An under carpet heat shield/floor pan insulator is provided for a vehicle. The shield/insulator includes an acoustical and thermal insulating layer of polymer fiber that shows no signs of any thickness increase, delamination, deterioration or any undesirable effect which may affect performance for at least 330 hours when maintained at a temperature of at least approximately 150.degree. C. The shield/insulator may include a relatively high density, nonlaminate skin of polymer fiber and/or one or more facing layers constructed from polymer material.