<p>The efficiency of a regenerative heat exchanger with an intermediate coolant and drop irrigation under winter operating conditions has been experimentally studied. It was found that the temperature efficiency of the heating and cooling columns increased with an increase in the packing irrigation density from 0.11 to 0.20 kg/(m²·s). The maximum temperature efficiency of 71 % for the heating column was obtained at an irrigation density of 0.21 kg/(m²·s). In the cooling column of the heat exchanger, the air flow from the room was cooled, and moisture was condensed there. In the heating column of the heat exchanger, the opposite process of intense evaporation of moisture and humidification of the air flow entering the room was observed. The maximum humidity efficiency of the heating column was about 80% at a packing irrigation density of 0.17–0.25 kg/(m²·s).</p>