A condensing assembly for urging condensation of a vapour into a liquid has a vertically stacked modular array of horizontal condensation units exposed to a heat transfer medium. Each condensation unit has a cooling chamber, a plurality of hollow legs and necks accessing the cooling chamber to define a fluid passageway. An open or enclosed space between vertically opposed condensation units is created by coupling the necks and legs of opposed condensation units. Introduced vapour travels along the fluid passageways and through the cooling chambers for condensation into liquid, which then travels along the fluid passageways to a storage tank. A cooling loop in each cooling chamber increases condensation. Vapour funnels in the condensation units along the fluid passageway reduce vapour to liquid contact therealong. An inlet header provides additional cooling to the vapour prior to entering the condensation units.