“…Although no provisions were made on the present exchanger for "defrosting", this should be done for an actual installation.When the exchanger was constructed, provision was made for adding insulation. Downing(9) found that by insulatinghis heat exchanger there was a resultant increase in effective ness of the heat exchange. With his exchanger uninsulatedt he exhaust air gained heat from the stable air; thus, a greater temperature differential was maintained between the airs.…”