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Several dairy farms in Saxony (east of Germany) have old gutter-connected barns which are encountering several problems and they are: very low ventilation rates, non-uniformed air distribution, heat stress in summer, and high emission rates of harmful gases. A solution was suggested which is reconstructing the roofs of old gutter-connected dairy barns by modifying the roof design, increasing the cowshed height and the roof slope angle. Accordingly, a new roof was designed. In order to implement this new roof design, rigorous theoretical calculations were carried out to predict the possible indoor bioenvironment enhancement which was determined by estimating the following parameters: air exchange rate, indoor temperature, and temperature difference between indoor and outdoor temperatures. Furthermore, the area of adjustable air inlets and outlets and width of open ridges were specified. The airflow profile was then predicted. In order to achieve this task, a dairy farm (1300 cows) located in Saxony (east of Germany) and having old gutter-connected barns was considered to carry out the investigations, where the design of the selected dairy barns represents a widespread design in eastern Germany. The results of this study are being implemented for retrofitting the dairy barns and will be then implemented as extension and outreach for the other farms. The required information and data were acquired from the dairy farm under consideration, e.g.: design of the old barns, dimensions of all walls and air inlets and outlets, types and specifications of the construction materials, weather conditions and climate data, and farmstead layout and the other buildings that surround of the barns under consideration. The theoretical calculations of the different design parameters and bioenvironment were carried out using the heat balance, and the combined effects of wind pressure and thermal buoyancy forces. Afterwards, the results of the theoretical calculations of the suggested retrofitting design were compared with the actual values of the existing barns. The results show that the air exchange rates were 9 h-1 and 30.3 h-1 for the existing barns and the planned barns, respectively. The temperature differences (outdoor to indoor) were 1.4 oC and 6.6 oC for the existing barns and the planned barns, respectively. The area of air inlets in the windward side is 159.24 m2 for the existing barns, and it is recommended to be increased to 263 m2; consequently, the air exchange rate is anticipated to increase to 50.1 h-1. The width of each open ridge is 50 cm for the existing barns, and it is recommended to be enlarged to 70 cm in the planned reconstruction. The space volume is 45.2 m3 per cow in the existing barns and is enlarged to 63 m3 per cow according to the retrofitting design. The slope of the existing roofs is 5.7o, and it is recommended to be increased to 15o in the new roof design. Further technical notes and recommendations have been suggested by this study regarding the housing design, location of the different air openings, and dairy herd management.