A sheet for use in a heat exchange apparatus. The sheet includes a first vertical rib that extends in a first direction generally parallel to the vertical axis of the heat exchange apparatus, wherein said first vertical rib protrudes in a second direction out of the plane. The sheet also includes a second vertical rib that extends in the first direction along the sheet, substantially all the way between the first and second edges of the sheet generally parallel to the first vertical rib. The second vertical rib also protrudes in the second direction out of the plane. The sheet further includes a first horizontal rib that extends in a third direction along the sheet substantially all the way between the third and fourth edges of the sheet, wherein the first horizontal rib protrudes in a fourth direction opposite said second direction. The sheet additionally includes a second horizontal rib that extends in the third direction along the sheet substantially all the way between the third and fourth edges of the sheet generally parallel to the first horizontal rib. The second horizontal rib protrudes in a fourth direction opposite the second direction, into the plane and intersects said second vertical rib.