The oldest way to use solar energy is to get direct gain from the sun’s rays, this is passive solar energy.
In order to make the sun’s rays benefit the building as much as possible, solar energy must be taken into account from the architectural conception (double façades, south aspect, glazing surfaces, etc.). Thermal insulation plays an important part to optimize the proportion of the passive solar contribution in the heating and lighting of a building.
In a passive solar house, passive solar contribution allows to save a lot of energy. In bioclimatic buildings, solar energy can heat the building partly or even entirely for a virtually nil proportional cost.