The ventilation system of your home recycles air causing pressure changes throughout the house. These pressure changes force air under baseboards, cracks, expansion gaps, cavities of studs, leaks from ducting etc… Do not seal or block the 1/4″ gap in a way that prevents air from filtering underneath panels. When installing trim, it is best to raise the trim slightly above the finished flooring material, by approximately 1/8″, to help encourage airflow. For basement conditions, proper ventilation and a dehumidifier is recommended to control temperature and humidity levels.