Luftskift

Luftskift is the process of exchanging indoor air with outdoor air in a built environment. It is a central concept in ventilation design and aims to control indoor air quality, moisture, odors, and carbon dioxide levels, as well as to influence thermal comfort.

Luftskift can occur through natural or mechanical means. Natural luftskift relies on openings such as windows and vents, driven by wind pressure and buoyancy from temperature differences. Mechanical luftskift uses fans and ducts to supply outdoor air and exhaust indoor air, and can be balanced to regulate both directions of flow. Advanced mechanical systems often include heat recovery or energy recovery to preserve energy while maintaining air exchange.

The rate of luftskift is typically expressed as air changes per hour (ACH) or in liters per second per person. A common calculation is ACH = Q/V, where Q is the volumetric airflow and V is the room volume. In practice, assessments may use tracer gas methods or CO2 concentrations as proxies for ventilation effectiveness. Standards and guidelines from bodies such as ASHRAE and European norms specify minimum ventilation rates for different building types and occupancies, balancing indoor air quality with energy use.

Implications of luftskift include its impact on health, comfort, and energy consumption. Adequate exchange reduces accumulation of pollutants, moisture, and odors, and lowers disease transmission risk in some settings. Excessive ventilation increases energy demand and can cause drafts or temperature fluctuations. Designers tailor luftskift to space usage, occupancy, outdoor climate, and building tightness, often employing control strategies that adjust airflow in real time.

Overall, luftskift is a key element of indoor environmental quality, linking air quality with energy efficiency in modern buildings.