A parametric analysis and optimization method for passive heating and ventilation systems are developed, using the computational fluid dynamics (CFD) ANSYS design exploration and optimization tool. Moreover, a three-dimensional, quasi-steady CFD Fluent simulation is performed and validated against experimental results. For comparison, the thermal performance of a small-scale wooden room fitted with a solar chimney and an earth-to-air heat exchanger (EAHE) was experimentally evaluated in the cold season in Egypt, in March 14–22, 2016. A good agreement has been found between the experimental and simulated results, with error, correlation coefficient, and coefficient of determination average values of 7.3%, 96.5%, and 94%, respectively. Moreover, a parametric study is conducted to maximize the ventilation rate, using eight parameters for solar chimney configuration (width, length, air gap, inclination angle, and position) and EAHE design (pipe diameter, inlet position, and inlet height). It is found that the EAHE pipe diameter is the most sensitive parameter, followed by chimney height, and EAHE inlet height and position; the solar chimney inclination angle, width, and gap have also noticeable impacts. The optimum chimney inclination angle, length, width, and gap ranges are 30–35°, 1.94–1.97 m, 0.92–0.97 m, and 0.19–0.23 m, respectively