In the face of escalating global average temperatures, it is urgent to identify mechanisms that can significantly curtail the emission of greenhouse gases. The construction industry plays a pivotal role in shaping these emissions, rendering the selection of environmentally conscious materials indispensable in the imminent future. In this context, attention is drawn to an interesting material from an ecological point of view: straw. Abundant as a natural byproduct exhibiting remarkable thermal properties, straw emerges as a good candidate for sustainable edification. In the present work, an in situ study of its thermal resistance is carried out, and it is found that it allows stable interior temperatures. The apparent thermal conductivity is analyzed in relation to the orientation of its fibers in the same building, and its low conductivity compared with traditional construction materials is confirmed. The relevance of this work lies in the fact that the building studied contains walls with different fiber orientations in the same room, with the same ambiental conditions. This ensures that the different thermal behaviors are exclusively due to the orientation of the fibers. When considering both orientations of the fibers, different values of thermal conductivity are discerned. Conductivity decreases when the direction of the heat flow is perpendicular to the fibers. However, due to the inherent geometry of the bales, their overall thermal behavior ultimately proves comparable.