Abstract: An improved motor vehicle engine compartment [10] for protecting the engine from cold by retaining engine heat includes conventional side walls [11,12], hood [13] and cowling [14]. A front wall [16] adjacent the radiator [R] includes a series of movable louvers [22] for covering and uncovering a series of opeings [21]. A lower wall [17] includes a series of movable louvers [24] for covering and uncovering a series of openings [23]. Together these walls and the side walls, hood and cowling form a substantially hermetically sealed enclosure when the louvers are in the covering positions. Actuators [28,29], acting through connecting rods [26,27], move the louvers [22,24] to the covering and uncovering positions. A control circuit [40], responsive to low ambient temperature, high engine temperature and operation of the engine, controls the operation of the actuators [28,29].