Closed-cell spray foam has a closed cell structure which yields a rigid, hard foam and has been demonstrated to provide structural enhancement in certain buildings. These smaller cells trap an insulating gas, called a blowing agent. This blowing agent has a lower thermal conductivity than still air, increasing the insulation value, making it the best choice of insulation. Closed cell spray foam also qualifies as an air-barrier material from as little as 25mm thick, dramatically reducing air leakage through the building envelope, significantly lowering the building’s heating and cooling costs. The closed cell structure of makes it moisture-resistant and is the only spray foam that can be applied to cold materials to prevent condensation, again from as little as 25mm.