This study developed a series of thermal simulations of buildings under the climatic conditions of 20 cities in Mexico. Thermal comfort was analyzed to examine how it is affected by variations in the solar reflectance and infrared emissivity of the exterior surface of a roof in reference housing. The percentage of uncomfortable hours per year was defined in terms of the PPD index (Predicted Percentage of Dissatisfied) as the fraction of time in which PPD > 20%. Optimal combinations were determined for each city, and it was found that the major effects of the solar reflectance and infrared emissivity occur in cities featuring climates whose ambient temperature is not far away from the comfortable temperature range. The maximum reduction of percentage of uncomfortable hours due to combined effect of solar reflectance and infrared emissivity ranging from 1.9% to 40.6%.