According to the IRC, nonmetallic boxes can only be used with which type of wiring methods?

Nonmetallic boxes are specifically designed to be used with entirely nonmetallic sheaths, such as NM (nonmetallic sheathed cable), which consists of plastic insulation surrounding the conductors. This usage is based on safety standards laid out in the International Residential Code (IRC). The nonmetallic sheaths protect the conductors and help prevent any potential electrical faults.

Using nonmetallic boxes with nonmetallic sheathed cable ensures compatibility in terms of thermal expansion, moisture resistance, and overall integrity of the installation. Nonmetallic boxes lack the structural strength or grounding capabilities to adequately support wiring methods that rely on metallic sheaths, which could lead to safety hazards.

In contrast, other types of wiring methods would not be appropriate with nonmetallic boxes, as they may require different types of enclosures that provide additional grounding or support that nonmetallic materials do not offer.