This work comprises case studies of passive indoor climate control techniques, applied to a number of office buildings in Spain. The main objective of the work was to evaluate the effects of using indoor permeable coverings on energy savings, for the same indoor thermal comfort conditions. Previous studies have shown that permeable coverings will lead to optimal indoor comfort conditions, which depend on maximum and minimum monthly mean outdoor temperature and relative humidity values. This work shows that, both in summer and winter, indoor energy consumption decreases with the permeability of coverings. An energy saving potential of 3 kWh/m(2) per year may be achieved, which leads to the possibility of replacing mechanical HVAC by passive methods in mild climates, such as in Spain and Portugal. (C) 2009 Elsevier B.V. All rights reserved.