Energy savings. During cold season, air handling units operate mostly at maximum load. Thus, you keep good air quality at home while saving expensive heating energy. During the warm season the filter gets contaminated quicker by various organic and non-organic particles, such as insects, pollen, fluffs, dust, etc. Pressure drop through the filters increases and thus energy consumption of fans increases as well. We presented additional monthly energy expenses due to averagely contaminated filters in the chart below. As you may see in case of air handling units to apartments or small houses, such as Domekt 200 / 250 / 400 /450, Smarty, RIRS 400, FLEXIT UNI 2/ UNI 3, may cost up to 8 EURO if you live in “expensive energy” countries as Denmark or Germany. For the large house (RIS 700, Domekt 700) it may even cost up to 15 EURO.