With the interior studs in place the in-wall electrical and plumbing must be completed before the drywall goes up. Wiring is required for lights, switches, plugs and Direct TV. Plumbing is required for the bathroom sinks, showers, toilets, bathtub, interior sprinkler system and radiant floor heating. Ducts are installed for the HRV ventilation system. This system exchanges stale inside air with fresher outside air. The Interior Gallery contains more pictures.