This experimental work addressed the thermal control a roof-top collective building antenna meant to control home equipment in smart buildings. The antenna was placed inside a concentric quasi-cylindrical cavity maintained at low temperature. Cooling was provided by a Water-Copper nanofluid saturated porous matrix placed between the antenna and the enclosure. The ratio of the thermal conductivity of the porous material to that of the water varied from 4 up to 41.2. The nanoparticles volume fraction varied between 0% and 5%. The main result was a new semi-empirical correlation that allows for the determination of the antenna's average surface temperature as a function of the governing parameters: ratios of nanofluid to water and porous media to water thermal conductivities, nanoparticles volume fraction, and Rayleigh number. The applicability of the correlation was illustrated for a practical application case. It was found that, for some cases, the proposed thermal control system improves power dissipation by a factor of 33% as compared with the case of pure water (2 kW versus 1.5 kW)