A simple lumped parameter model is used to represent the time variations of internal temperature of a simple house, under hot, extreme weather variation, characteristic of northwestern Mexico. Results are validated by experimental work in a physical model without ventilation, with materials and building techniques typical of low-income family housing in this region. Energy balance in the present work is achieved by means of a system of three simultaneous differential equations, each depicting energy equilibrium in one of the basic building elements: the window glazing, the building materials, and inside air. With the mathematical model properly calibrated, heat transfer coefficients between walls, ceiling and windows are calculated. Passive techniques, such as window shading, orientation and thermal inertia, are evaluated by a normalized temperature index. Results show that interior temperature in the house can be reduced resulting in comfort increase. Then economical pertinence of studied passive elements can be evaluated.