The evaporator/elect.heat strip is part of the central heat pump unit. It is located near the kitchen, sits on the floor and is not open to the outside except for the condensation drain which is not restricted and drains to the outside. Yes the crawl space does extend under the whole house. There are four 35 sq inch vents and several bricks with holes for vents also. The crawl space is approx. 2,860 cubic inches. The crawl space walls are brick and block.