diy hoop house this site has .pdf instructions - we made one (15x20) for a few hundred. There is a greenhouse supply place in Aurora (south of Canby) you can get the 5year plastic at. Get an off cut, cheaper!
"An Innovative Way For Heating Greenhouses Using Solar Energy During The Winter For Summer Crop Production" - “Wall of water” made of black PE water tubes. "...a simple, sustainable, nonpolluting, no emissions system for growing summer crops in winter by raising the temperature using only solar energy."