Tilluft

Tilluft is the air that is introduced into a building’s ventilation system and delivered to occupied spaces to ensure indoor air quality and comfort. In modern ventilation, tilluft is typically outdoor air that is filtered, tempered, and distributed through ducts by a mechanical system, and it is balanced with frånluft (exhaust air) to maintain air exchange.

The tilluft can be conditioned to match indoor conditions. Heating or cooling may be applied to maintain a comfortable temperature, and filtration removes dust, pollen and other pollutants. In energy‑efficient installations, tilluft is preconditioned by a heat recovery system that exchanges heat with the outgoing air, reducing energy use while preserving air quality.

Delivery and distribution are achieved through supply diffusers or grilles in rooms, with fans and dampers controlling flow. Proper design aims for even distribution, minimal drafts, and avoidance of condensation or high humidity. In balanced mechanical ventilation the amount of tilluft equals the amount of frånluft, while other systems may rely on exhaust or mechanical supply alone.

System varieties include balanced mechanical ventilation with heat recovery, demand-controlled ventilation using sensors (such as CO2 or humidity), and natural or hybrid approaches in some buildings. Compliance with national or regional building codes often sets minimum fresh air rates and filtration requirements to maintain indoor air quality.

Maintenance is essential for tilluft quality and energy efficiency. Regular filter replacement, cleaning of ducts, and inspection of fans, dampers, and diffusers help prevent pollution, odors and mold growth. Overall, tilluft is central to indoor air quality, comfort and energy performance in contemporary buildings.