We propose and experimentally implement a method, based on light-induced atomic desorption, for controlled generation of large sodium densities in siloxane-coated cells, kept at room temperature. An array of blue LEDs is used to desorb sodium atoms from the cell walls. The required atomic vapor density is achieved and stabilized by controlling the LED power through the feedback given by the sodium fluorescence. We show that sodium densities corresponding to about 400 K can be obtained and kept stable for a long time with less than 6 mW of LED light power. Moreover, this technique allows for precise vapor density modulation with a frequency of tenths of hertz, which is not possible using traditional heating methods.