Here's why:

* Material: Flannel is typically made from wool or cotton, both of which are poor conductors of electricity.

* Structure: The fibers in flannel are woven loosely, creating air pockets that further inhibit the flow of electricity.

However, it's important to remember:

* Moisture: If the flannel shirt becomes wet, its insulating properties will decrease significantly. Wet fabric conducts electricity much better than dry fabric.

* Specific Materials: Some flannel shirts may be made with synthetic fibers that have slightly different electrical properties.

Overall, a dry flannel shirt is a good insulator and will not readily conduct electricity.