Poly house and greenhouse is actually the same thing. Traditionally the Greenhouses were constructed on wooden frame glass was used. On advent of plastic technology it became possible to replace glass with plastic material. Polly thin material being most popular, the Greenhouse is now called Poly house.
Thus the modern Greenhouses normally are building on steel frame and are clad with plastic, which is fixed to frame with Aluminum grippers. The crop is to be produced in polyhouse, the polyhouse function as device that protects the crops against wind, rain, precipitation, radiation and temperature.