Crawl Space Repair - EverLast Crawlspace Door

This crawlspace door is specially designed to have an airtight seal when closed. An EverLast door is recommended for a few reasons: 1. It pretty much lasts forever. Since it is made of plastic it will not rot, and 2. The airtight seal it creates. Why encapsulate your whole crawlspace and then keep your old, rotting crawlspace door that lets outside air in?