A key element to building an energy-efficient home is minimizing airflow and heat transfer. That means paying extra close attention to wall assemblies, especially in problem areas where wall sections face unconditioned spaces. Examples include attic knee walls, skylight wells, the space behind gas fireplace inserts, and behind showers and tubs on exterior walls.

Traditional wall assemblies are five-sided structures, but considerable gains can be made by opting for six-sided assemblies. It’s a relatively simple enhancement that dramatically increases home efficiency and comfort. And it’s also one of the energy-saving features required for EPS^TM, Energy Trust’s performance score for high-efficiency homes built above code.

In order to stop airflow and reduce heat transfer, walls need interior and exterior rigid or semi-rigid air barriers, often in the form of gypsum board, OSB, plywood, thermoply and rigid insulation. For the wall to be most efficient, the air barrier and insulation must also be aligned to work in tandem—six-sided wall assemblies make this possible.

With a traditional five-sided assembly, there’s a bottom plate, two studs and a top plate. Drywall and sheathing make up the other sides. While insulation fills the gaps between studs, heat transfer can occur when a side of the assembly is open to air and enables it to move through the insulation. The six-sided assembly solves this issue and simply requires adding a rigid or semi-rigid air barrier on the side of the wall assembly that’s not boxed in.

The combination of six-sided assemblies and properly installed insulation brings many benefits, including lower energy use, less demand on the heating and cooling system and comfortable, even temperatures throughout the home.

Six-sided assemblies meet the EPS requirement for fully aligned air barriers with insulation, and will help improve a home’s energy score. Download Energy Trust’s EPS Field Guide and watch training videos for more information on this and other energy-saving EPS requirements.