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Table 3 summarizes the results for test walls of red brick, tepetate, adobe and concrete, in both horizontal and vertical position, always considering an air flow parallel to the surface of the wall. Heat losses from the box enclosing the electric resistances were estimated for each test, considering metallic areas exposed to the air flow (from the steel base for walls) and using the convection heat transfer model described by the Eq. (6). Thus, heat losses were considered for the calculation of convective heat transfer coefficients, and ranged between 8.2 - 18.4% for tests with horizontal walls, and 11.6 - 25.9 for tests with vertical walls. Five different tests were made in each case, so that in Table 3 the standard deviation o of the estimated values of the convective coefficient is also included.