Ceiling-mounted air handling unit, including the housing, evaporative cooler, and fan, characterized by the housing being composed of insulated panels and anti-bridge-heat junction pieces, the anti-bridge-heat junction pieces comprising square tubes, slot plates, sealing strips, tees, and cover plates; the square tubes adjacent to the bottom of the side panels have rectangular grooves on opposite sides, with one groove having a small hat rim and chamfered bottom corners, and the other having a long hat rim lower than the small hat rim; the adjacent sides of the square tubes form rounded corners, with the right-angle structures inwardly folded and extended to form angle iron-type angle plates; the slot plates are panels with support plates and right-angle plates, where the support plates are vertically downward from the back of the slot plates and outwardly curled at the bottom, fixedly connected to the top of the panels to form a second small hat rim corresponding to the first small hat rim, fittingly holding the sealing strips; the right-angle plates are vertically downward from the upper part of the slot plates and inwardly folded to form right-angle bends, with the right-angle plates fittingly held in the long hat rim of the rectangular grooves on the opposite side; the support plates touch the bottom of the rectangular grooves; the slot plates form a large groove with the angle iron-type angle plate, where the insulated panels are installed inside the large groove; the slot plates form a small opening groove on the side with the small hat rim, where the sealing strips are installed, made of round-tube rubber; the first and second small hat rims hold the sealing strips in place.