IR Blocking
Greenhouse poly films with IR help trap heat radiant heat. For this reason, it is often called a thermal film. When sunlight enters, a lot of the energy can radiate out of standard film. If a greenhouse cover has IR additive, the heat will be trapped and will in-turn raise the overall temperature of the greenhouse. As an example, when a car is left in the sunlight, you will have just experienced the IR effect of your windshield. If your vegetation thrives in very warm environments, you may consider using IR plastic sheeting.
Another consideration with IR greenhouse sheeting is that it diffuses the sunlight with nearly the same transmission of a clear poly sheet. Although translucent film will diffuse direct sunlight also, the light transmision is more effective with an IR film.