Lufttäthetsmått

Lufttäthetsmått refers to a measurement of how airtight a building or construction is. It quantifies the amount of uncontrolled air leakage that passes through the building envelope. This leakage can occur through cracks, gaps, and penetrations in walls, floors, roofs, and around windows and doors. High levels of air leakage can lead to significant heat loss in winter and heat gain in summer, increasing energy consumption for heating and cooling.

The measurement is typically expressed as a value related to airflow rate per unit area or volume at a specific pressure difference, often measured in cubic meters per hour per square meter (m³/h/m²) or air changes per hour (ACH). A common method for assessing lufttäthetsmått is a fan pressurization test, also known as a blower door test. In this test, a powerful fan is used to create a pressure difference between the inside and outside of the building, and the amount of air required to maintain this pressure is measured.

Good air tightness is crucial for energy efficiency, as it helps to minimize unwanted heat transfer and reduce the load on heating and cooling systems. It also contributes to improved indoor air quality by preventing the ingress of unconditioned, potentially polluted outside air and by ensuring that mechanical ventilation systems function as intended. Conversely, excessive air leakage can lead to drafts, discomfort, and potential moisture problems within building structures due to condensation. Building regulations in many regions specify maximum permissible levels of air leakage for new constructions.