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This paper concerns a new heat exchange and storage technique, which could be of special interest for passive cooling of buildings. With the purpose of delaying the meteorological oscillation carried by direct ventilation, controlled thermal phase-shifting is of special interest for passive cooling of buildings. By using a packed-bed with small and regular particle size and with enhanced convective exchange, it turns out possible to delay a sinusoidal temperature signal carried by an airflow, almost without dampening. This paper describes the physical phenomenon by way of a simple analytical model, and characterizes the effect of diverse perturbations. For the nightly temperature peak to be available in the middle of the day, complete phase-shift of the day/night oscillation could theoretically be reached with 0.6 m3 storage material per 100 m3/h airflow (slightly more than 2 m for a free air velocity as low as 0.1 m/s), provided good enough a convective exchange. Basing on this observation, prototypes for phase-shifting of the day/night oscillation are currently being developed at the University of Geneva, with very promising results.