Electricity consumption in buildings is especially relevant in hot and humid countries, where mechanical systems are frequently used to provide thermal comfort. In the context of school buildings, thermal comfort plays an important role in the learning process. Our aim is to explore natural ventilation to find passive, low-cost, realistic solutions to improve thermal comfort by combining design elements. For that, we assess four designs of doors (rectangular closed door, rectangular open door, half shutter door, half-door), four designs of windows (sliding window, sliding window with upper pivot window, sliding window with ventilated sill, and sliding window with upper pivot window and ventilated sill), and four building orientations (ventilated fa & ccedil;ade orientated towards north, east, south, and west.). A 4$<^>3$3 factorial design of thermal simulations and 3-way ANOVA are conducted to evaluate the combined effect of the design elements on thermal comfort in a primary school classroom in Brazil's hot and humid climate. Statistics applied to the hottest scenario reveal that orientation, window, and the joint effect of windows and doors significantly improve thermal comfort. Our results reveal that standard window and door designs are ineffective in promoting natural ventilation in hot and humid regions. The ventilated sill, pivot window, and half-door appear as effective low-cost realistic solutions, decreasing the intensity and frequency of thermal comfort by up to 60% and 30%, respectively.