Against the background of increased global demands for energy efficiency, property owners should raise the standards of ductwork systems for ventilation, heating and air conditioning. This would not only save energy, but also mean lower installation costs, shorter assembly times and better air quality thanks to less leakage. The importance of energy-efficient buildings will increase in the future, not only due to rising electricity prices, but also due to increased environmental awareness. One example of this is the Kyoto Agreement, which indirectly forces countries to review their energy use with the aim of reducing carbon dioxide emissions. A current example of the latter is the energy directive from the EU, which basically increases the demands on energy planning and on the energy performance of buildings. One way of satisfying the stricter energy rules can be to make demands of airtight ductwork systems for ventilation.