So apparently my sister is moving in with her friend in the future. Two married couples renting a house and coexisting. Sister's friend is very into gardening. Had a family farm before she went to Japan. Now she's back, living with her husband, and enjoying life. When they find a place and move in, they plan on gardening in the back yard. I don't need help making raised beds. That's all easy. Different ways to heat the greenhouse and watering it is also planned. My question though is the greenhouse material. I was thinking of using the same stuff used for super shelters. The clear drop cloth. And I will still use that if it's the best bet. But what are some good affordable options for trapping in the heat for a greenhouse?