This heavy plastic tent allows the exterior of Amazing Space to be heated so work can continue. And what’s up next is the air/vapor/moisture barrier. Exciting, right? And oh-so-critical. Modern buildings provide extraordinarily good air exchange and climate (that’s a euphemism for humidity, not just temperature) control systems, but those systems can only do their job if the envelope is snug. The barrier prevents exterior moisture from sneaking inside, rotting wood and creating mold issues.