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To obtain position-stabilized photon beams from the Photon Factory storage ring, our efforts were concentrated on two directions, one to minimize any disturbances causing the stored beam to move, and the other to suppress undesired beam motion by using feedback systems. This paper concerns one of the most disturbing cases, the diurnal beam position drift. The drift motion was suppressed with a global orbit feedback system, so that photon beam position was kept stable at all the beamlines. At the same time, some disturbances were reduced by investigating the cause and the mechanism of beam motion. The fact that the beam drift motion was closely correlated to the outdoor temperature variations led us to make a model simulation by taking account of the meteorological conditions around the building. It was proved that the building distortion due to the external thermal stress resulted in the diurnal beam motion. To minimize such distortion, it is suggested that one should insulate the building on the rooftop rather than underneath it as is usually done.