Abstract: A solar energy heated structure, such as an occupied building or greenhouse, includes a walled structure enclosing space volume. A movable insulated panel with a reflective surface is pivotably supported within the space volume. In a first position the panel cooperates with an insulated portion of the walled structure to enclose a lower portion of the space volume containing the occupied portion or plant bed and prevents loss of heat therefrom. In a second position the panel is disposed in an upper portion of the space volume, so that solar energy entering the overall space volume through a light transmitting portion of the walled structure is reflected onto the solar energy user by the reflective surface of the panel.