The study is focused on the decreasing of oriented strand boards air permeability using paints.  The oriented strand boards /3 (classification according to EN 300) of 12 mm thickness was chosen for the measurement. Nine different paints were applied in one layer on one side of boards. The difference in air permeability of unpainted and painted boards was defined as paint impact in %. Paint impact ranged from 1.9 % to 78.6 %. Furthermore, the air permeability of 15 and 22 mm thick oriented strand boards /3 boards from another producer exhibiting better properties has been measured to compare. The best results of paint impact were obtained for latex paint (paint impact 78.6 %) and penetration 1 (paint impact 66.4 %). Decreasing of the air permeability of oriented strand boards applied in low-cost constructions by using inexpensive paints could significantly improve the insulating properties of the wall structure and thus contribute to the development of the concept of low-cost passive building.