Over the years, there has been a tremendous amount of innovation in the building industry—still, the ability to achieve a waterproof wall system still eludes design/construction professionals. If the wall is not properly designed, this moisture will remain trapped causing numerous issues, such as the corrosion of structural reinforcing, and the proliferation of rot and mold.
Continuous insulation (ci) has been a component of exterior wall assemblies for more than 40 years in North America and even longer in Europe. It has always been the smart way to design wall assemblies from the standpoint of energy conservation and water management. By minimizing energy loss caused by thermal bridging and the risk of condensation caused by water vapor diffusion, exterior ci can improve building durability and benefit the environment.
Initially, water vapor diffusion was seen as the likely culprit for condensation problems; designers and consultants spent hours running and analyzing wall assemblies using the dewpoint method. With such analyses came the concept the wall system should be tuned for maximum condensation resistance by altering or selecting the appropriate permeability of the wall components. However, to create a truly robust wall system with the greatest condensation resistance and drying potential, designers need to look at altering the temperature profile of the wall assembly by moving insulation as far as possible to the exterior of the wall.
The December 2013 issue of The Construction Specifier included the article, “Out of Sight, Not Out of Mind,” by Ram Mayilvahanan. The feature focused on expanded polystyrene (EPS) and included reference to a particular industry study. In response to the piece, we recently received the following e-mail from John Ferraro, executive director of the Extruded Polystyrene Foam Association (XPSA):