Energy wastage due to envelope leakage has been estimated in various countries through numerical simulations:
- in Belgium and in Germany, the energy impact has been calculated to be about 10% of the energy performance level for individual houses;
- estimates based on simulations on 9 real buildings in France lie between 0.5 and 15 kWh-pe/m2 per year (depending on climate, ventilation system type, and building configuration), with an average of 6.6 kWh-pe/m2, between “default” and excellent airtightness

For comparison purposes, in Belgium, France and Germany, the impact of good envelope airtightness is similar to that of solar collectors for domestic hot water.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12