A hoop house (also called a polytunnel, hoop greenhouse, or hoophouse) is a greenhouse with a plastic roof wrapped over a flexible structure of hoops. The interior heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building faster than heat can escape the structure. The large hoops or bows can be made of metal, plastic pipe or even wood. The heavy greenhouse plastic "skin" is then stretched tight over the hoops and fastened to baseboards with strips of wood, metal, wire or even used irrigation tape and staples. Hoop houses are ultra-affordable, fast and cheap to build, and can extend a growing season by a couple month on each end. Click here for an extensive article on hoop houses if you'd like to read more.
http://www.onecommunityglobal.org/hoop-houses/
