The best screen for a greenhouse depends on the specific needs of the greenhouse and the types of plants being grown. Some common types of screens used in greenhouses include shade cloth, insect netting, and frost cloth. Shade cloth can help regulate temperature and light, while insect netting can keep pests out. Frost cloth can help protect plants from freezing temperatures. It's important to choose a screen that is appropriate for the specific growing conditions and needs of the plants being cultivated.