added expense, but using a double layer of plastic is probably your best bet. Then use several small squirrel cage blowers to inflate between the two layers. My parents had a similar width GH set up. They only used fir stripping to attach the plastic at ground level and on the ends. For wet heavy snows we had to sometimes beat the inside or scape the snow on the outside to get it sliding if it accumulated, but that was the only problem.