A pier boot is fabricated for installation around a pier in the crawlspace of a building. The pier boot includes a substantially impermeable polymer sheet. The polymer sheet has a flange portion and two or more slits therein. The slits define flap portions of the polymer sheet, and the slits each have an end that defines a hinge in the polymer sheet. The pier boot is installed around a pier in order to optimize the seal around that pier when constructing a conditioned crawlspace.