Ok, I need to know if they either prevent conduction, convection or radiation . I also need to know how they prevent these thermal energy transfer mechanisms (conduction,radiation and convection) from occuring.
Tall trees: If you have tall trees around your house, your house will be cooler because of the shade. The trees are blocking radiation from the sun, and to a lesser extent stopping convection to the air around the house by acting as a wind block. The air around your house removes heat through open, free convection. Polystyrene: The polystyrene panel itself has less conduction than other materials because it is less dense. Conduction is essentially shaking the atoms of the materials. Less dense things typically have less atoms to shake. (There are exceptions). But if you are talking about a dropped ceiling (with the panels haning from the real ceiling in the metal grid) as a whole system, there is more to it than that. Without the panels, you would lose heat to your roof (and the world outside) by convecting from your room to the ceiling, CONDUCTING through the ceiling, and convecting to the world outside. Your sandwich would be: Outside world Ceiling Room air But a dropped ceiling adds some more layers in there, most importantly a space of dead air, which is an excellent insulator - similar to a thermapane window. Your sandwich would become: Outside world Ceiling Dead (not moving) air between polystyrene panels Polystyrene panels Room air The extra layer in the sandwich helps. Polystyrene makes a good insulator, but it would still work if you dropped a ceiling with metal panels because of the dead air. In heat and mass transfer problems, it is critical that when you ask the question, you define what the system boundary is. My answer is long because I don't know what that is in your question. Hope it helps.
Apr 14, 2017