I am not sure if someone else had this idea but I am planning to use tarp to build my greenhouse this April. For 50$ you get a a strong and durable cover for your greenhouse. I could buy the 250$ greenhouse cover but for 50$ you get a hell of a deal for something that is strong and durable.

key features:

                                                                                                                                       

• Made of 850-denier woven high-density polyethylene that's stronger and lighter than canvas

• Tear & mildew resistant, rot & waterproof; non-cracking in hot or cold weather

• Heat-sealed seams and rope reinforced hems for long wear

• Laminated on both sides with LDPE

• Rust-proof grommet every 3 feet for secure tie-down

• 20' x 20' size in natural transparent colour

Michal,
good for you !
Personally i think its wise to try it that way and see what happens, if the matreial dont work out you still have the frame set up already and can try  another material.
Just think if it works to your likeing with a heater you can have more storage room in winter if you choose im thinking .  ; )
Best Health

Great find. I frequent the Canadian-Tire stores but never saw it on shelves there! It will start giving me some ideas.

I'm not sure how political races go in Canada.  In Texas (and everywhere else in the U.S.) the candidates spend big bucks on signs to advertise themselves.  I've seen these signs as big as 4X8. They are printed on white corrugated plastic.  If you've seen the US Postal Service totes, it's the same material.  I always saw these as cheap (free) greenhouse cover material after the election, but don't really have the need in TX.

~james

My son told me this week that his friend working for one of the glass shop have lots of windows taken from renovation
sites sitting in the office yard. These windows goes for very cheap like "make an offer". I am going to check them out as
I need a green house.

Michal ,
From my greenhouse experience , I've found that where pvc pipe touches greenhouse plastic for some reason  the gh plastic degrades much faster than normal , the covering you talk about may have the same reaction. For instance we had grey plastic electrical conduit running along a hipboard and there a high quality 4 year rated plastic degraded and tore open along that entire 48 foot length within two years.
Talking to a greenhouse builder he mentioned that where plastic conduit touches plastic cover should be separated by duct tape or some kind of fabric, something to keep the degrading from happening.
You may also look into quality of light transmission of the covering you are considering if figs are to stay in your tunnel for full season and not just temporarily. Greenhouse plastic usually has 85 or 90 % light transmission, if you potential covering gets a lot less than that then it functions as a shade house in terms of light and quality of growth will be more weak like indoors with warm temps and poor light. I've found that gh plastic is usually worth the price even in the short run. We are lucky enough here in NH to have a greenhouse builder who will cut you a piece of plastic the size you need instead of selling you a whole roll.
I miss my greenhouses. May yours give you tons of fruit.
Best ,
Kerry
Zone 5a

Here is an interesting website for small pipe benders for those who would like to use metal conduit.
http://www.lostcreek.net/  Lost Creek Greenhouse Systems
I built a small take off version out of several layers of plywood and screwed to my wooden barn floor , for bending 10 foot lengths of 1/2 inch metal conduit into 6 foot wide hoops for the garden.
Johnny's Seeds in Maine now carries Lost Creeks pipe benders.
Kerry

Paully: good idea I wish I had a could go to that kind of a place!

James: With minority governments for the last few years we had plenty of opportunities! Unfortunately, I missed all of them. They also use the same plastic material.


Kerry: Thanks for adding the extra information. I am fully aware that this will not be the same thing as a the ''real deal''. I had a a close look at it when I was at the store and int was transparent enough to my taste. Jon in Fredericton is using a winter car shelter as a greenhouse and the tarp on his car shelter surely has less light transmission then the one at Canadian tire ( See his Video).

If this tarp lasts only two years I will be a ''happy camper''.  Your tip for covering the PVC with something to prevent degradation is a good idea and I will surely do it. 

Michal, If heavy snow load is a consideration, PVC might be a problem.  It seems rigid, but will bend under a heavy load.  Same holds true for aluminum and even steel (this from experience), but at greater loads.  It might be worth looking into the economics of steel conduit that Kerry posted about.