Abstract: An apparatus for permitting venting through eaves and foundation walls at low temperature and which closes at high temperature includes a shape-memory alloy spring that has a first expanded state at the low temperature and a second contracted state at the high temperature. At high temperature the shape-memory alloy spring contract which, in turn, closes a pivoting louver thereby obstructing the passage of air. At low temperature, after overcoming hysteresis, the shape-memory alloy spring expands and a counterforce type of spring is then able to urge the louver back into the open position. This process can be repeated, if necessary, thereby eliminating the need for replacement of the apparatus after experience of the high temperature event has occurred.