Courtesy Box Shell

If done well, air-sealing has a positive impact on occupant comfort, energy efficiency, and indoor air quality, but it also can add to the cost of a project in labor, materials, and time. One of the peskiest places to air seal is around electrical boxes in exterior walls but a new product developed by two architects could simplify the process, reports Green Building Advisor's Scott Gibson.

The Box Shell is a cardbard form that wraps around an electrical box. The form is slightly larger than the box, creating a small gap on the sides and a space at the back that is filled with expanding foam to air-seal and insulate. Here's the lowdown:

The Box Shell is installed after wiring has been roughed in and before cavity insulation is placed in the wall. After drywall goes up, the installer inserts the nozzle of a can of expanding latex foam between the electrical box and the form and fills the gap around the box and the space behind it with foam. It's the foam, not the box itself, that creates the seal.

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