Tyvek's manufacturers do not advise using it for interior walls. It is created with the exterior walls in mind. You shouldn't use Tyvek on the interior walls for the following reasons:  1. Tyvek lets moisture through, which can condense on interior materials like plywood and drywall. The accumulation of moisture causes mold.  2. There are no leaks in the internal walls. Therefore, by placing Tyvek on the inner walls, you miss its advantages of water resistance.