The Himachal Pradesh government is promoting farming inside modern greenhouses called polyhouses to improve the earning potential of farmers in the state, especially during the harsh winters. The economy of the hill state is highly dependent on agriculture, apart from hydroelectric power and tourism. But most of its farmers have small landholdings on hill slopes, and need to augment their incomes.  It is difficult to grow anything outdoors in the harsh Himalayan winters. So the government is now promoting polyhouse farming, especially for off-season cultivation.
Polyhouses are based on the greenhouse concept to let in heat and light, while preventing the heat from getting out. But instead of the glass on a greenhouse roof, polyhouses are made of cheaper polythene or plastic. Read more at http://www.freshplaza.com/news_detail.asp?id=35924