Wiring installation in a remodeling project usually begins by adding a box. All connections—whether splices or connections to terminals—must be made inside a code-approved box. (Some fixtures, such as fluorescent and recessed lights, have self-contained electrical boxes approved by most building departments.)
insulating a basement
Check with your building department to see whether basement insulation methods are acceptable. Some municipalities require metal boxes, which are more expensive but usually no more trouble to install.
In older basement floor insulation that use conduit or armored-cable sheathing as a grounding path, the boxes must be metal because they are part of the grounding system. Homes with NM or MC cable use green-insulated or bare copper wires for grounding and don't require metal boxes. However, some local codes call for metal boxes, which provide a more secure connection for the ground wire.
insulating basement walls
A remodel box has fittings that secure it to a finished wall. Plastic boxes have wings. Metal boxes feature expandable clips or bendable ears that hold them in the wall. Remodel boxes all have internal clamps that clasp the cable to the box.
New-work boxes install quickly in framing that has not been covered with drywall or plaster. To install most models, hold the box in place (the box should extend beyond the framing by the thickness of the wall material) and drive in two nails.
To make sure a box will not be overcrowded, always buy as big a box as will fit the space available. The cubic-inch capacity of electrical boxes is usually marked on the box or the store bin. To calculate whether a box will be crowded, use these figures: A 14-gauge wire takes up 2 cubic inches; a 12-gauge wire takes up 21/4 cubic inches. Count the fixture or device as one wire. For instance this box contains eight 12-gauge "wires." two blacks, two whites, three grounds, and one receptacle—for a total of 18 cubic inches.