The invention relates to a fiberglass material manufacture method and facility, were in molten glass is converted into fiberglass material via the steps of spinning, drawing, sizing, and collecting, followed by a step of producing a resulting fiberglass material that is then subjected to thermal desizing. The fumes from the melting furnace are used to preheat a combustion reagent from the melting furnace in two steps: a first step in which air is heated via heat exchange with the fumes, and a second step in which the combustion reagent is preheated via heat exchange with the hot air, the air then being used in the step of desizing the fiberglass material.